Publications by authors named "Richard Helm"

70 Publications

Comparative Metabolomics of Fruits and Leaves in a Hyperdiverse Lineage Suggests Fruits Are a Key Incubator of Phytochemical Diversification.

Front Plant Sci 2021 30;12:693739. Epub 2021 Aug 30.

Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA, United States.

Interactions between plants and leaf herbivores have long been implicated as the major driver of plant secondary metabolite diversity. However, other plant-animal interactions, such as those between fruits and frugivores, may also be involved in phytochemical diversification. Using 12 species of , we conducted untargeted metabolomics and molecular networking with extracts of fruits and leaves. We evaluated organ-specific secondary metabolite composition and compared multiple dimensions of phytochemical diversity across organs, including richness, structural complexity, and variability across samples at multiple scales within and across species. Plant organ identity, species identity, and the interaction between the two all significantly influenced secondary metabolite composition. Leaves and fruit shared a majority of compounds, but fruits contained more unique compounds and had higher total estimated chemical richness. While the relative levels of chemical richness and structural complexity across organs varied substantially across species, fruit diversity exceeded leaf diversity in more species than the reverse. Furthermore, the variance in chemical composition across samples was higher for fruits than leaves. By documenting a broad pattern of high phytochemical diversity in fruits relative to leaves, this study lays groundwork for incorporating fruit into a comprehensive and integrative understanding of the ecological and evolutionary factors shaping secondary metabolite composition at the whole-plant level.
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http://dx.doi.org/10.3389/fpls.2021.693739DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8435686PMC
August 2021

Pre-breeding androgen and glucocorticoid profiles in the eastern hellbender salamander (Cryptobranchus alleganiensis alleganiensis).

Gen Comp Endocrinol 2021 Nov 6;313:113899. Epub 2021 Sep 6.

Virginia Tech, Department of Fish and Wildlife Conservation, Blacksburg, VA USA 24060, USA.

Seasonally breeding species exhibit cyclical changes in circulating steroid hormone profiles that correspond with changes to their reproductive behavior and ecology. Such information is critical to the conservation of imperiled and data-deficient species, such as the eastern hellbender salamander (Cryptobranchus alleganiensis alleganiensis). We determined changes in plasma testosterone (T), dihydrotestosterone (DHT), 11-ketotestosterone (11-KT), 11-ketoandrostenedione (11-KA), dehydroepiandrosterone (DHEA), cortisol, corticosterone, and progesterone (P) during a four-month period preceding breeding in adult male and female eastern hellbenders. This pre-breeding period is characterized by increased diel movement and aggression by both sexes, follicular development and yolk production in females, and sperm production, territoriality, and nest site establishment in males. In both males and females, we observed a progressive increase in circulating T and DHT during the pre-reproductive season, both peaking in August (17 days before breeding), but concentrations of both hormones were higher in males. Conversely, 11-KT was higher in females, but did not vary significantly by date. These results suggest that T and DHT are the predominant androgens in eastern hellbenders and are likely important regulators of reproductive processes in both males and females. The detection of significant quantities of DHT and 11-KT in females is particularly interesting, considering that unlike T, neither of these androgens can be converted to estrogens. Therefore, it seems possible that aggression or some aspect of reproduction in the female eastern hellbender may be directly mediated by androgen signaling. Baseline cortisol did not vary throughout the pre-breeding period but was higher in females than males, and also became highly variable in females leading up to breeding. Progesterone, 11-KA, DHEA, and corticosterone were rarely or never detected, and thus, do not appear to be important during the pre-reproductive season. This study provides a physiological framework for future studies of hellbender reproductive biology, which could ultimately be important for their conservation.
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http://dx.doi.org/10.1016/j.ygcen.2021.113899DOI Listing
November 2021

Sex-Specific Linear Polyubiquitination Is a Critical Regulator of Contextual Fear Memory Formation.

Front Behav Neurosci 2021 9;15:709392. Epub 2021 Jul 9.

School of Neuroscience, Virginia Polytechnic Institute and State University, Blacksburg, VA, United States.

Strong evidence supports that protein ubiquitination is a critical regulator of fear memory formation. However, as this work has focused on protein degradation, it is currently unknown whether polyubiquitin modifications that are independent of the proteasome are involved in learning-dependent synaptic plasticity. Here, we present the first evidence that atypical linear (M1) polyubiquitination, the only ubiquitin chain that does not occur at a lysine site and is largely independent of the proteasome, is critically involved in contextual fear memory formation in the amygdala in a sex-specific manner. Using immunoblot and unbiased proteomic analyses, we found that male (49) and female (14) rats both had increased levels of linear polyubiquitinated substrates following fear conditioning, though none of these protein targets overlapped between sexes. In males, target protein functions involved cell junction and axonal guidance signaling, while in females the primary target was Adiponectin A, a critical regulator of neuroinflammation, synaptic plasticity, and memory, suggesting sex-dependent functional roles for linear polyubiquitination during fear memory formation. Consistent with these increases, siRNA-mediated knockdown of , an essential component of the linear polyubiquitin E3 complex LUBAC, in the amygdala impaired contextual fear memory in both sexes without affecting memory retrieval. Collectively, these results provide the first evidence that proteasome-independent linear polyubiquitination is a critical regulator of fear memory formation, expanding the potential roles of ubiquitin-signaling in learning-dependent synaptic plasticity. Importantly, our data identify a novel sex difference in the functional role of, but not a requirement for, linear polyubiquitination in fear memory formation.
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http://dx.doi.org/10.3389/fnbeh.2021.709392DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8298817PMC
July 2021

Females, but not males, require protein degradation in the hippocampus for contextual fear memory formation.

Learn Mem 2021 08 15;28(8):248-253. Epub 2021 Jul 15.

School of Neuroscience, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA.

Strong evidence supports a role for protein degradation in fear memory formation. However, these data have been largely done in only male animals. Here, we found that following contextual fear conditioning, females, but not males, had increased levels of proteasome activity and K48 polyubiquitin protein targeting in the dorsal hippocampus, the latter of which occurred at chaperones or RNA processing proteins. In vivo CRISPR-dCas9-mediated repression of protein degradation in the dorsal hippocampus impaired contextual fear memory in females, but not males. These results suggest a sex-specific role for protein degradation in the hippocampus during the consolidation of a contextual fear memory.
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http://dx.doi.org/10.1101/lm.053429.121DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8284313PMC
August 2021

McpT, a Broad-Range Carboxylate Chemoreceptor in Sinorhizobium meliloti.

