Chen Yongming, Song Yingying, Tu Zhipeng, Bi Weishuai, Sun Congcong, Zhao Tingting, Wang Xiaodan, Dou Daolong, Xu Guangyuan
State Key Laboratory of Agricultural and Forestry Biosecurity, Ministry of Agriculture Key Lab of Pest Monitoring and Green Management, College of Plant Protection, China Agricultural University, Beijing 100193, China.
College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China.
Sci Adv. 2025 Apr 18;11(16):eadt2315. doi: 10.1126/sciadv.adt2315.
SUPPRESSOR OF BIR1-1 (SOBIR1) is a receptor-like kinase (RLK) that acts as a coreceptor for multiple receptor-like proteins (RLPs) to mediate pathogen-associated molecular pattern)-triggered immunity. However, the regulation of SOBIR1 homeostasis and activity remains largely unknown. Our study reveals that SOBIR1-ASSOCIATED PROTEIN KINASE 1 (SOAK1), a member of the receptor-like cytoplasmic kinase (RLCK)-V subfamily with a transmembrane domain, negatively regulates multiple RLP-mediated immune responses. SOAK1 constitutively interacts with SOBIR1 and modulates SOBIR1-dependent immune signaling. SOAK1 directly phosphorylates SOBIR1 at serine-406, substantially impairing its ability to transphosphorylate itself and BAK1. The conservation of serine-406 residue among various flowering plants suggests that phosphorylation at this site plays a critical role in regulating plant immunity. Conversely, SOBIR1 also phosphorylates SOAK1 primarily at serine-73, inhibiting SOAK1's kinase activity and derepressing SOBIR1 activity. This study elucidates a regulatory mechanism for SOBIR1 activity and highlights an uncharacterized role of RLCK-V subfamily members in plant immunity.
BIR1-1抑制因子（SOBIR1）是一种类受体激酶（RLK），作为多种类受体蛋白（RLP）的共受体，介导病原体相关分子模式触发的免疫反应。然而，SOBIR1稳态和活性的调控在很大程度上仍不清楚。我们的研究表明，SOBIR1相关蛋白激酶1（SOAK1）是类受体胞质激酶（RLCK）-V亚家族的成员，具有一个跨膜结构域，它对多种RLP介导的免疫反应起负调控作用。SOAK1持续与SOBIR1相互作用，并调节依赖SOBIR1的免疫信号传导。SOAK1直接在丝氨酸-406处磷酸化SOBIR1，显著损害其自身磷酸化和磷酸化BAK1的能力。各种开花植物中丝氨酸-406残基的保守性表明，该位点的磷酸化在调节植物免疫中起关键作用。相反，SOBIR1也主要在丝氨酸-73处磷酸化SOAK1，抑制SOAK1的激酶活性并解除对SOBIR1活性的抑制。这项研究阐明了SOBIR1活性的调控机制，并突出了RLCK-V亚家族成员在植物免疫中一个未被描述的作用。
