This research explores the relationship between genotype and phenotype in the context of genetic networks. The investigator will use a combination of experimental and mathematical approaches to characterize the effects of genetic variation on the regulatory pathways that determine responses to nitrogen starvation in Saccharomyces cerevisiae (budding yeast). Yeast cells that are starved for nitrogen can undergo one of two mutually exclusive developmental processes - sporulation or pseudohyphal growth. The regulatory and signaling pathways that underlie these two responses are intertwined. This study will characterize the impact of genetic variation on these overlapping genetic pathways and explore how genetic polymorphism contributes to variable patterns of gene expression and ultimately to distinct sporulation and pseudohyphal growth phenotypes. The investigator will employ gene disruptions and phenotypic assays to validate a set of potential mutational targets that affect both phenotypes of interest. This set of validated gene targets will form a 'candidate network' for further study. DNA sequencing will be carried out to identify polymorphisms in the protein coding and regulatory sequences for genes in this candidate network. The functional consequences of these polymorphisms will be assessed using RT-PCR based assays to determine if the genetic differences identified confer allelic biases in gene expression. These data will be combined with biochemical, genetic, and genomic information from previous studies to build a mathematical model of the regulatory networks that will be used to explore mechanistic hypotheses relating gene expression variation to cellular phenotypes. This research will provide significant advances towards our understanding of the genetic basis of variation for complex traits by providing a detailed picture of genetic variation across a large genetic network. The experiments and modeling efforts to be carried out will provide insights into the functional consequences of this variation with respect to regulatory network function. Furthermore, this project will lead to the development of a novel experimental system for exploring important genetic phenomena such as pleiotropy and epistasis.
A key issue in biology is to understand how variation at the level of DNA relates to phenotypic variation (e.g. physiology, morphology, behavior). A thorough understanding of such relationships requires the study of mutational effects on single genes as well as investigations focused on networks of interacting genes and gene products. The research to be conducted under the auspices of this grant will contribute to a greater understanding of how genetic variation impacts gene networks and how the behavior of such networks leads to distinct cellular phenotypes. Using a combination of experimental and mathematical approaches the investigator will study the affects of genetic variation on signaling pathways and gene networks that determine how budding yeast (Saccharomyces cerevisiae) respond to a simple environmental cue (nitrogen starvation). Yeast is one of the best studied eukaryotic model systems as well as an important agricultural and industrial microorganism. A deeper understanding of genotype-phenotype relationships will advance yeast genetics and will help to pave the way for similar studies in agriculturally important animals and plants. The broader societal impacts of this research are to promote training and mentoring at the postdoctoral and undergraduate levels and to foster the development of scientists from underrepresented groups. The principal investigator is a member of a group under-represented in science.
