Publications by authors named "Jacob Shreve"

19 Publications

  • Page 1 of 1

Genome Sequence of the Virulent Model Herpes Simplex Virus 1 Strain McKrae Demonstrates the Presence of at Least Two Widely Used Variant Strains.

Microbiol Resour Announc 2021 Mar 25;10(12). Epub 2021 Mar 25.

Department of Biology, Pennsylvania State University, University Park, Pennsylvania, USA

Herpes simplex virus 1 (HSV-1) strain McKrae was isolated in 1965 and has been utilized by many laboratories. Three HSV-1 strain McKrae stocks have been sequenced previously, revealing discrepancies in key genes. We sequenced the genome of HSV-1 strain McKrae from the laboratory of James M. Hill to better understand the genetic differences between isolates.
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http://dx.doi.org/10.1128/MRA.01146-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7996463PMC
March 2021

The Evolving Landscape of Myelodysplastic Syndrome Prognostication.

Clin Hematol Int 2020 Jun 19;2(2):43-48. Epub 2020 Apr 19.

Department of Hematology and Medical Oncology, Taussig Cancer Center, Cleveland Clinic, 9500 Euclid Ave., Cleveland, OH, USA.

Myelodysplastic syndromes (MDSs) are potentially devastating monoclonal deviations of hematopoiesis that lead to bone marrow dysplasia and variable cytopenias. Predicting severity of disease progression and likelihood to undergo acute myeloid leukemia transformation is the basis of treatment strategy. Some patients belong to a low-risk cohort best managed with conservative supportive care, whereas others are included in a high-risk cohort that requires decisive therapy with hematopoietic cell transplantation or hypomethylating agent administration. Risk scoring systems for MDS prognostication were traditionally based on karyotype characteristics and clinical factors readily available from chart review, and validation was typically conducted on de novo MDS patients. However, retrospective analysis found a large subset of patients incorrectly risk-stratified. In this review, the most commonly used scoring systems are evaluated, and pitfalls therein are identified. Emerging technologies such as personal genomics and machine learning are then explored for efficacy in MDS risk modeling. Barriers to clinical adoption of artificial intelligence-derived models are discussed, with focus on approaches meant to increase model interpretability and clinical relevance. Finally, a guiding set of recommendations is proposed for best designing an accurate and universally applicable prognostic model for MDS, which is supported by more than 20 years of observation of traditional scoring system performance, as well as modern efforts in creating hybrid genomic-clinical scoring systems.
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http://dx.doi.org/10.2991/chi.d.200408.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7462414PMC
June 2020

Novel Prognostic Models for Myelodysplastic Syndromes.

Hematol Oncol Clin North Am 2020 04 5;34(2):369-378. Epub 2019 Dec 5.

Department of Hematology and Medical Oncology, Cleveland Clinic, Center for Clinical Artificial Intelligence, Lerner College of Medicine, Case Western Reserve University, Taussig Cancer Institute, Desk R35, 9500 Euclid Avenue, Cleveland, OH 44195, USA. Electronic address:

Myelodysplastic syndromes are disorders of clonal myelopoiesis having a range of clinical manifestations, from benign and indolent to aggressive with very poor prognosis. Classifying the likely trajectory of disease within a patient largely guides therapeutic decision making and therefore survival. Traditional methods of risk-stratification systems rely on clinical features: simple blood tests, peripheral smears, bone marrow biopsies, and cytogenetics, but do not adequately predict disease severity for a substantial proportion of patients. This article reviews the state of stratification at use in the clinic, describes emerging systems that leverage large-scale genomic data, and summarizes efforts toward truly personalized prediction models.
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http://dx.doi.org/10.1016/j.hoc.2019.10.001DOI Listing
April 2020

Expression profiles of cell-wall related genes vary broadly between two common maize inbreds during stem development.

BMC Genomics 2019 Oct 29;20(1):785. Epub 2019 Oct 29.

