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Rockville, MD, United States

Munkvold J.D.,Cornell University | Munkvold J.D.,Keygene Inc | Laudencia-Chingcuanco D.,U.S. Department of Agriculture | Sorrells M.E.,Cornell University
Genetics | Year: 2013

Quantitative phenotypic traits are influenced by genetic and environmental variables as well as the interaction between the two. Underlying genetic · environment interaction is the influence that the surrounding environment exerts on gene expression. Perturbation of gene expression by environmental factors manifests itself in alterations to gene co-expression networks and ultimately in phenotypic plasticity. Comparative gene co-expression networks have been used to uncover biological mechanisms that differentiate tissues or other biological factors. In this study, we have extended consensus and differential Weighted Gene Co-Expression Network Analysis to compare the influence of different growing environments on gene co-expression in the mature wheat (Triticum aestivum) embryo. This network approach was combined with mapping of individual gene expression QTL to examine the genetic control of environmentally static and variable gene expression. The approach is useful for gene expression experiments containing multiple environments and allowed for the identification of specific gene co-expression modules responsive to environmental factors. This procedure identified conserved coregulation of gene expression between environments related to basic developmental and cellular functions, including protein localization and catabolism, vesicle composition/trafficking, Golgi transport, and polysaccharide metabolism among others. Environmentally unique modules were found to contain genes with predicted functions in responding to abiotic and biotic environmental variables. These findings represent the first report using consensus and differential Weighted Gene Coexpression Network Analysis to characterize the influence of environment on coordinated transcriptional regulation. © 2013 by the Genetics Society of America. Source

DiLeo M.V.,Boyce Thompson Institute for Plant Research | DiLeo M.V.,Robert lley Center For Agriculture And Health | DiLeo M.V.,Keygene Inc | den Bakker M.,Boyce Thompson Institute for Plant Research | And 6 more authors.
Plant Genome | Year: 2014

While the greatest strength of systems biology may be to measure tens of thousands of variables across different genotypes, this simultaneously presents an enormous challenge to statistical analysis that cannot be completely solved with conventional approaches that identify and rank differences. Here we examine a diverse panel of conventional and transgenic, field-grown tomato fruits (Solanum lycopersicum L.) by liquid chromatography-mass spectrometry (LC-MS) metabolic fingerprinting. We used a progression of statistics to examine phenotypic variation observed. While clear trends were found by principal component analysis (PCA) related to genetic background and ripeness, it could not detect differences between transgenic genotypes and their nontransgenic parent variety. Partial least squares discriminant analysis (PLS-DA), a supervised method, identified 15 metabolic features of potential interest, but only five were significantly different between the transgenic lines and their nontransgenic parent. Weighted correlation network analysis (WGCNA) recognized relationships among these features and others, suggesting that a small suite of highly correlated compounds accumulated to significantly lower levels in the transgenic genotypes. We assert that metabolic fingerprinting with a series of statistical methods is an efficient and powerful approach to examine both large and small genetic effects on phenotypes of high value or interest. © Crop Science Society of America. Source

Zwick M.E.,Emory University | Zwick M.E.,Biological Defense Research Directorate | Joseph S.J.,Emory University | Didelot X.,University of Oxford | And 18 more authors.
Genome Research | Year: 2012

The key genes required for Bacillus anthracis to cause anthrax have been acquired recently by horizontal gene transfer. To understand the genetic background for the evolution of B. anthracis virulence, we obtained high-redundancy genome sequences of 45 strains of the Bacillus cereus sensu lato (s.l.) species that were chosen for their genetic diversity within the species based on the existing multilocus sequence typing scheme. From the resulting data, we called more than 324,000 new genes representing more than 12,333 new gene families for this group. The core genome size for the B. cereus s.l. group was ∼1750 genes, with another 2150 genes found in almost every genome constituting the extended core. There was a paucity of genes specific and conserved in any clade. We found no evidence of recent large-scale gene loss in B. anthracis or for unusual accumulation of nonsynonymous DNA substitutions in the chromosome; however, several B. cereus genomes isolated from soil and not previously associated with human disease were degraded to various degrees. Although B. anthracis has undergone an ecological shift within the species, its chromosome does not appear to be exceptional on a macroscopic scale compared with close relatives. Source