J Bacteriol 2021 08 9;203(17):e0021621. Epub 2021 Aug 9.

Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia, USA.

Chemoreceptors enable the legume symbiont Sinorhizobium meliloti to detect and respond to specific chemicals released from their host plant alfalfa, which allows the establishment of a nitrogen-fixing symbiosis. The periplasmic region (PR) of transmembrane chemoreceptors act as the sensory input module for chemotaxis systems via binding of specific ligands, either directly or indirectly. S. meliloti has six transmembrane and two cytosolic chemoreceptors. However, the function of only three of the transmembrane receptors have been characterized so far, with McpU, McpV, and McpX serving as general amino acid, short-chain carboxylate, and quaternary ammonium compound sensors, respectively. In the present study, we analyzed the S. meliloti chemoreceptor McpT. High-throughput differential scanning fluorimetry assays, using Biolog phenotype microarray plates, identified 15 potential ligands for McpT, with the majority classified as mono-, di-, and tricarboxylates. S. meliloti exhibited positive chemotaxis toward seven selected carboxylates, namely, α-ketobutyrate, citrate, glyoxylate, malate, malonate, oxalate, and succinate. These carboxylates were detected in seed exudates of the alfalfa host. Deletion of resulted in a significant decrease of chemotaxis to all carboxylates except for citrate. Isothermal titration calorimetry revealed that McpT bound preferentially to the monocarboxylate glyoxylate and with lower affinity to the dicarboxylates malate, malonate, and oxalate. However, no direct binding was detected for the remaining three carboxylates that elicited an McpT-dependent chemotaxis response. Taken together, these results demonstrate that McpT is a broad-range carboxylate chemoreceptor that mediates chemotactic response via direct ligand binding and an indirect mechanism that needs to be identified. Nitrate pollution is one of the most widespread and challenging environmental problems that is mainly caused by the agricultural overapplication of nitrogen fertilizers. Biological nitrogen fixation by the endosymbiont Sinorhizobium meliloti enhances the growth of its host Medicago sativa (alfalfa), which also efficiently supplies the soil with nitrogen. Establishment of the S. melilotialfalfa symbiosis relies on the early exchange and recognition of chemical signals. The present study contributes to the disclosure of this complex molecular dialogue by investigating the underlying mechanisms of carboxylate sensing in S. meliloti. Understanding individual steps that govern the S. meliloti-alfalfa molecular cross talk helps in the development of efficient, commercial bacterial inoculants that promote the growth of alfalfa, which is the most cultivated forage legume in the world, and improves soil fertility.
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http://dx.doi.org/10.1128/JB.00216-21DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8351632PMC
August 2021

An Updated Perspective on Chemotaxis to Alfalfa Flavonoids.

Front Microbiol 2020 23;11:581482. Epub 2020 Oct 23.

Department of Biological Sciences, Life Sciences I, Virginia Tech, Blacksburg, VA, United States.

The symbiotic interaction between leguminous plants and their cognate rhizobia allows for the fixation of gaseous dinitrogen into bioavailable ammonia. The perception of host-derived flavonoids is a key initial step for the signaling events that must occur preceding the formation of the nitrogen-fixing organ. Past work investigating chemotaxis - the directed movement of bacteria through chemical gradients - of , , and discovered chemotaxis to various organic compounds, but focused on chemotaxis to flavonoids because of their relevance to the symbiosis biochemistry. The current work sought to replicate and further examine () chemotaxis to the flavonoids previously thought to act as the principal attractant molecules prior to the initial signaling stage. Exudate from germinating alfalfa seedlings was analyzed for composition and quantities of different flavonoid compounds using mass spectrometry. The abundance of four prevalent flavonoids in germinating alfalfa seed exudates (SEs) was at a ratio of 200:5:5:1 for hyperoside, luteolin, luteolin-7-glucoside, and chrysoeriol. Using quantitative chemotaxis capillary assays, we did not detect chemotaxis of motile cells to these, and two other flavonoids identified in seed exudates. In support of these findings, the flavonoid fraction of seed exudates was found to be an insignificant attractant relative to the more hydrophilic fraction. Additionally, we observed that cosolvents commonly used to dissolve flavonoids confound the results. We propose that the role flavonoids play in chemotaxis is insignificant relative to other components released by alfalfa seeds.
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http://dx.doi.org/10.3389/fmicb.2020.581482DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7644916PMC
October 2020

Cellular Stoichiometry of Chemotaxis Proteins in .

J Bacteriol 2020 06 25;202(14). Epub 2020 Jun 25.

Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia, USA

Chemotaxis systems enable microbes to sense their immediate environment, moving toward beneficial stimuli and away from those that are harmful. In an effort to better understand the chemotaxis system of , a symbiont of the legume alfalfa, the cellular stoichiometries of all ten chemotaxis proteins in were determined. A combination of quantitative immunoblot and mass spectrometry revealed that the protein stoichiometries in varied greatly from those in and To compare protein ratios to other systems, values were normalized to the central kinase CheA. All chemotaxis proteins exhibited increased ratios to various degrees. The 10-fold higher molar ratio of adaptor proteins CheW1 and CheW2 to CheA might result in the formation of rings in the chemotaxis array that consist of only CheW instead of CheA and CheW in a 1:1 ratio. We hypothesize that the higher ratio of CheA to the main response regulator CheY2 is a consequence of the speed-variable motor in , instead of a switch-type motor. Similarly, proteins involved in signal termination are far more abundant in , which utilizes a phosphate sink mechanism based on CheA retrophosphorylation to inactivate the motor response regulator versus CheZ-catalyzed dephosphorylation as in and Finally, the abundance of CheB and CheR, which regulate chemoreceptor methylation, was increased compared to CheA, indicative of variations in the adaptation system of Collectively, these results mark significant differences in the composition of bacterial chemotaxis systems. The symbiotic soil bacterium contributes greatly to host-plant growth by fixing atmospheric nitrogen. The provision of nitrogen as ammonium by leads to increased biomass production of its legume host alfalfa and diminishes the use of environmentally harmful chemical fertilizers. To better understand the role of chemotaxis in host-microbe interaction, a comprehensive catalogue of the bacterial chemotaxis system is vital, including its composition, function, and regulation. The stoichiometry of chemotaxis proteins in has very few similarities to the systems in and In addition, total amounts of proteins are significantly lower. exhibits a chemotaxis system distinct from known models by incorporating new proteins as exemplified by the phosphate sink mechanism.
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http://dx.doi.org/10.1128/JB.00141-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7317046PMC
June 2020

The dynamic response of the Arabidopsis root metabolome to auxin and ethylene is not predicted by changes in the transcriptome.