Department of Botany & Plant Pathology, Purdue University, 915 West State Street, West Lafayette, IN, 47907, USA.

Background: The cellular machinery for cell wall synthesis and metabolism is encoded by members of large multi-gene families. Maize is both a genetic model for grass species and a potential source of lignocellulosic biomass from crop residues. Genetic improvement of maize for its utility as a bioenergy feedstock depends on identification of the specific gene family members expressed during secondary wall development in stems.

Results: High-throughput sequencing of transcripts expressed in developing rind tissues of stem internodes provided a comprehensive inventory of cell wall-related genes in maize (Zea mays, cultivar B73). Of 1239 of these genes, 854 were expressed among the internodes at ≥95 reads per 20 M, and 693 of them at ≥500 reads per 20 M. Grasses have cell wall compositions distinct from non-commelinid species; only one-quarter of maize cell wall-related genes expressed in stems were putatively orthologous with those of the eudicot Arabidopsis. Using a slope-metric algorithm, five distinct patterns for sub-sets of co-expressed genes were defined across a time course of stem development. For the subset of genes associated with secondary wall formation, fifteen sequence motifs were found in promoter regions. The same members of gene families were often expressed in two maize inbreds, B73 and Mo17, but levels of gene expression between them varied, with 30% of all genes exhibiting at least a 5-fold difference at any stage. Although presence-absence and copy-number variation might account for much of these differences, fold-changes of expression of a CADa and a FLA11 gene were attributed to polymorphisms in promoter response elements.

Conclusions: Large genetic variation in maize as a species precludes the extrapolation of cell wall-related gene expression networks even from one common inbred line to another. Elucidation of genotype-specific expression patterns and their regulatory controls will be needed for association panels of inbreds and landraces to fully exploit genetic variation in maize and other bioenergy grass species.
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http://dx.doi.org/10.1186/s12864-019-6117-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6819468PMC
October 2019

Modulation of nonessential amino acid biosynthetic pathways in virulent Hessian fly larvae (Mayetiola destructor), feeding on susceptible host wheat (Triticum aestivum).

J Insect Physiol 2018 Feb - Mar;105:54-63. Epub 2018 Jan 11.

Department of Agronomy, Purdue University, West Lafayette, IN 47907, United States; USDA-ARS Crop Production and Pest Control Research Unit, West Lafayette, IN 47907, United States.

Compatible interactions between wheat (Triticum aestivum), and its dipteran pest Hessian fly (Hf, Mayetiola destructor) result in successful establishment of larval feeding sites rendering the host plant susceptible. Virulent larvae employ an effector-based feeding strategy to reprogram the host physiology resulting in formation of a protein- and sugar-rich nutritive tissue beneficial to developing larvae. Previous studies documented increased levels of nonessential amino acids (NAA; that need not be received through insect diet) in the susceptible wheat in response to larval feeding, suggesting importance of plant-derived NAA in larval nutrition. Here, we investigated the modulation of genes from NAA biosynthetic pathways (NAABP) in virulent Hf larvae. Transcript profiling for 16 NAABP genes, annotated from the recently assembled Hf genome, was carried out in the feeding first-, and second-instars and compared with that of the first-instar neonate (newly hatched, migrating, assumed to be non-feeding) larvae. While Tyr, Gln, Glu, and Pro NAABP genes transcript abundance declined in the feeding instars as compared to the neonates, those for Ala, and Ser increased in the feeding larval instars, despite higher levels of these NAA in the susceptible host plant. Asp, Asn, Gly and Cys NAABP genes exhibited variable expression profiles in the feeding first- and second-instars. Our results indicate that while Hf larvae utilize the plant-derived NAA, de novo synthesis of several NAA may be necessary to: (i) provide larvae with the requisite amount for sustaining growth before nutritive tissue formation and, (ii) overcome any inadequate amounts in the host plant, post-nutritive tissue formation.
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http://dx.doi.org/10.1016/j.jinsphys.2018.01.001DOI Listing
September 2019

The value of cold storage whole blood platelets in trauma resuscitation is like real estate: a function of 'location, location, location'.

