Publications by authors named "Ketaki Bhide"

12 Publications

  • Page 1 of 1

Transcriptomics in Erigeron canadensis reveals rapid photosynthetic and hormonal responses to auxin herbicide application.

J Exp Bot 2020 06;71(12):3701-3709

Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN, USA.

The perception pathway for endogenous auxin has been well described, yet the mode of action of synthetic auxin herbicides, used for >70 years, remains uncharacterized. We utilized transcriptomics and targeted physiological studies to investigate the unknown rapid response to synthetic auxin herbicides in the globally problematic weed species Erigeron canadensis. Synthetic auxin herbicide application consistently and rapidly down-regulated the photosynthetic machinery. At the same time, there was considerable perturbation to the expression of many genes related to phytohormone metabolism and perception. In particular, auxin herbicide application enhanced the expression of the key abscisic acid biosynthetic gene, 9-cis-epoxycarotenoid deoxygenase (NCED). The increase in NCED expression following auxin herbicide application led to a rapid biosynthesis of abscisic acid (ABA). This increase in ABA levels was independent of a loss of cell turgor or an increase in ethylene levels, both proposed triggers for rapid ABA biosynthesis. The levels of ABA in the leaf after auxin herbicide application continued to increase as plants approached death, up to >3-fold higher than in the leaves of plants that were drought stressed. We propose a new model in which synthetic auxin herbicides trigger plant death by the whole-scale, rapid, down-regulation of photosynthetic processes and an increase in ABA levels through up-regulation of NCED expression, independent of ethylene levels or a loss of cell turgor.
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http://dx.doi.org/10.1093/jxb/eraa124DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7307852PMC
June 2020

Proteomic Analysis of 3T3-L1 Adipocytes Treated with Insulin and TNF-α.

Proteomes 2019 Oct 20;7(4). Epub 2019 Oct 20.

Purdue Proteomics Facility, Bindley Bioscience Center, Purdue University, West Lafayette, IN 47907, USA.

Insulin resistance is an indication of early stage Type 2 diabetes (T2D). Insulin resistant adipose tissues contain higher levels of insulin than the physiological level, as well as higher amounts of intracellular tumor necrosis factor-α (TNF-α) and other cytokines. However, the mechanism of insulin resistance remains poorly understood. To better understand the roles played by insulin and TNF-α in insulin resistance, we performed proteomic analysis of differentiated 3T3-L1 adipocytes treated with insulin (Ins), TNF-α (TNF), and both (Ins + TNF). Out of the 693 proteins identified, the abundances of 78 proteins were significantly different ( < 0.05). Carnitine parmitoyltransferase-2 (CPT2), acetyl CoA carboxylase 1 (ACCAC-1), ethylmalonyl CoA decarboxylase (ECHD1), and methylmalonyl CoA isomerase (MCEE), enzymes required for fatty acid β-oxidation and respiratory electron transport, and β-glucuronidase, an enzyme responsible for the breakdown of complex carbohydrates, were down-regulated in all the treatment groups, compared to the control group. In contrast, superoxide dismutase 2 (SOD2), protein disulfide isomerase (PDI), and glutathione reductase, which are the proteins responsible for cytoskeletal structure, protein folding, degradation, and oxidative stress responses, were up-regulated. This suggests higher oxidative stress in cells treated with Ins, TNF, or both. We proposed a conceptual metabolic pathway impacted by the treatments and their possible link to insulin resistance or T2D.
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http://dx.doi.org/10.3390/proteomes7040035DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6958341PMC
October 2019

Genome-wide identification of histone methylation (H3K9) and acetylation (H4K12) marks in two ecotypes of switchgrass (Panicum virgatum L.).

BMC Genomics 2019 Aug 22;20(1):667. Epub 2019 Aug 22.

Molecular Genetics and Epigenomics Laboratory, College of Agriculture and Related Sciences, Delaware State University, Dover, DE, USA.

Background: Histone modifications play a significant role in the regulation of transcription and various biological processes, such as development and regeneration. Though a few genomic (including DNA methylation patterns) and transcriptomic studies are currently available in switchgrass, the genome-wide distribution of histone modifications has not yet been studied to help elucidate gene regulation and its application to switchgrass improvement.

