Light-regulated development in Phytophthora: niche-specific diversification and evolution of the cryptochrome/photolyase superfamily

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Many organisms regulate their growth using environmental signals such as light, humidity, and chemicals. One biological process that is responsive to such cues in microbes is sporulation. This produces spores, which are used for transport to new geographic areas or to survive unfavorable conditions. Many pathogenic microbes also use spores to infect their hosts. This project will examine the role of environmental signals such as light on sporulation, with a focus on a large and economically important group of plant pathogens known as oomycetes. Some of these species make spores upon exposure to light, but light represses spore formation in other species. This project will test the hypothesis that sporulation is regulated by interactions between a specific type of photoreceptor protein and other components of the cell's regulatory machinery, such as those that activate or repress the activity of genes. The project will also explain at a molecular level why different species respond divergently to light. The research also has the potential for a practical return, since knowing what regulates sporulation can lead to the development of inhibitors of sporulation that will protect crops from disease. The project integrates research with education and outreach in communities with high minority demographics.In Phytophthora, a genus of plant pathogenic oomycetes, light stimulates sporulation by root pathogens but represses sporulation by foliar pathogens. This ensures that spores of root-infecting species appear above the soil line so that they can spread to new hosts, and that spores of foliar pathogens appear at night to avoid desiccation or UV damage. The goal of the research is to learn how these divergent responses to light evolved, using the root pathogen P. capsici and the foliar pathogen P. infestans as models. One objective is to use RNA-seq to characterize the effects of light on gene expression in the two species, and identify functional elements within light-induced promoters. A second objective is to study the role of cryptochromes on sporulation. These photoreceptor proteins are distributed widely in prokaryotes and eukaryotes, and have been shown to regulate growth, development, and metabolism. Their function in P. capsici and P. infestans will be examined using gene silencing, overexpression, heterologous expression, and protein-protein interaction studies. Having divergent responses to light within a single genus presents a unique opportunity for studying the evolution of an important developmental process. Graduate and undergraduate students will participate in the research, which will be integrated with programs for increasing student success and interest in STEM fields.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.