Br J Haematol 2017 12 22;179(5):699-702. Epub 2017 Nov 22.

Department of Surgery, Memorial Hospital of South Bend, South Bend, IN, USA.

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http://dx.doi.org/10.1111/bjh.14998DOI Listing
December 2017

Fibrinolysis in Trauma: "Myth," "Reality," or "Something in Between".

Semin Thromb Hemost 2017 Mar 20;43(2):200-212. Epub 2017 Feb 20.

W. M. Keck Center for Transgene Research, University of Notre Dame, Notre Dame, Indiana.

The emphasis on fibrinolysis as an important contributor to trauma-induced coagulopathy (TIC) has led to a debate regarding the relative clinical significance of fibrinolysis in the setting of trauma. The debate has centered on two camps. The one camp defines fibrinolysis in trauma by standard coagulation tests as well as fibrin split products, D-dimers, and plasmin/antiplasmin levels. This camp favors a more liberal use of tranexamic acid and attributes more significance to hyperfibrinolysis in TIC. The other camp favors a definition of fibrinolysis based on the viscoelastic tests (VET), rotational thromboelastometry (ROTEM), and thromboelastography (TEG). These whole blood assays define hyperfibrinolysis at a higher threshold than plasma-based tests. Therefore, this VET camp reserves antifibrinolytic treatment for patients who demonstrate severe coagulopathy associated with hyperfibrinolysis. This bimodal attribution of the clinical relevance of fibrinolysis in trauma suggests that there may be an underlying "Myth" of the concept of TIC that was historically defined by plasma-based tests and a future "Reality" of the concept of TIC that is grounded on an understanding of TIC based on a VET-defined "fibrinolytic spectrum" of TIC. This narrative review explores this "Myth" and "Reality" of fibrinolysis in TIC and proposes a direction that will allow a "Future" interpretation of TIC that incorporates both the past "Myth" and present "Reality" of fibrinolysis TIC.
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http://dx.doi.org/10.1055/s-0036-1597900DOI Listing
March 2017

Tranexamic Acid for Trauma Resuscitation in the United States of America.

Semin Thromb Hemost 2017 Mar 1;43(2):213-223. Epub 2016 Dec 1.

W.M. Keck Center for Transgene Research, Notre Dame, Indiana.

The utilization of tranexamic acid (TXA) for the management of bleeding trauma patients has been a subject of much debate on both sides of the Atlantic and in Australia. As a result of the large randomized controlled study called the , there was an initial enthusiasm for the use of TXA to treat bleeding patients. However, the adoption of TXA in the United States was delayed by concerns of "knowledge and evidence gaps" of the CRASH-2 study and because of a lack of mechanistic rationale that would explain the survival benefit noted in the study. Subsequent nonrandomized controlled trials questioned the liberal use of TXA in trauma patients. This narrative review explores the historical as well as clinical and theoretical grounds for the more measured use of TXA in the United States and proposes a clinical and point-of-care guided utilization of TXA, blood components, and adjunctive hemostatic agents in bleeding trauma patients.
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http://dx.doi.org/10.1055/s-0036-1586226DOI Listing
March 2017

DNA from Dust: Comparative Genomics of Large DNA Viruses in Field Surveillance Samples.

mSphere 2016 Sep-Oct;1(5). Epub 2016 Oct 5.

Department of Biochemistry and Molecular Biology, Center for Infectious Disease Dynamics, and the Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, Pennsylvania, USA.