Sci Rep 2020 01 20;10(1):679. Epub 2020 Jan 20.

Department of Biological Sciences, Virginia Tech, Blacksburg, VA, United States of America.

While the effects of phytohormones on plant gene expression have been well characterized, comparatively little is known about how hormones influence metabolite profiles. This study examined the effects of elevated auxin and ethylene on the metabolome of Arabidopsis roots using a high-resolution 24 h time course, conducted in parallel to time-matched transcriptomic analyses. Mass spectrometry using orthogonal UPLC separation strategies (reversed phase and HILIC) in both positive and negative ionization modes was used to maximize identification of metabolites with altered levels. The findings show that the root metabolome responds rapidly to hormone stimulus and that compounds belonging to the same class of metabolites exhibit similar changes. The responses were dominated by changes in phenylpropanoid, glucosinolate, and fatty acid metabolism, although the nature and timing of the response was unique for each hormone. These alterations in the metabolome were not directly predicted by the corresponding transcriptome data, suggesting that post-transcriptional events such as changes in enzyme activity and/or transport processes drove the observed changes in the metabolome. These findings underscore the need to better understand the biochemical mechanisms underlying the temporal reconfiguration of plant metabolism, especially in relation to the hormone-metabolome interface and its subsequent physiological and morphological effects.
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http://dx.doi.org/10.1038/s41598-019-57161-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6971091PMC
January 2020

Functional annotation of serine hydrolases in the asexual erythrocytic stage of Plasmodium falciparum.

Sci Rep 2019 11 26;9(1):17532. Epub 2019 Nov 26.

Department of Biochemistry, Virginia Tech, Blacksburg, VA, 24061, USA.

Enzymes of the serine hydrolase superfamily are ubiquitous, highly versatile catalysts that mediate a wide variety of metabolic reactions in eukaryotic cells, while also being amenable to selective inhibition. We have employed a fluorophosphonate-based affinity capture probe and mass spectrometry to explore the expression profile and metabolic roles of the 56-member P. falciparum serine hydrolase superfamily in the asexual erythrocytic stage of P. falciparum. This approach provided a detailed census of active serine hydrolases in the asexual parasite, with identification of 21 active serine hydrolases from α/β hydrolase, patatin, and rhomboid protease families. To gain insight into their functional roles and substrates, the pan-lipase inhibitor isopropyl dodecylfluorophosphonate was employed for competitive activity-based protein profiling, leading to the identification of seven serine hydrolases with potential lipolytic activity. We demonstrated how a chemoproteomic approach can provide clues to the specificity of serine hydrolases by using a panel of neutral lipase inhibitors to identify an enzyme that reacts potently with a covalent monoacylglycerol lipase inhibitor. In combination with existing phenotypic data, our studies define a set of serine hydrolases that likely mediate critical metabolic reactions in asexual parasites and enable rational prioritization of future functional characterization and inhibitor development efforts.
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http://dx.doi.org/10.1038/s41598-019-54009-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6879560PMC
November 2019

Effect of Osteopathic Cranial Manipulative Medicine on an Aged Rat Model of Alzheimer Disease.

J Am Osteopath Assoc 2019 Oct 15. Epub 2019 Oct 15.

Context: In the aging brain, reduction in the pulsation of cerebral vasculature and fluid circulation causes impairment in the fluid exchange between different compartments and lays a foundation for the neuroinflammation that results in Alzheimer disease (AD). The knowledge that lymphatic vessels in the central nervous system play a role in the clearance of brain-derived metabolic waste products opens an unprecedented capability to increase the clearance of macromolecules such as amyloid β proteins. However, currently there is no pharmacologic mechanism available to increase fluid circulation in the aging brain.

Objective: To demonstrate the influence of an osteopathic cranial manipulative medicine (OCMM) technique, specifically, compression of the fourth ventricle, on spatial memory and changes in substrates associated with mechanisms of metabolic waste clearance in the central nervous system using the naturally aged rat model of AD.

Results: Significant improvement was found in spatial memory in 6 rats after 7 days of OCMM sessions. Live animal positron emission tomographic imaging and immunoassays revealed that OCMM reduced amyloid β levels, activated astrocytes, and improved neurotransmission in the aged rat brains.

Conclusion: These findings demonstrate the molecular mechanism of OCMM in aged rats. This study and further investigations will help physicians promote OCMM as an evidence-based adjunctive treatment for patients with AD.
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http://dx.doi.org/10.7556/jaoa.2019.121DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8425714PMC
October 2019

Cortisol is the predominant glucocorticoid in the giant paedomorphic hellbender salamander (Cryptobranchus alleganiensis).

Gen Comp Endocrinol 2020 01 3;285:113267. Epub 2019 Sep 3.

Dept of Biology, Tufts University, Medford, MA 02144, USA.

Corticosterone is widely regarded to be the predominant glucocorticoid produced in amphibians. However, we recently described unusually low baseline and stress-induced corticosterone profiles in eastern hellbenders (Cryptobranchus alleganiensis alleganiensis), a giant, fully aquatic salamander. Here, we hypothesized that hellbenders might also produce cortisol, the predominant glucocorticoid used by fishes and non-rodent mammals. To test our hypothesis, we collected plasma samples in two field experiments and analyzed them using multiple analytical techniques to determine how plasma concentrations of cortisol and corticosterone co-varied after 1) physical restraint and 2) injection with adrenocorticotropic hormone (ACTH), the pituitary hormone responsible for triggering the release of glucocorticoids from amphibian interrenal glands. Using liquid chromatography-mass spectrometry, we found that baseline and restraint-induced plasma concentrations of cortisol were more than five times those of corticosterone. We then demonstrated that plasma concentrations of both glucocorticoids increased in response to ACTH in a dose-dependent manner, but cortisol concentrations were consistently higher (up to 10-fold) than corticosterone. Cortisol and corticosterone concentrations were not correlated with one another at basal or induced conditions. The extremely low plasma concentrations of corticosterone in hellbenders suggests that corticosterone could simply be a byproduct of cortisol production, and raises questions as to whether corticosterone has any distinct physiological function in hellbenders. Our results indicate that hellbenders produce cortisol as their predominant glucocorticoid, supporting a small and inconclusive body of literature indicating that some other amphibians may produce appreciable quantities of cortisol. We hypothesize that the use of cortisol by hellbenders could be an adaptation to their fully aquatic life history due to cortisol's ability to fulfill both mineralocorticoid and glucocorticoid functions, similar to its functions in fishes. Given the large number of amphibian species that are fully aquatic or have aquatic life stages, we suggest that the broadly held assumption that corticosterone is the predominant glucocorticoid in all amphibians requires further scrutiny. Ultimately, multi-species tests of this assumption will reveal the ecological factors that influenced the evolution of endocrine adaptations among amphibian lineages, and may provide insight into convergent evolution of endocrine traits in paedomorphic species.
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http://dx.doi.org/10.1016/j.ygcen.2019.113267DOI Listing
January 2020

