Systemin, the first peptide hormone identified in plants, was initially isolated from tomato(Solanum lycopersicum) leaves. Systemin mediates local and systemic wound-induced defense responses in plants, conferring res...Systemin, the first peptide hormone identified in plants, was initially isolated from tomato(Solanum lycopersicum) leaves. Systemin mediates local and systemic wound-induced defense responses in plants, conferring resistance to necrotrophic fungi and herbivorous insects. Systemin is recognized by the leucine-rich-repeat receptor-like kinase(LRRRLK) receptor SYSTEMIN RECEPTOR1(SYR1), but how the systemin recognition signal is transduced to intracellular signaling pathways to trigger defense responses is poorly understood. Here, we demonstrate that SERK family LRR-RLKs function as coreceptors for SYR1 to mediate systemin signal transduction in tomato. By using chemical genetic approaches coupled with engineered receptors, we revealed that the association of the cytoplasmic kinase domains of SYR1 with SERKs leads to their mutual trans-phosphorylation and the activation of SYR1, which in turn induces a wide range of defense responses. Systemin stimulates the association between SYR1 and all tomato SERKs(SlSERK1,SlSERK3A, and SlSERK3B). The resulting SYR1-SlSERK heteromeric complexes trigger the phosphorylation of TOMATO PROTEIN KINASE 1B(TPK1b), a receptor-like cytoplasmic kinase that positively regulates systemin responses. Additionally,upon association with SYR1, SlSERKs are cleaved by the Pseudomonas syringae effector HopB1, further supporting the finding that SlSERKs are activated by systemin-bound SYR1. Finally, genetic analysis using Slserk mutants showed that SlSERKs are essential for systemin-mediated defense responses. Collectively, these findings demonstrate that the systeminmediated association of SYR1 and SlSERKs activates defense responses against herbivorous insects.展开更多
Wound-inducible proteinase inhibitors （PIs） in tomato plants provide a useful model system to elucidate the signal transduction pathways that regulate systemic defense response. Among the proposed intercellular sign...Wound-inducible proteinase inhibitors （PIs） in tomato plants provide a useful model system to elucidate the signal transduction pathways that regulate systemic defense response. Among the proposed intercellular signals for wound-induced PIs expression are the peptide systemin and the oxylipin-derived phytohormone jasmonic acid （JA）. An increasing body of evidence indicates that systemin and JA work in the same signaling pathway to activate the ex- pression of PIs and other defense-related genes. However, relatively less is known about how these signals interact to promote cell-to-cell communication over long distances. Genetic analysis of the systemin/JA signaling pathway in tomato plants provides a unique opportunity to study, in a single experimental system, the mechanism by which peptide and oxylipin signals interact to coordinate systemic expression of defense-related genes. Previously, it has been proposed that systemin is the long-distance mobile signal for defense gene expression. Recently, grafting experiments with tomato mutants defective in JA biosynthesis and signaling provide new evidence that JA, rather than systemin, functions as the systemic wound signal, and that the biosynthesis of JA is regulated by the peptide systemin. Further understanding of the systemin/JA signaling pathway promises to provide new insights into the basic mechanisms governing plant defense to biotic stress.展开更多
基金supported by the National Research Foundation of Korea Grant funded by the Korean Government (NRF-2022R1A4A3024451 and NRF2023R1A2C3002386)a grant from Korea University。
文摘Systemin, the first peptide hormone identified in plants, was initially isolated from tomato(Solanum lycopersicum) leaves. Systemin mediates local and systemic wound-induced defense responses in plants, conferring resistance to necrotrophic fungi and herbivorous insects. Systemin is recognized by the leucine-rich-repeat receptor-like kinase(LRRRLK) receptor SYSTEMIN RECEPTOR1(SYR1), but how the systemin recognition signal is transduced to intracellular signaling pathways to trigger defense responses is poorly understood. Here, we demonstrate that SERK family LRR-RLKs function as coreceptors for SYR1 to mediate systemin signal transduction in tomato. By using chemical genetic approaches coupled with engineered receptors, we revealed that the association of the cytoplasmic kinase domains of SYR1 with SERKs leads to their mutual trans-phosphorylation and the activation of SYR1, which in turn induces a wide range of defense responses. Systemin stimulates the association between SYR1 and all tomato SERKs(SlSERK1,SlSERK3A, and SlSERK3B). The resulting SYR1-SlSERK heteromeric complexes trigger the phosphorylation of TOMATO PROTEIN KINASE 1B(TPK1b), a receptor-like cytoplasmic kinase that positively regulates systemin responses. Additionally,upon association with SYR1, SlSERKs are cleaved by the Pseudomonas syringae effector HopB1, further supporting the finding that SlSERKs are activated by systemin-bound SYR1. Finally, genetic analysis using Slserk mutants showed that SlSERKs are essential for systemin-mediated defense responses. Collectively, these findings demonstrate that the systeminmediated association of SYR1 and SlSERKs activates defense responses against herbivorous insects.
文摘Wound-inducible proteinase inhibitors （PIs） in tomato plants provide a useful model system to elucidate the signal transduction pathways that regulate systemic defense response. Among the proposed intercellular signals for wound-induced PIs expression are the peptide systemin and the oxylipin-derived phytohormone jasmonic acid （JA）. An increasing body of evidence indicates that systemin and JA work in the same signaling pathway to activate the ex- pression of PIs and other defense-related genes. However, relatively less is known about how these signals interact to promote cell-to-cell communication over long distances. Genetic analysis of the systemin/JA signaling pathway in tomato plants provides a unique opportunity to study, in a single experimental system, the mechanism by which peptide and oxylipin signals interact to coordinate systemic expression of defense-related genes. Previously, it has been proposed that systemin is the long-distance mobile signal for defense gene expression. Recently, grafting experiments with tomato mutants defective in JA biosynthesis and signaling provide new evidence that JA, rather than systemin, functions as the systemic wound signal, and that the biosynthesis of JA is regulated by the peptide systemin. Further understanding of the systemin/JA signaling pathway promises to provide new insights into the basic mechanisms governing plant defense to biotic stress.