The intensification of the poultry industry over the last 60 years facilitated the evolution of increased virulence and vaccine breaks in Marek's disease virus (MDV-1). Full-genome sequences are essential for understanding why and how this evolution occurred, but what is known about genome-wide variation in MDV comes from laboratory culture. To rectify this, we developed methods for obtaining high-quality genome sequences directly from field samples without the need for sequence-based enrichment strategies prior to sequencing. We applied this to the first characterization of MDV-1 genomes from the field, without prior culture. These viruses were collected from vaccinated hosts that acquired naturally circulating field strains of MDV-1, in the absence of a disease outbreak. This reflects the current issue afflicting the poultry industry, where virulent field strains continue to circulate despite vaccination and can remain undetected due to the lack of overt disease symptoms. We found that viral genomes from adjacent field sites had high levels of overall DNA identity, and despite strong evidence of purifying selection, had coding variations in proteins associated with virulence and manipulation of host immunity. Our methods empower ecological field surveillance, make it possible to determine the basis of viral virulence and vaccine breaks, and can be used to obtain full genomes from clinical samples of other large DNA viruses, known and unknown. Despite both clinical and laboratory data that show increased virulence in field isolates of MDV-1 over the last half century, we do not yet understand the genetic basis of its pathogenicity. Our knowledge of genome-wide variation between strains of this virus comes exclusively from isolates that have been cultured in the laboratory. MDV-1 isolates tend to lose virulence during repeated cycles of replication in the laboratory, raising concerns about the ability of cultured isolates to accurately reflect virus in the field. The ability to directly sequence and compare field isolates of this virus is critical to understanding the genetic basis of rising virulence in the wild. Our approaches remove the prior requirement for cell culture and allow direct measurement of viral genomic variation within and between hosts, over time, and during adaptation to changing conditions.
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http://dx.doi.org/10.1128/mSphere.00132-16DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5064450PMC
October 2016

Viral forensic genomics reveals the relatedness of classic herpes simplex virus strains KOS, KOS63, and KOS79.

Virology 2016 May 21;492:179-86. Epub 2016 Mar 21.

Department of Biochemistry and Molecular Biology, and the Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802, USA. Electronic address:

Herpes simplex virus 1 (HSV-1) is a widespread global pathogen, of which the strain KOS is one of the most extensively studied. Previous sequence studies revealed that KOS does not cluster with other strains of North American geographic origin, but instead clustered with Asian strains. We sequenced a historical isolate of the original KOS strain, called KOS63, along with a separately isolated strain attributed to the same source individual, termed KOS79. Genomic analyses revealed that KOS63 closely resembled other recently sequenced isolates of KOS and was of Asian origin, but that KOS79 was a genetically unrelated strain that clustered in genetic distance analyses with HSV-1 strains of North American/European origin. These data suggest that the human source of KOS63 and KOS79 could have been infected with two genetically unrelated strains of disparate geographic origins. A PCR RFLP test was developed for rapid identification of these strains.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5056906PMC
http://dx.doi.org/10.1016/j.virol.2016.02.013DOI Listing
May 2016

Identification of a plastidial phenylalanine exporter that influences flux distribution through the phenylalanine biosynthetic network.

Nat Commun 2015 Sep 10;6:8142. Epub 2015 Sep 10.

Department of Biochemistry, Purdue University, 175 South University Street, West Lafayette, Indiana 47907-2063, USA.

In addition to proteins, L-phenylalanine is a versatile precursor for thousands of plant metabolites. Production of phenylalanine-derived compounds is a complex multi-compartmental process using phenylalanine synthesized predominantly in plastids as precursor. The transporter(s) exporting phenylalanine from plastids, however, remains unknown. Here, a gene encoding a Petunia hybrida plastidial cationic amino-acid transporter (PhpCAT) functioning in plastidial phenylalanine export is identified based on homology to an Escherichia coli phenylalanine transporter and co-expression with phenylalanine metabolic genes. Radiolabel transport assays show that PhpCAT exports all three aromatic amino acids. PhpCAT downregulation and overexpression result in decreased and increased levels, respectively, of phenylalanine-derived volatiles, as well as phenylalanine, tyrosine and their biosynthetic intermediates. Metabolic flux analysis reveals that flux through the plastidial phenylalanine biosynthetic pathway is reduced in PhpCAT RNAi lines, suggesting that the rate of phenylalanine export from plastids contributes to regulating flux through the aromatic amino-acid network.
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http://dx.doi.org/10.1038/ncomms9142DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4647861PMC
September 2015

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

Rapid genome assembly and comparison decode intrastrain variation in human alphaherpesviruses.

mBio 2015 Mar 31;6(2). Epub 2015 Mar 31.