Fasting differentially alters the hypothalamic proteome of chickens from lines with the propensity to be anorexic or obese.

Nutr Diabetes 2019 04 1;9(1):13. Epub 2019 Apr 1.

Virginia Tech, Department of Animal and Poultry Sciences, Blacksburg, VA, USA.

Background: The hypothalamus is the ultimate modulator of appetite and energy balance and therefore sensitive to changes in nutritional state. Chicks from lines selected for low (LWS) and high (HWS) body weight are hypophagic and compulsive eaters, respectively, and differ in their propensity to become obese and in their hypothalamic mRNA response to fasting.

Methods: As fasting-induced changes in hypothalamic proteins are unknown, we investigated the hypothalamic proteomes of 5-day old LWS and HWS chicks in the fed and fasted states using a label-free liquid chromatography-tandem mass spectrometry (LC-MS/MS) approach.

Results: A total of 744 proteins were identified in the chicken hypothalamus, and 268 differentially abundant proteins were identified among four pairwise comparisons. Ninety-five proteins were associated with the response to fasting in HWS chicks, and 23 proteins were associated with the response to fasting in LWS chicks. Fasting-responsive proteins in HWS chicks were significantly enriched in ATP metabolic processes, glyoxylate/dicarboxylate metabolism, and ribosome function. There was no enrichment for any pathways in LWS chicks in response to fasting. In the fasted and fed states, 159 and 119 proteins differed between HWS and LWS, respectively. Oxidative phosphorylation, citric acid cycle, and carbon metabolism were the main pathways associated with differences between the two lines of chicks. Enzymes associated with metabolic pathways differed between HWS and LWS in both nutritional states, including fumarase, aspartate aminotransferase, mitochondrial GOT2, 3-hydroxyisobutyrate dehydrogenase, chondrogenesis associated lipocalin, sialic acid synthase, arylamine N-acetyltransferase, pineal gland isozyme NAT-3, and succinate dehydrogenase [ubiquinone] flavoprotein subunit, mitochondrial.

Conclusions: These results provide insights into the hypothalamic metabolic pathways that are affected by nutritional status and the regulation of appetite and eating behavior.
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http://dx.doi.org/10.1038/s41387-019-0081-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6443654PMC
April 2019

Membrane Proteomes and Ion Transporters in and Dormant and Germinating Spores.

J Bacteriol 2019 03 25;201(6). Epub 2019 Feb 25.

Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia, USA

Bacterial endospores produced by and species can remain dormant and highly resistant to environmental insults for long periods, but they can also rapidly germinate in response to a nutrient-rich environment. Multiple proteins involved in sensing and responding to nutrient germinants, initiating solute and water transport, and accomplishing spore wall degradation are associated with the membrane surrounding the spore core. In order to more fully catalog proteins that may be involved in spore germination, as well as to identify protein changes taking place during germination, unbiased proteomic analyses of membrane preparations isolated from dormant and germinated spores of and were undertaken. Membrane-associated proteins were fractionated by SDS-PAGE, gel slices were trypsin digested, and extracted peptides were fractionated by liquid chromatography and analyzed by matrix-assisted laser desorption ionization-tandem time of flight mass spectrometry. More than 500 proteins were identified from each preparation. Bioinformatic methods were used to characterize proteins with regard to membrane association, cellular function, and conservation across species. Numerous proteins not previously known to be spore associated, 6 in and 68 in , were identified. Relative quantitation based on spectral counting indicated that the majority of spore membrane proteins decrease in abundance during the first 20 min of germination. The spore membranes contained several proteins thought to be involved in the transport of metal ions, a process that plays a major role in spore formation and germination. Analyses of mutant strains lacking these transport proteins implicated YloB in the accumulation of calcium within the developing forespore. Bacterial endospores can remain dormant and highly resistant to environmental insults for long periods but can also rapidly germinate in response to a nutrient-rich environment. The persistence and subsequent germination of spores contribute to their colonization of new environments and to the spread of certain diseases. Proteins of and were identified that are associated with the spore membrane, a position that can allow them to contribute to germination. A set of identified proteins that are predicted to carry out ion transport were examined for their contributions to spore formation, stability, and germination. Greater knowledge of spore formation and germination can contribute to the development of better decontamination strategies.
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http://dx.doi.org/10.1128/JB.00662-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6398275PMC
March 2019

Identification of MOS9 as an interaction partner for chalcone synthase in the nucleus.

PeerJ 2018 19;6:e5598. Epub 2018 Sep 19.

Department of Biological Sciences, Virginia Polytechnic Institute and State University (Virginia Tech), Blacksburg, VA, USA.

Plant flavonoid metabolism has served as a platform for understanding a range of fundamental biological phenomena, including providing some of the early insights into the subcellular organization of metabolism. Evidence assembled over the past three decades points to the organization of the component enzymes as a membrane-associated complex centered on the entry-point enzyme, chalcone synthase (CHS), with flux into branch pathways controlled by competitive protein interactions. Flavonoid enzymes have also been found in the nucleus in a variety of plant species, raising the possibility of alternative, or moonlighting functions for these proteins in this compartment. Here, we present evidence that CHS interacts with MOS9, a nuclear-localized protein that has been linked to epigenetic control of genes that mediate effector-triggered immunity. Overexpression of results in a reduction of transcript levels and a metabolite profile that substantially intersects with the effects of a null mutation in . These results suggest that the MOS9-CHS interaction may point to a previously-unknown mechanism for controlling the expression of the highly dynamic flavonoid pathway.
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http://dx.doi.org/10.7717/peerj.5598DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6151112PMC
September 2018

Sinorhizobium meliloti Chemoreceptor McpV Senses Short-Chain Carboxylates via Direct Binding.

