Translating extracellular ligand perception into a cytosolic Ca2+ signal: characterizing the role plant elicitor peptides and their receptor play in innate immune responses

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This project focuses on a signal transduction system involved in plant cell immune signaling; an overall aim is to identify molecular mechanisms that allow perception of pathogenic microbes by plant cell membrane receptor proteins and translation of this perception to defense responses. An essential step in the signaling cascade is a cytosolic Ca2+ elevation that evokes downstream defense programs. Studies will focus on a family of Plant Elicitor Peptides (Peps) and their cell membrane receptor (PEPR1). A model of how Pep binding to the PEPR1 receptor leads to cytosolic Ca2+ elevation will be tested by the investigators. Preliminary studies undertaken by the investigators indicate that the PEPR1 receptor has guanylyl cyclase activity. The project will investigate whether cyclic guanylyl monophosphate (cGMP), a signaling molecule in cells, is generated in plant cells by the receptor in response to pathogen cues causing Pep peptide generation, and if the cGMP production elevates cytosolic Ca2+ due to the opening of a cyclic nucleotide gated ion channel in the cell membrane. These early steps in the immune signaling cascade will be linked to downstream defense responses such as the generation of antimicrobial molecules that limit growth of a virulent pathogen (Pseudomonas syringae) and hypersensitive response/programmed cell death response to an avirulent pathogen (P. syringae avrRpt2).The Principal Investigator of the project has a history of recruiting high school students to work with graduate students in the laboratory, as well as accessing minority undergraduate programs and involving these students in research. This outreach and training will continue during the proposed project. The Principal Investigator has an ongoing interaction with a biology teacher at a local high school and will work with this teacher to recruit high school students to participate, along with undergraduate students, in the research activity of the project.