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Microbe-associated molecular pattern (MAMP)-triggered immunity plays critical roles in the basal resistance defense response in plants. Chitin and peptidoglycan (PGN) are major molecular patterns for fungi and bacteria, respectively. Two rice (Oryza sativa) lysin motif-containing proteins, OsLYP4 and OsLYP6, function as receptors that sense bacterial PGN and fungal chitin. These membrane receptors, which lack intracellular kinase domains, likely contain another component for transmembrane immune signal transduction. Here, we demonstrate that the rice LysM receptor-like kinase OsCERK1, a key component of the chitin elicitor signaling pathway, also plays an important role in PGN-triggered immunity in rice. Silencing of OsCERK1 suppressed PGN-induced (and chitin-induced) immunity responses, including reactive oxygen species generation, defense gene expression, and callose deposition, indicating that OsCERK1 is essential for both PGN and chitin signaling initiated by OsLYP4 and OsLYP6. OsLYP4 associated with OsLYP6 and the rice chitin receptor chitin oligosaccharide elicitor-binding protein (CEBiP) in the absence of PGN or chitin, and treatment with PGN or chitin led to their disassociation in vivo. OsCERK1 associated with OsLYP4 or OsLYP6 when induced by PGN but it associated with OsLYP4, OsLYP6, or CEBiP under chitin treatment, suggesting the presence of different patterns of ligand-induced heterooligomeric receptor complexes. Furthermore, the receptor-like cytoplasmic kinase OsRLCK176 functions downstream of OsCERK1 in the PGN and chitin signaling pathways, suggesting that these MAMPs share overlapping intracellular signaling components. Therefore, OsCERK1 plays dual roles in PGN and chitin signaling in rice innate immunity and as an adaptor involved in signal transduction at the plasma membrane in conjunction with OsLYP4 and OsLYP6., (© 2014 The Authors The Plant Journal © 2014 John Wiley & Sons Ltd.)

The mitogen-activated protein kinase (MAPK) phosphatases (MKPs) are important negative regulators in the MAPK signaling pathways, which play crucial roles in plant growth, regulation of development and response to environment stresses. Several MAPKs have been reported to be involved in the drought stress response, however, there is no evidence for the specific function of MKPs in drought stress. Here, a putative MKP in rice (Oryza sativa), OsIBR5, was characterized. Expression of OsIBR5 was induced by PEG6000, abscisic acid (ABA) and hydrogen peroxide (H(2)O(2)). Overexpression of OsIBR5 in tobacco plants resulted in hypersensitivity to drought and H(2)O(2) treatments. Drought and ABA-induced stomatal closure was significantly reduced in OsIBR5-overexpressing tobacco plants compared with controls. Moreover, OsIBR5 was found to interact with tobacco MAPKs SIPK and WIPK, and drought-induced WIPK activity was impaired in OsIBR5-overexpressing tobacco plants. These results indicated that OsIBR5 is a MKP which was induced by abiotic stresses and decreased tolerance to drought stress in transgenic tobacco plants., (Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.)

Microbe-associated molecular pattern ( MAMP)-triggered immunity plays critical roles in the basal resistance defense response in plants. Chitin and peptidoglycan ( PGN) are major molecular patterns for fungi and bacteria, respectively. Two rice ( Oryza sativa) lysin motif-containing proteins, Os LYP4 and Os LYP6, function as receptors that sense bacterial PGN and fungal chitin. These membrane receptors, which lack intracellular kinase domains, likely contain another component for transmembrane immune signal transduction. Here, we demonstrate that the rice LysM receptor-like kinase Os CERK1, a key component of the chitin elicitor signaling pathway, also plays an important role in PGN-triggered immunity in rice. Silencing of Os CERK1 suppressed PGN-induced (and chitin-induced) immunity responses, including reactive oxygen species generation, defense gene expression, and callose deposition, indicating that Os CERK1 is essential for both PGN and chitin signaling initiated by Os LYP4 and Os LYP6. Os LYP4 associated with Os LYP6 and the rice chitin receptor chitin oligosaccharide elicitor-binding protein ( CEBiP) in the absence of PGN or chitin, and treatment with PGN or chitin led to their disassociation in vivo. Os CERK1 associated with Os LYP4 or Os LYP6 when induced by PGN but it associated with Os LYP4, Os LYP6, or CEBiP under chitin treatment, suggesting the presence of different patterns of ligand-induced heterooligomeric receptor complexes. Furthermore, the receptor-like cytoplasmic kinase Os RLCK176 functions downstream of Os CERK1 in the PGN and chitin signaling pathways, suggesting that these MAMPs share overlapping intracellular signaling components. Therefore, Os CERK1 plays dual roles in PGN and chitin signaling in rice innate immunity and as an adaptor involved in signal transduction at the plasma membrane in conjunction with Os LYP4 and Os LYP6. [ABSTRACT FROM AUTHOR]