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KSRE Seminars
Plant Pathology Seminars
Department of Plant Pathology Special Seminars

Dr. Chris Toomajian
Kansas State University, Department of Plant Pathology
“Population Genomics: From A. thaliana to Gibberella zeae”
October 9, 2014
Central to the field of population genomics, studies of naturally occurring genetic variants that differ within populations or between species can determine the functional consequence of this variation and also can uncover the demographic and evolutionary history of populations. Population genomics analyses of plants help to reveal the genetic basis of agronomically important traits, while similar analyses in plant pathogens can be critical for developing effective methods for their control. Next Generation Sequencing technologies now simplify the large-scale recovery of genetic variants through genome sequencing, targeted genotyping, and gene expression (RNA-Seq) experiments.
My seminar will focus on three ongoing projects that demonstrate how I have leveraged genomics approaches learned from model systems like Arabidopsis to benefit plant pathogen research. One project examines gene expression variation in Arabidopsis with RNA-Seq. Understanding this variation provides a critical link that connects genotype to phenotype. By measuring transcriptome variation across different genotypes, we are mapping genetic variants that influence gene expression level and inferring the adaptive significance of these variants. The second project aims to determine the genetic basis of host-specificity and speciation comparing the closely related plant pathogens Fusarium fujikuroi and F. proliferatum. My lab has developed genotype by sequencing (GBS) markers for creating a genetic map from a cross between these two species, and has also generated draft genome sequences for comparative genomic analyses. Our third project employs GBS to investigate the population genomics of F. graminearum (formerly Gibberella zeae), the predominant causal agent of Fusarium head blight (FHB) in most of the world. We are genotyping hundreds of samples to describe patterns of variation across different spatial scales. Our specific aim is to test whether genomic footprints of selection support the hypothesis that genetic changes at an FHB-related mycotoxin locus have spread via natural selection.

Dr. Richard Todd
Kansas State University, Department of Plant Pathology
“Nitrogen metabolic gene regulation in a model fungus: transcription factors and molecular mechanisms”
Nutrient acquisition and metabolism are fundamental for organisms to grow, survive and flourish. In fungi, the genes for uptake and metabolism of nitrogen nutrients are regulated by transcription factors in response to nitrogen nutrient availability, allowing metabolic reconfiguration for adaptation to different nutritional environments. Metabolic reconfiguration is important for fungal pathogens as they invade the generally nitrogen-poor host environment. The fungus Aspergillus nidulans is a powerful genetic and genomic model for understanding the molecular mechanisms underlying nitrogen metabolic gene regulation. The expression levels for nitrogen metabolic genes are generally determined by the combined actions of a global GATA DNA-binding transcription factor, AreA, which is thought to activate most nitrogen utilization genes, and a pathway-specific transcription factor that regulates only a subset of genes whose products function within the same (or related) metabolic pathway(s). AreA activity is highly regulated by multiple mechanisms, including by interactions with several other transcription factors, and via regulated accumulation in the nucleus during nitrogen starvation. I will provide an overview of our current knowledge of nitrogen metabolic gene regulation in A. nidulans, focusing on advances my lab has made in understanding molecular mechanisms controlling AreA transcription factor action. These include: dissection of the AreA nuclear import and nuclear export mechanisms, identification of novel AreA regulators and new genome-wide AreA targets, and characterization of two GAL4-family transcription factors, TamA and the leucine biosynthesis regulator LeuB, which cooperate with AreA to regulate expression of NADP-glutamate dehydrogenase, a critical enzyme in nitrogen assimilation. TamA was thought for the last ~20 years to act as a co-activator of AreA, with its DNA-binding motif dispensable for known functions. We now show that TamA is the first fungal dual function transcription factor, which acts as a DNA-binding transcription factor or as a non-DNA-binding transcription co-activator depending on promoter context.

Dr. Martin C. Quincke, PhD
Head Wheat Breeder, INIA La Estanzuela
"Wheat Production in Uruguay and the Wheat Breeding
Program at INIA La Estanzuela"
Monday, July 28, 2014