Unlabelled: Herpes simplex virus (HSV) is a widespread pathogen that causes epithelial lesions with recurrent disease that manifests over a lifetime. The lifelong aspect of infection results from latent viral infection of neurons, a reservoir from which the virus reactivates periodically. Recent work has demonstrated the breadth of genetic variation in globally distributed HSV strains. However, the amount of variation or capacity for mutation within one strain has not been well studied. Here we developed and applied a streamlined new approach for assembly and comparison of large DNA viral genomes such as HSV-1. This viral genome assembly (VirGA) workflow incorporates a combination of de novo assembly, alignment, and annotation strategies to automate the generation of draft genomes for large viruses. We applied this approach to quantify the amount of variation between clonal derivatives of a common parental virus stock. In addition, we examined the genetic basis for syncytial plaque phenotypes displayed by a subset of these strains. In each of the syncytial strains, we found an identical DNA change, affecting one residue in the gB (UL27) fusion protein. Since these identical mutations could have appeared after extensive in vitro passaging, we applied the VirGA sequencing and comparison approach to two clinical HSV-1 strains isolated from the same patient. One of these strains was syncytial upon first culturing; its sequence revealed the same gB mutation. These data provide insight into the extent and origin of genome-wide intrastrain HSV-1 variation and present useful methods for expansion to in vivo patient infection studies.

Importance: Herpes simplex virus (HSV) infects more than 70% of adults worldwide, causing epithelial lesions and recurrent disease that manifests over a lifetime. Prior work has demonstrated that HSV strains vary from country to country and between individuals. However, the amount of variation within one strain has not been well studied. To address this, we developed a new approach for viral genome assembly (VirGA) and analysis. We used this approach to quantify the amount of variation between sister clones of a common parental virus stock and to determine the basis of a unique fusion phenotype displayed by several variants. These data revealed that while sister clones of one HSV stock are more than 98% identical, these variants harbor enough genetic differences to change their observed characteristics. Comparative genomics approaches will allow us to explore the impacts of viral inter- and intrastrain diversity on drug and vaccine efficacy.
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http://dx.doi.org/10.1128/mBio.02213-14DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4453532PMC
March 2015

Coordination of MicroRNAs, PhasiRNAs, and NB-LRR Genes in Response to a Plant Pathogen: Insights from Analyses of a Set of Soybean Rps Gene Near-Isogenic Lines.

Plant Genome 2015 Mar;8(1):eplantgenome2014.09.0044

Dep. of Agronomy, Purdue Univ., West Lafayette, IN, 47907.