DiLeo M.V.,University of California at Davis | DiLeo M.V.,Keygene Inc | Bostock R.M.,University of California at Davis | Rizzo D.M.,University of California at Davis
PLoS ONE | Year: 2014

Phytophthora ramorum, an invasive pathogen and the causal agent of Sudden Oak Death, has become established in mixed-evergreen and redwood forests in coastal northern California. While oak and tanoak mortality is the most visible indication of P. ramorum's presence, epidemics are largely driven by the presence of bay laurel (Umbellularia californica), a reservoir host that supports both prolific sporulation in the winter wet season and survival during the summer dry season. In order to better understand how over-summer survival of the pathogen contributes to variability in the severity of annual epidemics, we monitored the viability of P. ramorum leaf infections over three years along with coincident microclimate. The proportion of symptomatic bay laurel leaves that contained viable infections decreased during the first summer dry season and remained low for the following two years, likely due to the absence of conducive wet season weather during the study period. Over-summer survival of P. ramorum was positively correlated with high percent canopy cover, less negative bay leaf water potential and few days exceeding 30°C but was not significantly different between mixed-evergreen and redwood forest ecosystems. Decreased summer survival of P. ramorum in exposed locations and during unusually hot summers likely contributes to the observed spatiotemporal heterogeneity of P. ramorum epidemics. © 2014 DiLeo et al. Source

Albrecht E.,Keygene Inc | Zhang D.,U.S. Department of Agriculture | Saftner R.A.,U.S. Department of Agriculture | Stommel J.R.,U.S. Department of Agriculture
Genetic Resources and Crop Evolution | Year: 2012

Capsicum baccatum is one of five domesticated pepper species which, despite its morphological and ecological variability, has been underexploited for germplasm improvement. Utilizing a broad spectrum of domesticated and wild C. baccatum germplasm, we utilize AFLP markers to describe the species' molecular diversity and population structure in the South American gene pool. Analysis of molecular variance (AMOVA) revealed greater genetic diversity in the wild form of C. baccatum (C. baccatum var. baccatum) than in the domesticated form of the species (C. baccatum var. pendulum). Both Bayesian and distance based clustering analysis, as well as principal coordinates analysis (PCA), concordantly demonstrated admixture/shared ancestry between wild and cultivated C. baccatum botanical varieties. Two principal genetic groups were identified in the domesticated C. baccatum accessions largely based on their geographic distribution in South America. One group was predominated by accessions from the western territories of the species' distribution (Peru, Colombia, Ecuador, Bolivia, Chile and northwestern Argentina) and the second by accessions from the eastern regions, Paraguay and eastern Argentina). The two genetic groups overlapped in the geographic location of present-day Bolivia. The grouping pattern suggested that C. baccatum was domesticated in multiple sites and that its evolution took two lineages followed by lineage differentiation. The wild accessions most closely related to the cultigens were found in the highlands of Peru and Bolivia, which support the early hypothesis that this region is one of the domestication sites of this species. A Bayesian assignment analysis demonstrated that Brazilian wild forms of C. baccatum were genetically distant to all other accessions and made little to no contribution to the domesticated genepool. Moreover, results of clustering analysis suggested that C. baccatum likely originated from present day Paraguay. Analysis of inter-specific relationships across selected Capsicum species supported independent lineages for the two crossability groups within Capsicum, the baccatum species-complex (including C. baccatum) and the annuum species-complex (including C. annuum, C. chinense and C. frutescens). However, the results did not support taxonomic distinction of C. baccatum var. umbilicatum from C. baccatum var. pendulum. The present study provides new insights into the domestication of C. baccatum. The results will be useful for identifying accessions for crop improvement and guiding the development of in situ and ex situ conservation programs. © 2011 Springer Science+Business Media B.V. (outside the USA). Source

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