Adapting to challenges: functions of the Arabidopsis immune adaptor SRFR1 and associated proteins
Plant immunity needs to be tightly controlled to enable normal plant growth. The balance between immunity and growth occurs on multiple levels and is not fully understood. Using Arabidopsis genetics, Gassmann's lab identified the adaptor protein SRFR1 that negatively regulates immune signaling triggered by bacterial pathogens. A functional sub-pool of SRFR1 localizes to the nucleus, where it interacts with members of the TCP transcription factor family. TCP transcription factors mainly have been described as regulating developmental processes. They therefore proposed that nuclear SRFR1 functions in a transcriptional repressor complex that balances plant biotic stress resistance. A second class of SRFR1 interactors consists of immune regulators such as EDS1 and TNL resistance proteins. Following up on the observation that the bacterial effector AvrRps4 directly interacts with EDS1, they discovered that AvrRps4 is a bipartite effector, with both peptides of processed AvrRps4 necessary for triggering resistance. They propose that SRFR1 and EDS1 may differentially modulate transcriptional regulatory complexes that are targeted by effectors and guarded by resistance proteins.
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