Novel bZIP Transcription Factors and Redox Biology in the Oomycete Phytophthora Infestans

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Organisms must be able to protect their cells from damage caused by reactive oxygen species (ROS), which are chemicals that may arise as a byproduct of normal metabolism or stressful growth conditions such as starvation. High concentrations of ROS can damage biomolecules within cells, while lower levels may serve as signals for regulating the cell's machinery. The principal goal of this project is to study a novel mechanism that Phytophthora infestans may use to perceive and respond to ROS. P. infestans is a notorious plant pathogen and a member of the oomycetes, an economically important but under-studied group of microbes. Oomycetes produce a novel protein regulator of gene expression that contains the amino acid cysteine in its DNA-binding domain. ROS are hypothesized to alter the chemical form of the cysteine, altering the protein's effect on gene expression. Understanding this process may lead to new strategies for protecting crops from disease caused by oomycetes, as well as novel switches for engineering gene expression and increasing yields in industrial microbes or plants. The project will also contribute to the mentorship and training of students in STEM fields by integrating research with education and outreach in communities with high minority demographics.Prior studies of bZIP transcription factors from model plants and animals identified residues in their DNA binding domains that contact the double helix, including a so-called "invariant asparagine." However, in about half of the bZIPs of Phytophthora infestans and other oomycetes this asparagine is replaced by cysteine. Knockdowns of the novel cysteine-containing bZIPs resulted in poor tolerance of oxidative stress, leading to the proposition that the cysteine is a redox switch affecting cellular defense networks. This will be tested by a multidisciplinary approach integrating protein biochemistry, bioinformatics, cell biology, metabolite analysis, and molecular genetics. Experiments will define the promoter motifs targeted by the bZIPs, dimerization partners of the bZIPs, and how DNA binding and dimerization are affected by cysteine oxidation. Cellular markers of the redox state will place bZIP behavior in context with what transpires during growth and development. Overall, the research will reveal how regulatory mechanisms have evolved during the eukaryotic radiation and help define pathways affecting growth and development in oomycetesThis 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.