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Walter Gassmann

Date & Location: February 7, 2022, at 4p

Location: MPS 1200

Subject: The plant innate immune system: where to begin and where to end?

Host: Deepak Bhandari

About the Speaker

Institution: University of Missouri

Abstract: The plant immune system is intricately embedded in normal plant functions targeted by pathogens and needs to be tightly controlled to enable healthy plant growth. The balance between immunity and growth therefore occurs on multiple levels and is not fully understood. Using Arabidopsis genetics my lab identified the adaptor protein SRFR1 that negatively regulates immune signaling triggered by bacterial and other pathogens. SRFR1 encodes a pioneer tetratricopeptide repeat (TPR) protein conserved between plants and animals. The SRFR1 TPR domain has significant sequence similarity to those of transcriptional repressors in yeast and Caenorhabditis elegans. A functional sub-pool of SRFR1 localizes to the nucleus, and we identified members of the TCP transcription factor family as nuclear interactors of SRFR1, an intriguing finding since TCPs mainly were implicated in developmental processes. Using ChIP-Seq and RNA-Seq we could demonstrate that SRFR1-interacting TCPs are involved in regulating several hormonal pathways. We therefore propose that nuclear SRFR1 functions in a transcriptional repressor complex that balances plant biotic stress resistance and development. A second class of SRFR1 interactors includes immune regulators such as EDS1 and TNL resistance proteins. Following up on the observation that the bacterial effector AvrRps4 directly interacts with EDS1 and disrupts interactions of EDS1 with SRFR1, we discovered that AvrRps4 is a bipartite effector, with both peptides of processed AvrRps4 necessary for triggering resistance in Arabidopsis. In contrast, the N-terminal AvrRps4 fragment (AvrRps4-N) was sufficient to trigger resistance in lettuce. Our ongoing research aims to establish the function of AvrRps4-N and how SRFR1 may differentially modulate regulatory complexes that are targeted by effectors and guarded by resistance proteins.