Disease-related genes, particularly the nucleotide binding site (NB)-leucine-rich repeat (LRR) class of R plant genes can be triggered by microRNAs (miRNAs) to generate phased small interfering RNAs (phasiRNAs), which could reduce the transcript levels of their targets. However, how global changes in NB-LRR transcript levels coordinate with changes in miRNA and phasiRNA levels in defense responses remains largely unknown. Here, we investigated changes in the relative abundance of small RNAs (sRNAs), with a focus on miRNAs and phasiRNAs and their potential targets in response to the pathogen Phytophthora sojae in the susceptible soybean [Glycine max (L.) Merr.] 'Williams' and nine resistant near-isogenic lines (NILs), each carrying a unique resistance to P. sojae (Rps) gene. In total, 369 distinct miRNAs, including 78 new ones, were identified in the 10 soybean lines. The majority of miRNAs were downregulated by the pathogen. Of the 525 NB-LRR genes found in the soybean reference genome, 257 were predicted to be the targets of eight abundant miRNA families and 126 (dubbed phasi-NB-LRRs or pNLs) were predicted to have produced phasiRNAs. Upregulation of 15 phasi-NB-LRRs was associated with downregulation of their corresponding phasiRNAs in the NILs; these phasiRNAs were predicted to regulate 75 additional NB-LRRs in trans. In addition, we identified putative 24-nucleotide (nt) phasiRNAs from transposons, possibly representing a novel general epigenetic mechanism for regulation of transposon activity under biotic stresses. Together, these observations suggest that miRNAs and phasiRNAs play an important role in response to plant pathogens through complex, multiple layers of post-transcriptional regulation.
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http://dx.doi.org/10.3835/plantgenome2014.09.0044DOI Listing
March 2015

A massive expansion of effector genes underlies gall-formation in the wheat pest Mayetiola destructor.

Curr Biol 2015 Mar 5;25(5):613-20. Epub 2015 Feb 5.

Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.

Gall-forming arthropods are highly specialized herbivores that, in combination with their hosts, produce extended phenotypes with unique morphologies [1]. Many are economically important, and others have improved our understanding of ecology and adaptive radiation [2]. However, the mechanisms that these arthropods use to induce plant galls are poorly understood. We sequenced the genome of the Hessian fly (Mayetiola destructor; Diptera: Cecidomyiidae), a plant parasitic gall midge and a pest of wheat (Triticum spp.), with the aim of identifying genic modifications that contribute to its plant-parasitic lifestyle. Among several adaptive modifications, we discovered an expansive reservoir of potential effector proteins. Nearly 5% of the 20,163 predicted gene models matched putative effector gene transcripts present in the M. destructor larval salivary gland. Another 466 putative effectors were discovered among the genes that have no sequence similarities in other organisms. The largest known arthropod gene family (family SSGP-71) was also discovered within the effector reservoir. SSGP-71 proteins lack sequence homologies to other proteins, but their structures resemble both ubiquitin E3 ligases in plants and E3-ligase-mimicking effectors in plant pathogenic bacteria. SSGP-71 proteins and wheat Skp proteins interact in vivo. Mutations in different SSGP-71 genes avoid the effector-triggered immunity that is directed by the wheat resistance genes H6 and H9. Results point to effectors as the agents responsible for arthropod-induced plant gall formation.
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http://dx.doi.org/10.1016/j.cub.2014.12.057DOI Listing
March 2015

Genome Sequence of the Anterograde-Spread-Defective Herpes Simplex Virus 1 Strain MacIntyre.

Genome Announc 2014 Nov 13;2(6). Epub 2014 Nov 13.

Department of Molecular Biology, the Princeton Neuroscience Institute, Princeton University, Princeton, New Jersey, USA.

We used paired-end Illumina deep sequencing and de novo assembly to determine the genome sequence of herpes simplex virus 1 (HSV-1) strain MacIntyre (aka McIntyre). The MacIntyre strain originated from the brain of a patient with lethal HSV encephalitis and has a unique limitation in its neuronal spread, moving solely in the retrograde direction.
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http://dx.doi.org/10.1128/genomeA.01161-14DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4241663PMC
November 2014

Genetic Determinants for Enzymatic Digestion of Lignocellulosic Biomass Are Independent of Those for Lignin Abundance in a Maize Recombinant Inbred Population.

Plant Physiol 2014 Aug 27;165(4):1475-1487. Epub 2014 Jun 27.