J Bacteriol 2018 12 6;200(23). Epub 2018 Nov 6.

Virginia Tech, Department of Biological Sciences, Blacksburg, Virginia, USA

is a soil-dwelling endosymbiont of alfalfa that has eight chemoreceptors to sense environmental stimuli during its free-living state. The functions of two receptors have been characterized, with McpU and McpX serving as general amino acid and quaternary ammonium compound sensors, respectively. Both receptors use a dual Cache (lcium channels and motaxis receptors) domain for ligand binding. We identified that the ligand-binding periplasmic region (PR) of McpV contains a single Cache domain. Homology modeling revealed that McpV is structurally similar to a sensor domain of a chemoreceptor with unknown function from , which crystallized with acetate in its binding pocket. We therefore assayed McpV for carboxylate binding and for carboxylate sensing. Differential scanning fluorimetry identified 10 potential ligands for McpV Nine of these are monocarboxylates with chain lengths between two and four carbons. We selected seven compounds for capillary assay analysis, which established positive chemotaxis of the wild type, with concentrations of peak attraction at 1 mM for acetate, propionate, pyruvate, and glycolate, and at 100 mM for formate and acetoacetate. Deletion of or mutation of residues essential for ligand coordination abolished positive chemotaxis to carboxylates. Using microcalorimetry, we determined that dissociation constants of the seven ligands with McpV were in the micromolar range. An McpV variant with a mutation in the ligand coordination site displayed no binding to isobutyrate or propionate. Of all the carboxylates tested as attractants, only glycolate was detected in alfalfa seed exudates. This work examines the relevance of carboxylates and their sensor to the rhizobium-legume interaction. Legumes share a unique association with certain soil-dwelling bacteria known broadly as rhizobia. Through concerted interorganismal communication, a legume allows intracellular infection by its cognate rhizobial species. The plant then forms an organ, the root nodule, dedicated to housing and supplying fixed carbon and nutrients to the bacteria. In return, the engulfed rhizobia, differentiated into bacteroids, fix atmospheric N into ammonium for the plant host. This interplay is of great benefit to the cultivation of legumes, such as alfalfa and soybeans, and is initiated by chemotaxis to the host plant. This study on carboxylate chemotaxis contributes to the understanding of rhizobial survival and competition in the rhizosphere and aids the development of commercial inoculants.
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http://dx.doi.org/10.1128/JB.00519-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6222202PMC
December 2018

More than Rotating Flagella: Lipopolysaccharide as a Secondary Receptor for Flagellotropic Phage 7-7-1.

J Bacteriol 2018 10 10;200(19). Epub 2018 Sep 10.

Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA

Bacteriophage 7-7-1, a member of the family , infects the soil bacterium sp. strain H13-3. Infection requires attachment to actively rotating bacterial flagellar filaments, with flagellar number, length, and rotation speed being important determinants for infection efficiency. To identify the secondary receptor(s) on the cell surface, we isolated motile, phage-resistant sp. H13-3 transposon mutants. Transposon insertion sites were pinpointed using arbitrary primed PCR and bioinformatics analyses. Three genes were recognized, whose corresponding proteins had the following computationally predicted functions: AGROH133_07337, a glycosyltransferase; AGROH133_13050, a UDP-glucose 4-epimerase; and AGROH133_08824, an integral cytoplasmic membrane protein. The first two gene products are part of the lipopolysaccharide (LPS) synthesis pathway, while the last is predicted to be a relatively small (13.4-kDa) cytosolic membrane protein with up to four transmembrane helices. The phenotypes of the transposon mutants were verified by complementation and site-directed mutagenesis. Additional characterization of motile, phage-resistant mutants is also described. Given these findings, we propose a model for sp. H13-3 infection by bacteriophage 7-7-1 where the phage initially attaches to the flagellar filament and is propelled down toward the cell surface by clockwise flagellar rotation. The phage then attaches to and degrades the LPS to reach the outer membrane and ejects its DNA into the host using its syringe-like contractile tail. We hypothesize that the integral membrane protein plays an important role in events following viral DNA ejection or in LPS processing and/or deployment. The proposed two-step attachment mechanism may be conserved among other flagellotropic phages infecting Gram-negative bacteria. Flagellotropic bacteriophages belong to the tailed-phage order , the most abundant phages in the virome. While it is known that these viruses adhere to the bacterial flagellum and use flagellar rotation to reach the cell surface, their infection mechanisms are poorly understood. Characterizing flagellotropic-phage-host interactions is crucial to understanding how microbial communities are shaped. Using a transposon mutagenesis approach combined with a screen for motile, phage-resistant mutants, we identified lipopolysaccharides as the secondary cell surface receptor for phage 7-7-1. This is the first cell surface receptor identified for flagellotropic phages. One hypothetical membrane protein was also recognized as essential for infection. These new findings, together with previous results, culminated in an infection model for phage 7-7-1.
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http://dx.doi.org/10.1128/JB.00363-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6148473PMC
October 2018

Publisher Correction: 78,000-year-old record of Middle and Later Stone Age innovation in an East African tropical forest.

Nat Commun 2018 06 5;9(1):2242. Epub 2018 Jun 5.

Department of Archaeology, Max Planck Institute for the Science of Human History, Kahlaische Strasse 10, Jena, D-07745, Germany.

The originally published version of this Article contained an error in Fig. 3, whereby an additional unrelated graph was overlaid on top of the magnetic susceptibility plot. Furthermore, the Article title contained an error in the capitalisation of 'Stone Age'. Both of these errors have now been corrected in both the PDF and HTML versions of the Article.
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http://dx.doi.org/10.1038/s41467-018-04753-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5988799PMC
June 2018

Evaluation of Feruloylated and p-Coumaroylated Arabinosyl Units in Grass Arabinoxylans by Acidolysis in Dioxane/Methanol.

J Agric Food Chem 2018 May 18;66(21):5418-5424. Epub 2018 May 18.

Department of Biochemistry, and The Department of Energy's Great Lakes Bioenergy Research Center, The Wisconsin Energy Institute , University of Wisconsin , Madison , Wisconsin 53726 , United States.