Results: This study provides a comprehensive epigenomic analyses of two contrasting switchgrass ecotypes, lowland (AP13) and upland (VS16), by employing chromatin immunoprecipitation sequencing (ChIP-Seq) with two histone marks (suppressive- H3K9 and active- H4K12). In this study, most of the histone binding was in non-genic regions, and the highest enrichment was seen between 0 and 2 kb regions from the transcriptional start site (TSS). Considering the economic importance and potential of switchgrass as a bioenergy crop, we focused on genes, transcription factors (TFs), and pathways that were associated with C4-photosynthesis, biomass, biofuel production, biotic stresses, and abiotic stresses. Using quantitative real-time PCR (qPCR) the relative expression of five genes selected from the phenylpropanoid-monolignol pathway showed preferential binding of acetylation marks in AP13 rather than in VS16.

Conclusions: The genome-wide histone modifications reported here can be utilized in understanding the regulation of genes important in the phenylpropanoid-monolignol biosynthesis pathway, which in turn, may help understand the recalcitrance associated with conversion of biomass to biofuel, a major roadblock in utilizing lignocellulosic feedstocks.
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http://dx.doi.org/10.1186/s12864-019-6038-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6704705PMC
August 2019

Comparative analysis of the root transcriptomes of cultivated sweetpotato (Ipomoea batatas [L.] Lam) and its wild ancestor (Ipomoea trifida [Kunth] G. Don).

BMC Plant Biol 2017 01 13;17(1). Epub 2017 Jan 13.

Department of Agriculture, University of Arkansas at Pine Bluff, Pine Bluff, Arkansas, USA.

Background: The complex process of formation of storage roots (SRs) from adventitious roots affects sweetpotato yield. Identifying the genes that are uniquely expressed in the SR forming cultivated species, Ipomoea batatas (Ib), and its immediate ancestral species, Ipomoea trifida (It), which does not form SRs, may provide insights into the molecular mechanisms underlying SR formation in sweetpotato.

Results: Illumina paired-end sequencing generated ~208 and ~200 million reads for Ib and It, respectively. Trinity assembly of the reads resulted in 98,317 transcripts for Ib and 275,044 for It, after post-assembly removal of trans-chimeras. From these sequences, we identified 4,865 orthologous genes in both Ib and It, 60 paralogous genes in Ib and 2,286 paralogous genes in It. Among paralogous gene sets, transcripts encoding the transcription factor RKD, which may have a role in nitrogen regulation and starch formation, and rhamnogalacturonate lyase (RGL) family proteins, which produce the precursors of cell wall polysaccharides, were found only in Ib. In addition, transcripts encoding a K efflux antiporter (KEA5) and the ERECTA protein kinase, which function in phytohormonal regulation and root proliferation, respectively, were also found only in Ib. qRT-PCR indicated that starch and sucrose metabolism genes, such as those encoding ADP-glucose pyrophosphorylase and beta-amylase, showed lower expression in It than Ib, whereas lignin genes such as caffeoyl-CoA O-methyltransferase (CoMT) and cinnamyl alcohol dehydrogenase (CAD) showed higher expression in It than Ib. A total of 7,067 and 9,650 unique microsatellite markers, 1,037,396 and 495,931 single nucleotide polymorphisms (SNPs) and 103,439 and 69,194 InDels in Ib and It, respectively, were also identified from this study.

Conclusion: The detection of genes involved in the biosynthesis of RGL family proteins, the transcription factor RKD, and genes encoding a K efflux antiporter (KEA5) and the ERECTA protein kinase only in I. batatas indicate that these genes may have important functions in SR formation in sweetpotato. Potential molecular markers (SNPs, simple sequence repeats and InDels) and sequences identified in this study may represent a valuable resource for sweetpotato gene annotation and may serve as important tools for improving SR formation in sweetpotato through breeding.
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http://dx.doi.org/10.1186/s12870-016-0950-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5234144PMC
January 2017

Comparative transcriptome profiling of upland (VS16) and lowland (AP13) ecotypes of switchgrass.

Plant Cell Rep 2017 Jan 3;36(1):129-150. Epub 2016 Nov 3.

Molecular Genetics and Epigenomics Laboratory, College of Agriculture and Related Sciences, Delaware State University, Dover, DE, USA.

