Plant surface immune receptors are tightly controlled to maintain homeostasis and prevent overactivation. However, the mechanisms coordinating the balance remain largely unknown. The monocot-specific receptor-like kinase SDS2 regulates cell death and immunity in rice. Here, we identify Thr671, a conserved phospho-switch in RD-type Ser/Thr kinases across kingdoms, as the central node that orchestrates both immune activation and turnover of SDS2. Autophosphorylation of Thr671 initiates signaling but also primes SDS2 for ubiquitination and degradation by the E3 ligase SPL11. This degradation is antagonized by the phosphatase SIPP1, which stabilizes SDS2 through Thr671 dephosphorylation to promote immunity. Strikingly, a second phosphatase, SIPP2, displaces SIPP1 from SDS2 via competitive binding, thereby enabling SPL11-dependent SDS2 degradation and ensuring timely immune attenuation. Thus, the SIPP1-SPL11-SIPP2 module establishes a dynamic equilibrium essential for SDS2 homeostasis, providing new insights into the sophisticated regulation of surface receptors.
Plants deploy intracellular nucleotide-binding leucine-rich repeat (NLR) immune receptors to detect pathogen-secreted virulence effectors and trigger defense responses. NLRs recognize effectors from both adapted and non-adapted pathogens (Dong et al., 2025), either through direct binding or by monitoring effector-induced modifications of host targets (Cesari et al., 2018). Despite these advances, the mechanism by which NLRs evolve new effector-recognition specificities remains a fundamental question in plant immunity. Recently, Gómez de la Cruz et al. (2026) uncovered a novel evolutionary strategy underlying the recognition of the blast fungus effector Pwl2 by the barley NLR MLA3, in which MLA3 acts as a molecular mimic of the effector's virulence target, the heavy metal-associated protein HIPP43 (Zdrzałek et al., 2024; Were et al., 2025). Importantly, the authors successfully transferred this molecular mimicry interface into the wheat stem rust resistance protein SR50, generating a chimeric NLR receptor with dual pathogen-recognition capabilities. The engineered receptor conferred resistance to both wheat stem rust, caused by Puccinia graminis f. sp. tritici (Pgt), and rice blast disease, caused by Magnaporthe oryzae, in transgenic barley, highlighting the potential of this strategy for developing broad-spectrum and durable disease resistance in crops.
Mengyu Qu, Ya Li, Fujia Yang et al.· Molecular Plant· 0 citations
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