The arabinosyl side chains of grass arabinoxylans are partially acylated by p-coumarate ( pCA) and ferulate (FA). These aromatic side chains can cross-couple wall polymers resulting in modulation of cell wall physical properties. The determination of p-coumaroylated and feruloylated arabinose units has been the target of analytical efforts with trifluoroacetic acid hydrolysis the standard method to release feruloylated and p-coumaroylated arabinose units from arabinoxylans. Herein, we report on a more robust method to measure these acylated units. Acidolysis of extractive-free grass samples in a dioxane/methanol/aqueous 2 M HCl mixture provided the methyl 5- O- p-coumaroyl- and 5- O-feruloyl-l-arabinofuranoside anomers ( pCA-MeAra and FA-MeAra). These conjugates were readily analyzed by liquid chromatography combined with both UV and MS detection. The method revealed the variability of the relative acylation of arabinose units by pCA or FA in grass cell walls. This methodology will permit delineation of hydroxycinnamate acylation patterns in arabinoxylans.
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http://dx.doi.org/10.1021/acs.jafc.8b01618DOI Listing
May 2018

78,000-year-old record of Middle and Later stone age innovation in an East African tropical forest.

Nat Commun 2018 05 9;9(1):1832. Epub 2018 May 9.

Department of Archaeology, Max Planck Institute for the Science of Human History, Kahlaische Strasse 10, Jena, D-07745, Germany.

The Middle to Later Stone Age transition in Africa has been debated as a significant shift in human technological, cultural, and cognitive evolution. However, the majority of research on this transition is currently focused on southern Africa due to a lack of long-term, stratified sites across much of the African continent. Here, we report a 78,000-year-long archeological record from Panga ya Saidi, a cave in the humid coastal forest of Kenya. Following a shift in toolkits ~67,000 years ago, novel symbolic and technological behaviors assemble in a non-unilinear manner. Against a backdrop of a persistent tropical forest-grassland ecotone, localized innovations better characterize the Late Pleistocene of this part of East Africa than alternative emphases on dramatic revolutions or migrations.
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http://dx.doi.org/10.1038/s41467-018-04057-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5943315PMC
May 2018

Characterization of the adult Aedes aegypti early midgut peritrophic matrix proteome using LC-MS.

PLoS One 2018 23;13(3):e0194734. Epub 2018 Mar 23.

Department of Entomology, Texas A&M University, College Station, Texas, United States of America.

The Aedes aegypti mosquito is the principal vector of arboviruses such as dengue, chikungunya, yellow fever, and Zika virus. These arboviruses are transmitted during adult female mosquito bloodfeeding. While these viruses must transverse the midgut to replicate, the blood meal must also reach the midgut to be digested, absorbed, or excreted, as aggregation of blood meal metabolites can be toxic to the female mosquito midgut. The midgut peritrophic matrix (PM), a semipermeable extracellular layer comprised of chitin fibrils, glycoproteins, and proteoglycans, is one such mechanism of protection for the mosquito midgut. However, this structure has not been characterized for adult female Ae. aegypti. We conducted a mass spectrometry based proteomic analysis to identify proteins that comprise or are associated with the adult female Ae. aegypti early midgut PM. Altogether, 474 unique proteins were identified, with 115 predicted as secreted. GO-term enrichment analysis revealed an abundance of serine-type proteases and several known and novel intestinal mucins. In addition, approximately 10% of the peptides identified corresponded to known salivary proteins, indicating Ae. aegypti mosquitoes extensively swallow their own salivary secretions. However, the physiological relevance of this remains unclear, and further studies are needed to determine PM proteins integral for midgut protection from blood meal derived toxicity and pathogen protection. Finally, we describe substantial discordance between previously described transcriptionally changes observed in the midgut in response to a bloodmeal and the presence of the corresponding protein in the PM. Data are available via ProteomeXchange with identifier PXD007627.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0194734PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5865745PMC
July 2018

Skeletal muscle O-GlcNAc transferase is important for muscle energy homeostasis and whole-body insulin sensitivity.

Mol Metab 2018 05 24;11:160-177. Epub 2018 Feb 24.

Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA. Electronic address:

Objective: Given that cellular O-GlcNAcylation levels are thought to be real-time measures of cellular nutrient status and dysregulated O-GlcNAc signaling is associated with insulin resistance, we evaluated the role of O-GlcNAc transferase (OGT), the enzyme that mediates O-GlcNAcylation, in skeletal muscle.

Methods: We assessed O-GlcNAcylation levels in skeletal muscle from obese, type 2 diabetic people, and we characterized muscle-specific OGT knockout (mKO) mice in metabolic cages and measured energy expenditure and substrate utilization pattern using indirect calorimetry. Whole body insulin sensitivity was assessed using the hyperinsulinemic euglycemic clamp technique and tissue-specific glucose uptake was subsequently evaluated. Tissues were used for histology, qPCR, Western blot, co-immunoprecipitation, and chromatin immunoprecipitation analyses.

Results: We found elevated levels of O-GlcNAc-modified proteins in obese, type 2 diabetic people compared with well-matched obese and lean controls. Muscle-specific OGT knockout mice were lean, and whole body energy expenditure and insulin sensitivity were increased in these mice, consistent with enhanced glucose uptake and elevated glycolytic enzyme activities in skeletal muscle. Moreover, enhanced glucose uptake was also observed in white adipose tissue that was browner than that of WT mice. Interestingly, mKO mice had elevated mRNA levels of Il15 in skeletal muscle and increased circulating IL-15 levels. We found that OGT in muscle mediates transcriptional repression of Il15 by O-GlcNAcylating Enhancer of Zeste Homolog 2 (EZH2).

Conclusions: Elevated muscle O-GlcNAc levels paralleled insulin resistance and type 2 diabetes in humans. Moreover, OGT-mediated signaling is necessary for proper skeletal muscle metabolism and whole-body energy homeostasis, and our data highlight O-GlcNAcylation as a potential target for ameliorating metabolic disorders.
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http://dx.doi.org/10.1016/j.molmet.2018.02.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6001359PMC
May 2018

Reconstructing Prehistoric African Population Structure.

Cell 2017 Sep;171(1):59-71.e21

McDonald Institute for Archaeological Research, Cambridge CB2 3ER, UK; British Institute in Eastern Africa, Nairobi 30710, Kenya.