Key Message: Transcriptomes of two switchgrass genotypes representing the upland and lowland ecotypes will be key tools in switchgrass genome annotation and biotic and abiotic stress functional genomics. Switchgrass (Panicum virgatum L.) is an important bioenergy feedstock for cellulosic ethanol production. We report genome-wide transcriptome profiling of two contrasting tetraploid switchgrass genotypes, VS16 and AP13, representing the upland and lowland ecotypes, respectively. A total of 268 million Illumina short reads (50 nt) were generated, of which, 133 million were obtained in AP13 and the rest 135 million in VS16. More than 90% of these reads were mapped to the switchgrass reference genome (V1.1). We identified 6619 and 5369 differentially expressed genes in VS16 and AP13, respectively. Gene ontology and KEGG pathway analysis identified key genes that regulate important pathways including C4 photosynthesis, photorespiration and phenylpropanoid metabolism. A series of genes (33) involved in photosynthetic pathway were up-regulated in AP13 but only two genes showed higher expression in VS16. We identified three dicarboxylate transporter homologs that were highly expressed in AP13. Additionally, genes that mediate drought, heat, and salinity tolerance were also identified. Vesicular transport proteins, syntaxin and signal recognition particles were seen to be up-regulated in VS16. Analyses of selected genes involved in biosynthesis of secondary metabolites, plant-pathogen interaction, membrane transporters, heat, drought and salinity stress responses confirmed significant variation in the relative expression reflected in RNA-Seq data between VS16 and AP13 genotypes. The phenylpropanoid pathway genes identified here are potential targets for biofuel conversion.
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http://dx.doi.org/10.1007/s00299-016-2065-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5206262PMC
January 2017

The impact of orally administered phages on host immune response and surrounding microbial communities.

Bacteriophage 2016 Jul-Sep;6(3):e1211066. Epub 2016 Jul 13.

Department of Animal Sciences, Purdue University , West Lafayette, IN, USA.

Numerous studies have shown the efficacy of phage therapy in reducing foodborne pathogen carriage in food animals. Fewer studies have focused on host reactions, especially in terms of phage-mediated acute immune responses and effects on the gut microbiome. Here we administered O157:H7 phages in low (single dose of 10 PFU) or high (single dose of 10 PFU) quantities to mice. While there were time points at which cytokine levels in different treatment groups differed from one another, all cytokine levels remained within normal ranges for mice regardless of treatment. Similarly, the patterns of these differences were not dose related, indicating that phage treatment did not result in a strong acute immune response as measured here. In separate experiments, 3-week-old pigs received a diet containing an in-feed antibiotic or daily phage treatment. After two weeks, microbial DNA of ileal, cecal, and fecal contents was characterized using 16S rRNA sequencing. There were no statistical differences in performance among the different groups. Compared to control pigs (no antibiotic, no phage), antibiotic treatment significantly altered ileal microbiome composition (P < 0.05), with being most affected (antibiotic treated: 22%; control: 76%; FDR = 0.0572). No significant differences were observed in cecal and fecal microbiome composition between antibiotic-treated and control pigs, and there were no differences in gut microbiome composition between phage treated and control pigs in any intestinal compartment. Significant abundance differences were observed at the OTU level, with OTUs belonging to genera such as and being over- or under-represented in either antibiotic or phage treated groups compared to control pigs. Determining whether these changes are deleterious to host, however, requires further study.
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http://dx.doi.org/10.1080/21597081.2016.1211066DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5056770PMC
July 2016

Genomic insights into the Ixodes scapularis tick vector of Lyme disease.

Nat Commun 2016 Feb 9;7:10507. Epub 2016 Feb 9.

Department of Medicine, Division of Infectious Diseases, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA.

Ticks transmit more pathogens to humans and animals than any other arthropod. We describe the 2.1 Gbp nuclear genome of the tick, Ixodes scapularis (Say), which vectors pathogens that cause Lyme disease, human granulocytic anaplasmosis, babesiosis and other diseases. The large genome reflects accumulation of repetitive DNA, new lineages of retro-transposons, and gene architecture patterns resembling ancient metazoans rather than pancrustaceans. Annotation of scaffolds representing ∼57% of the genome, reveals 20,486 protein-coding genes and expansions of gene families associated with tick-host interactions. We report insights from genome analyses into parasitic processes unique to ticks, including host 'questing', prolonged feeding, cuticle synthesis, blood meal concentration, novel methods of haemoglobin digestion, haem detoxification, vitellogenesis and prolonged off-host survival. We identify proteins associated with the agent of human granulocytic anaplasmosis, an emerging disease, and the encephalitis-causing Langat virus, and a population structure correlated to life-history traits and transmission of the Lyme disease agent.
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http://dx.doi.org/10.1038/ncomms10507DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4748124PMC
February 2016

Genome-Wide Profiling of Histone Modifications (H3K9me2 and H4K12ac) and Gene Expression in Rust (Uromyces appendiculatus) Inoculated Common Bean (Phaseolus vulgaris L.).

