Powdery mildews are fungal plant pathogens that infect a variety of agronomic and ornamental species, as well as the model plant Arabidopsis thaliana. Powdery mildews (PMs) establish specialized active feeding sites in the upper cell layer (epidermis) of the plant leaf through which they acquire all their nutrients. They require living plant tissue for their growth and reproduction and dramatically modulate leaf function and metabolism at the site of infection. Using lasers to specifically isolate only those cells at the site of PM infection, the investigators identified novel plant regulators and processes specifically altered by the sustained growth and reproduction of the PM Golovinomyces orontii on A. thaliana. Sixty-seven regulators were identified with subsets of these playing known or inferred roles in photosynthesis, cold/dehydration responses, plant defense, hormone signaling, and the cell cycle. The investigators will employ genetic, molecular, biochemical, and cytological approaches to characterize and classify these regulators based on their impact on PM growth and reproduction and the above processes. Furthermore, two of these processes will be explored in more detail using the above approaches. For example, using microscopic analysis, the investigators determined that the cell cycle is altered at the site of PM infection. Specifically, the number of copies of chromosomal DNA is dramatically enhanced in the cells underlying the infected epidermal cell. Furthermore, this increased copy number is required to maintain the full growth and reproduction of the fungus. The investigators will further define the factors responsible for this fungal-induced increase in chromosomal DNA and its role in the sustained growth and reproduction of the PM on Arabidopsis. Not only will this research identify targets for translational research in economically important plants impacted by PMs, but identified genes and processes may also impact other microbes that require living plant tissue and/or establish highly localized feeding sites. In addition, this highly localized, PM-inducible system should allow the investigators to uncover regulatory mechanisms governing fundamental processes, such as the cell cycle, that are challenging to explore using traditional approaches. Two postdoctoral scholars and four undergraduates, including students underrepresented in the sciences, will be trained in this interdisciplinary project. Outreach to students of local public elementary schools will enhance scientific literacy and inquiry using plants and school gardening programs as accessible entry points.
