E3 ligase SAUL1 serves as a positive regulator of PAMP‐triggered immunity and its homeostasis is monitored by immune receptor SOC3

What is it about?

In both plants and animals, intracellular immune receptors recognize pathogen-derived molecules and mount effective immune responses against microbial infections. These plant immune receptors often guard the presence or activity of other host proteins, which are the direct virulence targets of pathogen effectors. The guardees are often immune-promoting components such as those in a MAP kinase cascade. Plant E3 ligases serve many roles in immune regulation, but it is unclear whether they can also be guarded by immune receptors. Here, we report on an immune-regulating E3 ligase SAUL1, whose homeostasis is monitored by a Toll Interleukin 1 Receptor (TIR)-type immune receptor, SOC3. SOC3 can associate with SAUL1, and either loss or overexpression of SAUL1 triggers autoimmunity mediated by SOC3. On the other hand, SAUL1 functions redundantly with its close homolog PUB43 to promote PAMP-triggered immunity (PTI). Taken together, the E3 ligase SAUL1 serves as a positive regulator of PTI and its homeostasis is monitored by the TNL SOC3.

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