We assembled genome-wide data from 16 prehistoric Africans. We show that the anciently divergent lineage that comprises the primary ancestry of the southern African San had a wider distribution in the past, contributing approximately two-thirds of the ancestry of Malawi hunter-gatherers ∼8,100-2,500 years ago and approximately one-third of the ancestry of Tanzanian hunter-gatherers ∼1,400 years ago. We document how the spread of farmers from western Africa involved complete replacement of local hunter-gatherers in some regions, and we track the spread of herders by showing that the population of a ∼3,100-year-old pastoralist from Tanzania contributed ancestry to people from northeastern to southern Africa, including a ∼1,200-year-old southern African pastoralist. The deepest diversifications of African lineages were complex, involving either repeated gene flow among geographically disparate groups or a lineage more deeply diverging than that of the San contributing more to some western African populations than to others. We finally leverage ancient genomes to document episodes of natural selection in southern African populations. PAPERCLIP.
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http://dx.doi.org/10.1016/j.cell.2017.08.049DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5679310PMC
September 2017

Reconstructing Asian faunal introductions to eastern Africa from multi-proxy biomolecular and archaeological datasets.

PLoS One 2017 17;12(8):e0182565. Epub 2017 Aug 17.

Max Planck Institute for the Science of Human History, Jena, Germany.

Human-mediated biological exchange has had global social and ecological impacts. In sub-Saharan Africa, several domestic and commensal animals were introduced from Asia in the pre-modern period; however, the timing and nature of these introductions remain contentious. One model supports introduction to the eastern African coast after the mid-first millennium CE, while another posits introduction dating back to 3000 BCE. These distinct scenarios have implications for understanding the emergence of long-distance maritime connectivity, and the ecological and economic impacts of introduced species. Resolution of this longstanding debate requires new efforts, given the lack of well-dated fauna from high-precision excavations, and ambiguous osteomorphological identifications. We analysed faunal remains from 22 eastern African sites spanning a wide geographic and chronological range, and applied biomolecular techniques to confirm identifications of two Asian taxa: domestic chicken (Gallus gallus) and black rat (Rattus rattus). Our approach included ancient DNA (aDNA) analysis aided by BLAST-based bioinformatics, Zooarchaeology by Mass Spectrometry (ZooMS) collagen fingerprinting, and direct AMS (accelerator mass spectrometry) radiocarbon dating. Our results support a late, mid-first millennium CE introduction of these species. We discuss the implications of our findings for models of biological exchange, and emphasize the applicability of our approach to tropical areas with poor bone preservation.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0182565PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5560628PMC
October 2017

Exogenous Auxin Elicits Changes in the Arabidopsis thaliana Root Proteome in a Time-Dependent Manner.

Proteomes 2017 Jul 10;5(3). Epub 2017 Jul 10.

Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, USA.

Auxin is involved in many aspects of root development and physiology, including the formation of lateral roots. Improving our understanding of how the auxin response is mediated at the protein level over time can aid in developing a more complete molecular framework of the process. This study evaluates the effects of exogenous auxin treatment on the root proteome after exposure of young seedlings to auxin for 8, 12, and 24 h, a timeframe permitting the initiation and full maturation of individual lateral roots. Root protein extracts were processed to peptides, fractionated using off-line strong-cation exchange, and analyzed using ultra-performance liquid chromatography and data independent acquisition-based mass spectrometry. Protein abundances were then tabulated using label-free techniques and evaluated for significant changes. Approximately 2000 proteins were identified during the time course experiment, with the number of differences between the treated and control roots increasing over the 24 h time period, with more proteins found at higher abundance with exposure to auxin than at reduced abundance. Although the proteins identified and changing in levels at each time point represented similar biological processes, each time point represented a distinct snapshot of the response. Auxin coordinately regulates many physiological events in roots and does so by influencing the accumulation and loss of distinct proteins in a time-dependent manner. Data are available via ProteomeXchange with the identifier PXD001400.
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http://dx.doi.org/10.3390/proteomes5030016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5620533PMC
July 2017

The hepatocyte proteome in organotypic rat liver models and the influence of the local microenvironment.

Proteome Sci 2016 20;15:12. Epub 2017 Jun 20.

Department of Biochemistry, Virginia Tech, Blacksburg, Virginia 24061 USA.

Background: Liver models that closely mimic the in vivo microenvironment are useful for understanding liver functions, capabilities, and intercellular communication processes. Three-dimensional (3D) liver models assembled using hepatocytes and liver sinusoidal endothelial cells (LSECs) separated by a polyelectrolyte multilayer (PEM) provide a functional system while also permitting isolation of individual cell types for proteomic analyses.

Methods: To better understand the mechanisms and processes that underlie liver model function, hepatocytes were maintained as monolayers and 3D PEM-based formats in the presence or absence of primary LSECs. The resulting hepatocyte proteomes, the proteins in the PEM, and extracellular levels of urea, albumin and glucose after three days of culture were compared.

Results: All systems were ketogenic and found to release glucose. The presence of the PEM led to increases in proteins associated with both mitochondrial and peroxisomal-based β-oxidation. The PEMs also limited production of structural and migratory proteins associated with dedifferentiation. The presence of LSECs increased levels of Phase I and Phase II biotransformation enzymes as well as several proteins associated with the endoplasmic reticulum and extracellular matrix remodeling. The proteomic analysis of the PEMs indicated that there was no significant change after three days of culture. These results are discussed in relation to liver model function.

Conclusions: Heterotypic cell-cell and cell-ECM interactions exert different effects on hepatocyte functions and phenotypes.
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http://dx.doi.org/10.1186/s12953-017-0120-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5480101PMC
June 2017

Enhanced Mucosal Defense and Reduced Tumor Burden in Mice with the Compromised Negative Regulator IRAK-M.

EBioMedicine 2017 Feb 3;15:36-47. Epub 2016 Dec 3.

