Os<scp>CERK</scp>1 and Os<scp>RLCK</scp>176 play important roles in peptidoglycan and chitin signaling in rice innate immunity

<jats:title>Summary</jats:title><jats:p>Microbe‐associated molecular pattern (<jats:styled-content style="fixed-case">MAMP</jats:styled-content>)‐triggered immunity plays critical roles in the basal resistance defense response in plants. Chitin and peptidoglycan (<jats:styled-content style="fixed-case">PGN</jats:styled-content>) are major molecular patterns for fungi and bacteria, respectively. Two rice (<jats:italic>Oryza sativa</jats:italic>) lysin motif‐containing proteins, Os<jats:styled-content style="fixed-case">LYP</jats:styled-content>4 and Os<jats:styled-content style="fixed-case">LYP</jats:styled-content>6, function as receptors that sense bacterial <jats:styled-content style="fixed-case">PGN</jats:styled-content> 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<jats:styled-content style="fixed-case">CERK</jats:styled-content>1, a key component of the chitin elicitor signaling pathway, also plays an important role in <jats:styled-content style="fixed-case">PGN</jats:styled-content>‐triggered immunity in rice. Silencing of <jats:italic>Os<jats:styled-content style="fixed-case">CERK</jats:styled-content>1</jats:italic> suppressed <jats:styled-content style="fixed-case">PGN</jats:styled-content>‐induced (and chitin‐induced) immunity responses, including reactive oxygen species generation, defense gene expression, and callose deposition, indicating that Os<jats:styled-content style="fixed-case">CERK</jats:styled-content>1 is essential for both <jats:styled-content style="fixed-case">PGN</jats:styled-content> and chitin signaling initiated by Os<jats:styled-content style="fixed-case">LYP</jats:styled-content>4 and Os<jats:styled-content style="fixed-case">LYP</jats:styled-content>6. Os<jats:styled-content style="fixed-case">LYP</jats:styled-content>4 associated with Os<jats:styled-content style="fixed-case">LYP</jats:styled-content>6 and the rice chitin receptor chitin oligosaccharide elicitor‐binding protein (<jats:styled-content style="fixed-case">CEB</jats:styled-content>iP) in the absence of <jats:styled-content style="fixed-case">PGN</jats:styled-content> or chitin, and treatment with <jats:styled-content style="fixed-case">PGN</jats:styled-content> or chitin led to their disassociation <jats:italic>in vivo</jats:italic>. Os<jats:styled-content style="fixed-case">CERK</jats:styled-content>1 associated with Os<jats:styled-content style="fixed-case">LYP</jats:styled-content>4 or Os<jats:styled-content style="fixed-case">LYP</jats:styled-content>6 when induced by <jats:styled-content style="fixed-case">PGN</jats:styled-content> but it associated with Os<jats:styled-content style="fixed-case">LYP</jats:styled-content>4, Os<jats:styled-content style="fixed-case">LYP</jats:styled-content>6, or <jats:styled-content style="fixed-case">CEB</jats:styled-content>iP under chitin treatment, suggesting the presence of different patterns of ligand‐induced heterooligomeric receptor complexes. Furthermore, the receptor‐like cytoplasmic kinase Os<jats:styled-content style="fixed-case">RLCK</jats:styled-content>176 functions downstream of Os<jats:styled-content style="fixed-case">CERK</jats:styled-content>1 in the <jats:styled-content style="fixed-case">PGN</jats:styled-content> and chitin signaling pathways, suggesting that these <jats:styled-content style="fixed-case">MAMP</jats:styled-content>s share overlapping intracellular signaling components. Therefore, Os<jats:styled-content style="fixed-case">CERK</jats:styled-content>1 plays dual roles in <jats:styled-content style="fixed-case">PGN</jats:styled-content> and chitin signaling in rice innate immunity and as an adaptor involved in signal transduction at the plasma membrane in conjunction with Os<jats:styled-content style="fixed-case">LYP</jats:styled-content>4 and Os<jats:styled-content style="fixed-case">LYP</jats:styled-content>6.</jats:p>