An unreported NB ‐ LRR protein SUT 1 is required for the autoimmune response mediated by type one protein phosphatase 4 mutation (topp4‐1) in Arabidopsis

Summary Our previous study indicates that protein phosphatase 1 ( PP 1) is involved in plant immunity. To elucidate the underlying molecular mechanism, a genetic screening assay was carried out to identify suppressors of type one protein phosphatase 4 mutation ( topp4‐1 ) ( sut ). Molecular and genetic approaches were used to investigate the mechanism of activation of autoimmune response in topp4‐1 . We performed a map‐based cloning assay to identify the SUT 1 gene, which encodes a coiled‐coil nucleotide‐binding leucine‐rich‐repeat ( NB ‐ LRR ) protein ( CNL ). SUT 1 physically interacts with TYPE ONE PROTEIN PHOSPHATASE 4 ( TOPP 4) and topp4‐1. The mutated topp4‐1 protein activates the autoimmune response in the cytoplasm and promotes the accumulation of SUT 1 at both the transcription and the protein levels. Furthermore, our genetic and physical interactions confirm that the topp4‐1‐induced autoimmune responses are probably mediated by HEAT SHOCK PROTEIN 90 ( HSP 90) and REQUIRED FOR MLA 12 RESISTANCE 1 ( RAR 1). This study reveals that TOPP 4 phosphatase is likely guarded by SUT 1 in plant immunity.