Department of Biomedical Sciences and Pathobiology, VA-MD College of Veterinary Medicine, Blacksburg, Virginia 24061, United States. Electronic address:

Aberrant inflammation is a hallmark of inflammatory bowel disease (IBD) and colorectal cancer. IRAK-M is a critical negative regulator of TLR signaling and overzealous inflammation. Here we utilize data from human studies and Irak-m mice to elucidate the role of IRAK-M in the modulation of gastrointestinal immune system homeostasis. In human patients, IRAK-M expression is up-regulated during IBD and colorectal cancer. Further functional studies in mice revealed that Irak-m animals are protected against colitis and colitis associated tumorigenesis. Mechanistically, our data revealed that the gastrointestinal immune system of Irak-m mice is highly efficient at eliminating microbial translocation following epithelial barrier damage. This attenuation of pathogenesis is associated with expanded areas of gastrointestinal associated lymphoid tissue (GALT), increased neutrophil migration, and enhanced T-cell recruitment. Further evaluation of Irak-m mice revealed a splice variant that robustly activates NF-κB signaling. Together, these data identify IRAK-M as a potential target for future therapeutic intervention.
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http://dx.doi.org/10.1016/j.ebiom.2016.11.039DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5233813PMC
February 2017

Sinorhizobium meliloti chemotaxis to quaternary ammonium compounds is mediated by the chemoreceptor McpX.

Mol Microbiol 2017 01 11;103(2):333-346. Epub 2016 Nov 11.

Department of Biological Sciences, Life Sciences I, Virginia Tech, Blacksburg, VA, 24061, USA.

The bacterium Sinorhizobium meliloti is attracted to seed exudates of its host plant alfalfa (Medicago sativa). Since quaternary ammonium compounds (QACs) are exuded by germinating seeds, we assayed chemotaxis of S. meliloti towards betonicine, choline, glycine betaine, stachydrine and trigonelline. The wild type displayed a positive response to all QACs. Using LC-MS, we determined that each germinating alfalfa seed exuded QACs in the nanogram range. Compared to the closely related nonhost species, spotted medic (Medicago arabica), unique profiles were released. Further assessments of single chemoreceptor deletion strains revealed that an mcpX deletion strain displayed little to no response to these compounds. Differential scanning fluorimetry showed interaction of the isolated periplasmic region of McpX (McpX and McpX ) with QACs. Isothermal titration calorimetry experiments revealed tight binding to McpX with dissociation constants (K ) in the nanomolar range for choline and glycine betaine, micromolar K for stachydrine and trigonelline and a K in the millimolar range for betonicine. Our discovery of S. meliloti chemotaxis to plant-derived QACs adds another role to this group of compounds, which are known to serve as nutrient sources, osmoprotectants and cell-to-cell signalling molecules. This is the first report of a chemoreceptor that mediates QACs taxis through direct binding.
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http://dx.doi.org/10.1111/mmi.13561DOI Listing
January 2017

Amylin Amyloid Inhibition by Flavonoid Baicalein: Key Roles of Its Vicinal Dihydroxyl Groups of the Catechol Moiety.

Biochemistry 2016 08 27;55(31):4255-8. Epub 2016 Jul 27.

Department of Biochemistry, ‡Center for Drug Discovery, and §Translational Obesity Research Center, Virginia Polytechnic Institute & State University , Blacksburg, Virginia 24061, United States.

Amyloid formation of the 37-residue amylin is involved in the pathogenesis of type 2 diabetes and, potentially, diabetes-induced neurological deficits. Numerous flavonoids exhibit inhibitory effects against amylin amyloidosis, but the mechanisms of inhibition remain unclear. Screening a library of natural compounds uncovered a potent lead compound, the flavone baicalein. Baicalein inhibits amylin amyloid formation and reduces amylin-induced cytotoxicity. Analogue analyses demonstrated, for the first time, key roles of the vicinal hydroxyl groups on the A-ring. We provided mass spectrometric evidence that incubating baicalein and amylin leads to their conjugation, consistent with a Schiff base mechanism.
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http://dx.doi.org/10.1021/acs.biochem.6b00578DOI Listing
August 2016

Evolutionary correlations in flavonoid production across flowers and leaves in the Iochrominae (Solanaceae).

Phytochemistry 2016 Oct 10;130:119-27. Epub 2016 Jun 10.

Department of Ecology and Evolutionary Biology, University of Colorado-Boulder, Campus Box 334, Boulder, CO, 80309, USA.

Plant reproductive and vegetative tissues often use the same biochemical pathways to produce specialized metabolites. In such cases, selection acting on the synthesis of specific products in a particular tissue could result in correlated changes in other products of the pathway, both in the same tissue and in other tissues. This study examined how changes in floral anthocyanin pigmentation affect the production of other compounds of the flavonoid pathway in flowers and in leaves. Focusing on the Iochrominae, a clade of Solanaceae with a wide range of flower colors, liquid chromatography coupled with mass spectrometry and UV detection was used to profile and quantify the variation in two classes of flavonoids, anthocyanins and flavonols. Purple, red, orange and white-flowered Iochrominae produced all of the six common anthocyanidin types, as well as several classes of flavonols. Differences in anthocyanin and flavonol production were significantly correlated in flowers, particularly with respect to B ring hydroxylation pattern. However, these differences in floral flavonoids were not strongly related to differences in leaf chemistry. Specifically, most species made only flavonols (not anthocyanins) in leaves, and these comprised the two most common flavonols, quercetin and kaempferol, regardless of the color of the flower. These results suggest that shifts in flower color may occur without significant pleiotropic consequences for flavonoid production in vegetative tissues. Similar studies in other systems will be important for testing the generality of this pattern in other groups of flowering plants.
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http://dx.doi.org/10.1016/j.phytochem.2016.05.007DOI Listing
October 2016

Ancient crops provide first archaeological signature of the westward Austronesian expansion.

Proc Natl Acad Sci U S A 2016 06 31;113(24):6635-40. Epub 2016 May 31.

School of Archaeology, University of Oxford, Oxford OX1 2PG, United Kingdom; Department of Archaeology, Max Planck Institute for the Science of Human History, D-07743 Jena, Germany.

The Austronesian settlement of the remote island of Madagascar remains one of the great puzzles of Indo-Pacific prehistory. Although linguistic, ethnographic, and genetic evidence points clearly to a colonization of Madagascar by Austronesian language-speaking people from Island Southeast Asia, decades of archaeological research have failed to locate evidence for a Southeast Asian signature in the island's early material record. Here, we present new archaeobotanical data that show that Southeast Asian settlers brought Asian crops with them when they settled in Africa. These crops provide the first, to our knowledge, reliable archaeological window into the Southeast Asian colonization of Madagascar. They additionally suggest that initial Southeast Asian settlement in Africa was not limited to Madagascar, but also extended to the Comoros. Archaeobotanical data may support a model of indirect Austronesian colonization of Madagascar from the Comoros and/or elsewhere in eastern Africa.
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http://dx.doi.org/10.1073/pnas.1522714113DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4914162PMC
June 2016
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