Departments of Biological Sciences (B.W.P., M.C.M., N.C.C.), Botany and Plant Pathology (C.K.D., M.A.H., J.F.K., N.C.C.), and Agronomy (N.C.B., C.F.W.), Laboratory of Renewable Resources Engineering and Agricultural and Biological Engineering (N.S.M.), and Bioinformatics Core (J.T.S., J.T.), Purdue University, West Lafayette, Indiana 47907;National Bioenergy Center, National Renewable Energy Laboratory, Golden, Colorado 80401 (R.W.S., M.F., A.Z., M.F.D., S.R.D., G.B.T.); andDepartment of Plant Biology, University of Minnesota, St. Paul, Minnesota 55108 (N.M.S.)

Biotechnological approaches to reduce or modify lignin in biomass crops are predicated on the assumption that it is the principal determinant of the recalcitrance of biomass to enzymatic digestion for biofuels production. We defined quantitative trait loci (QTL) in the Intermated B73 × Mo17 recombinant inbred maize (Zea mays) population using pyrolysis molecular-beam mass spectrometry to establish stem lignin content and an enzymatic hydrolysis assay to measure glucose and xylose yield. Among five multiyear QTL for lignin abundance, two for 4-vinylphenol abundance, and four for glucose and/or xylose yield, not a single QTL for aromatic abundance and sugar yield was shared. A genome-wide association study for lignin abundance and sugar yield of the 282-member maize association panel provided candidate genes in the 11 QTL of the B73 and Mo17 parents but showed that many other alleles impacting these traits exist among this broader pool of maize genetic diversity. B73 and Mo17 genotypes exhibited large differences in gene expression in developing stem tissues independent of allelic variation. Combining these complementary genetic approaches provides a narrowed list of candidate genes. A cluster of SCARECROW-LIKE9 and SCARECROW-LIKE14 transcription factor genes provides exceptionally strong candidate genes emerging from the genome-wide association study. In addition to these and genes associated with cell wall metabolism, candidates include several other transcription factors associated with vascularization and fiber formation and components of cellular signaling pathways. These results provide new insights and strategies beyond the modification of lignin to enhance yields of biofuels from genetically modified biomass.
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http://dx.doi.org/10.1104/pp.114.242446DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4119032PMC
August 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

A genome-wide survey of small interfering RNA and microRNA pathway genes in a galling insect.

J Insect Physiol 2013 Mar 8;59(3):367-76. Epub 2012 Dec 8.

Department of Entomology, Purdue University, West Lafayette, IN 47907, USA.

Deployment of resistance (R) genes is the most effective control for Hessian fly, Mayetiola destructor (Say); however, deployment of R genes results in an increased frequency of pest genotypes that display virulence to them. RNA interference (RNAi) is a useful reverse genetics tool for studying such insect virulence pathways, but requires a systemic phenotype, which is not found in all species. In an effort to correlate our observed weak RNAi phenotype in M. destructor with a genetic basis, we have aggregated and compared RNAi related genes across M. destructor, three other insect species, and the nematode Caenorhabditis elegans. We report here the annotation of the core genes in the small interfering RNA (siRNA) and microRNA (miRNA) pathways in M. destructor. While most of the miRNA pathway genes were highly conserved across the species studied, the siRNA pathway genes showed increased relative variability in comparison to the miRNA pathway. In particular, the Piwi/Argonaute/Zwille (PAZ) domain of Dicer-2 (DCR-2) had the least amount of sequence similarity of any domain among species surveyed, with a trend of increased conservation in those species with amenable systemic RNAi. A homolog of the systemic interference defective-1 (Sid-1) gene of C. elegans was also not annotated in the M. destructor genome. Indeed, it is of interest that a Sid-1 homolog has not been detected in any dipteran species to date. We hypothesize the sequence architecture of the PAZ domain in the M. destructor DCR-2 protein is related to reduced efficacy of this enzyme and this taken together with the lack of a Sid-1 homolog may account for the weak RNAi response observed to date in this species as well as other dipteran species.
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http://dx.doi.org/10.1016/j.jinsphys.2012.11.009DOI Listing
March 2013