PLoS One 2015 13;10(7):e0132176. Epub 2015 Jul 13.

Sequencing and Genotyping Center, Delaware Biotechnology Institute, Newark, Delaware, United States of America.

Histone modifications such as methylation and acetylation play a significant role in controlling gene expression in unstressed and stressed plants. Genome-wide analysis of such stress-responsive modifications and genes in non-model crops is limited. We report the genome-wide profiling of histone methylation (H3K9me2) and acetylation (H4K12ac) in common bean (Phaseolus vulgaris L.) under rust (Uromyces appendiculatus) stress using two high-throughput approaches, chromatin immunoprecipitation sequencing (ChIP-Seq) and RNA sequencing (RNA-Seq). ChIP-Seq analysis revealed 1,235 and 556 histone methylation and acetylation responsive genes from common bean leaves treated with the rust pathogen at 0, 12 and 84 hour-after-inoculation (hai), while RNA-Seq analysis identified 145 and 1,763 genes differentially expressed between mock-inoculated and inoculated plants. The combined ChIP-Seq and RNA-Seq analyses identified some key defense responsive genes (calmodulin, cytochrome p450, chitinase, DNA Pol II, and LRR) and transcription factors (WRKY, bZIP, MYB, HSFB3, GRAS, NAC, and NMRA) in bean-rust interaction. Differential methylation and acetylation affected a large proportion of stress-responsive genes including resistant (R) proteins, detoxifying enzymes, and genes involved in ion flux and cell death. The genes identified were functionally classified using Gene Ontology (GO) and EuKaryotic Orthologous Groups (KOGs). The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis identified a putative pathway with ten key genes involved in plant-pathogen interactions. This first report of an integrated analysis of histone modifications and gene expression involved in the bean-rust interaction as reported here provides a comprehensive resource for other epigenomic regulation studies in non-model species under stress.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0132176PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4500563PMC
April 2016

Metatranscriptomic profiles of Eastern subterranean termites, Reticulitermes flavipes (Kollar) fed on second generation feedstocks.

BMC Genomics 2015 Apr 22;16:332. Epub 2015 Apr 22.

Department of Entomology, Purdue University, West Lafayette, 47907-2089, Indiana.

Background: Second generation lignocellulosic feedstocks are being considered as an alternative to first generation biofuels that are derived from grain starches and sugars. However, the current pre-treatment methods for second generation biofuel production are inefficient and expensive due to the recalcitrant nature of lignocellulose. In this study, we used the lower termite Reticulitermes flavipes (Kollar), as a model to identify potential pretreatment genes/enzymes specifically adapted for use against agricultural feedstocks.

Results: Metatranscriptomic profiling was performed on worker termite guts after feeding on corn stover (CS), soybean residue (SR), or 98% pure cellulose (paper) to identify (i) microbial community, (ii) pathway level and (iii) gene-level responses. Microbial community profiles after CS and SR feeding were different from the paper feeding profile, and protist symbiont abundance decreased significantly in termites feeding on SR and CS relative to paper. Functional profiles after CS feeding were similar to paper and SR; whereas paper and SR showed different profiles. Amino acid and carbohydrate metabolism pathways were downregulated in termites feeding on SR relative to paper and CS. Gene expression analyses showed more significant down regulation of genes after SR feeding relative to paper and CS. Stereotypical lignocellulase genes/enzymes were not differentially expressed, but rather were among the most abundant/constitutively-expressed genes.

Conclusions: These results suggest that the effect of CS and SR feeding on termite gut lignocellulase composition is minimal and thus, the most abundantly expressed enzymes appear to encode the best candidate catalysts for use in saccharification of these and related second-generation feedstocks. Further, based on these findings we hypothesize that the most abundantly expressed lignocellulases, rather than those that are differentially expressed have the best potential as pretreatment enzymes for CS and SR feedstocks.
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http://dx.doi.org/10.1186/s12864-015-1502-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4411656PMC
April 2015

Transcriptomic and proteomic dynamics in the metabolism of a diazotrophic cyanobacterium, Cyanothece sp. PCC 7822 during a diurnal light-dark cycle.

