Untangling the Complex Network of BIK1 Mediated Immune Response Signaling Pathways

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Plant pathogens pose continued threat to global crop production. Studies that expand fundamental knowledge on mechanisms of plant-pathogen interaction will ultimately help design better disease control strategies. Despite extensive studies, mechanisms regulating pathogen recognition, signal transduction and activation of plant defenses are poorly understood, particularly for interactions involving fungi that kill host tissue in order to gain access to a plant's nutrients. These so-called necrotrophic pathogens promote the destruction of their plant hosts by secreting a variety of disease promoting factors. The goal of this project is to determine how plants recognize that an infection was initiated and the molecular and cellular processes plants employ to activate appropriate defenses. This project will also provide training for students and postdoctoral scientists.Arabidopsis BOTRYTIS-INDUCED KINASE1 (BIK1) plays a central role in plant immunity to necrotrophic fungi and bacterial pathogens. BIK1 promotes resistance to necrotrophic fungi but suppresses resistance to virulent strains of the biotrophic bacterial pathogen Pseudomonas syringae. Intriguingly, BIK1 promotes PAMP triggered immunity (PTI) to bacterial and fungal pathogens. The PTI function of BIK1 hinges upon ethylene signaling and interactions with other immune response regulators. Thus, BIK1 is pervasive in its impact on plant immune and hormone responses, epitomizing the complexity of its functions. The molecular and biochemical bases of BIK1's functional versatility and regulatory role are not understood. The downstream targets that connect BIK1 to downstream immune responses that contribute to its contrasting resistance functions are not well studied. By taking BIK1 as a focal point, the project aims to dissect the molecular mechanisms of plant immune response signaling. First, targets of BIK1 that propagate signals downstream will be studied for their mechanisms of function in relation to BIK1 and other regulators of plant immunity. The regulatory relationship between BIK1 and its interacting partners will be studied through genetic, molecular and biochemical approaches. The goal is to determine biochemical and functional linkage between BIK1, its interacting partners and other targets further downstream in the immune response signaling hierarchy. Second, the biochemical and molecular interactions between BIK1 and other regulators of PTI and effector triggered immunity (ETI) will be studied to determine the role of BIK1 at the ETI-PTI interface. The relationship of BIK1 and receptor like kinases mediating responses to necrotrophic fungi will be investigated. This project will provide training to students and post-doctoral scientists of different backgrounds to contribute to a diverse scientific workforce. In addition, necrotrophic fungi are widespread pathogens with tremendous impacts on crop production. Virulence strategies of necrotrophs and the corresponding plant immune responses show significant differences from biotrophic pathogens. The project will pave the way for smarter genetic resistance strategies by generating fundamental knowledge on regulatory proteins and mechanisms that control plant immunity.