BMC Genomics 2014 Dec 29;15:1185. Epub 2014 Dec 29.

Department of Biological Sciences, Purdue University, West Lafayette, IN, USA.

Background: Cyanothece sp. PCC 7822 is an excellent cyanobacterial model organism with great potential to be applied as a biocatalyst for the production of high value compounds. Like other unicellular diazotrophic cyanobacterial species, it has a tightly regulated metabolism synchronized to the light-dark cycle. Utilizing transcriptomic and proteomic methods, we quantified the relationships between transcription and translation underlying central and secondary metabolism in response to nitrogen free, 12 hour light and 12 hour dark conditions.

Results: By combining mass-spectrometry based proteomics and RNA-sequencing transcriptomics, we quantitatively measured a total of 6766 mRNAs and 1322 proteins at four time points across a 24 hour light-dark cycle. Photosynthesis, nitrogen fixation, and carbon storage relevant genes were expressed during the preceding light or dark period, concurrent with measured nitrogenase activity in the late light period. We describe many instances of disparity in peak mRNA and protein abundances, and strong correlation of light dependent expression of both antisense and CRISPR-related gene expression. The proteins for nitrogenase and the pentose phosphate pathway were highest in the dark, whereas those for glycolysis and the TCA cycle were more prominent in the light. Interestingly, one copy of the psbA gene encoding the photosystem II (PSII) reaction center protein D1 (psbA4) was highly upregulated only in the dark. This protein likely cannot catalyze O2 evolution and so may be used by the cell to keep PSII intact during N2 fixation. The CRISPR elements were found exclusively at the ends of the large plasmid and we speculate that their presence is crucial to the maintenance of this plasmid.

Conclusions: This investigation of parallel transcriptional and translational activity within Cyanothece sp. PCC 7822 provided quantitative information on expression levels of metabolic pathways relevant to engineering efforts. The identification of expression patterns for both mRNA and protein affords a basis for improving biofuel production in this strain and for further genetic manipulations. Expression analysis of the genes encoded on the 6 plasmids provided insight into the possible acquisition and maintenance of some of these extra-chromosomal elements.
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http://dx.doi.org/10.1186/1471-2164-15-1185DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4320622PMC
December 2014

Draft Genome Sequence of Acetobacter aceti Strain 1023, a Vinegar Factory Isolate.

Genome Announc 2014 Jun 5;2(3). Epub 2014 Jun 5.

Department of Biochemistry, Purdue University, West Lafayette, Indiana, USA

The genome sequence of Acetobacter aceti 1023, an acetic acid bacterium adapted to traditional vinegar fermentation, comprises 3.0 Mb (chromosome plus plasmids). A. aceti 1023 is closely related to the cocoa fermenter Acetobacter pasteurianus 386B but possesses many additional insertion sequence elements.
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http://dx.doi.org/10.1128/genomeA.00550-14DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4047455PMC
June 2014

MED18 interaction with distinct transcription factors regulates multiple plant functions.

Nat Commun 2014 ;5:3064

Department of Botany and Plant Pathology, Purdue University, 915 W State Street, West Lafayette, Indiana 47907, USA.

Mediator is an evolutionarily conserved transcriptional regulatory complex. Mechanisms of Mediator function are poorly understood. Here we show that Arabidopsis MED18 is a multifunctional protein regulating plant immunity, flowering time and responses to hormones through interactions with distinct transcription factors. MED18 interacts with YIN YANG1 to suppress disease susceptibility genes glutaredoxins GRX480, GRXS13 and thioredoxin TRX-h5. Consequently, yy1 and med18 mutants exhibit deregulated expression of these genes and enhanced susceptibility to fungal infection. In addition, MED18 interacts with ABA INSENSITIVE 4 and SUPPRESSOR OF FRIGIDA4 to regulate abscisic acid responses and flowering time, respectively. MED18 associates with the promoter, coding and terminator regions of target genes suggesting its function in transcription initiation, elongation and termination. Notably, RNA polymerase II occupancy and histone H3 lysine tri-methylation of target genes are affected in the med18 mutant, reinforcing MED18 function in different mechanisms of transcriptional control. Overall, MED18 conveys distinct cues to engender transcription underpinning plant responses.
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http://dx.doi.org/10.1038/ncomms4064DOI Listing
November 2015