The rice LysM receptor‐like kinase <i>Os</i><scp>CERK</scp>1 is required for the perception of short‐chain chitin oligomers in arbuscular mycorrhizal signaling

<jats:title>Summary</jats:title><jats:p> <jats:list list-type="bullet"> <jats:list-item><jats:p>The rice lysin‐motif (LysM) receptor‐like kinase <jats:italic>Os</jats:italic><jats:styled-content style="fixed-case">CERK</jats:styled-content>1 is now known to have a dual role in both pathogenic and symbiotic interactions. Following the recent discovery that the <jats:italic>Oscerk1</jats:italic> mutant is unable to host arbuscular mycorrhizal (<jats:styled-content style="fixed-case">AM</jats:styled-content>) fungi, we have examined whether <jats:italic>Os</jats:italic><jats:styled-content style="fixed-case">CERK</jats:styled-content>1 is directly involved in the perception of the short‐chain chitin oligomers (Myc‐<jats:styled-content style="fixed-case">CO</jats:styled-content>s) identified in <jats:styled-content style="fixed-case">AM</jats:styled-content> fungal exudates and shown to activate nuclear calcium (Ca<jats:sup>2+</jats:sup>) spiking in the rice root epidermis.</jats:p></jats:list-item> <jats:list-item><jats:p>An <jats:italic>Oscerk1</jats:italic> knockout mutant expressing the cameleon <jats:styled-content style="fixed-case">NLS</jats:styled-content>‐<jats:styled-content style="fixed-case">YC</jats:styled-content>2.60 was used to monitor nuclear Ca<jats:sup>2+</jats:sup> signaling following root treatment with either crude fungal exudates or purified Myc‐<jats:styled-content style="fixed-case">CO</jats:styled-content>s.</jats:p></jats:list-item> <jats:list-item><jats:p>Compared with wild‐type rice, Ca<jats:sup>2+</jats:sup> spiking responses to <jats:styled-content style="fixed-case">AM</jats:styled-content> fungal elicitation were absent in root atrichoblasts of the <jats:italic>Oscerk1</jats:italic> mutant. By contrast, rice lines mutated in <jats:italic>Os<jats:styled-content style="fixed-case">CEB</jats:styled-content>iP</jats:italic>, encoding the LysM receptor‐like protein which associates with <jats:italic>Os</jats:italic><jats:styled-content style="fixed-case">CERK</jats:styled-content>1 to perceive chitin elicitors of the host immune defense pathway, responded positively to Myc‐<jats:styled-content style="fixed-case">CO</jats:styled-content>s.</jats:p></jats:list-item> <jats:list-item><jats:p>These findings provide direct evidence that the bi‐functional <jats:italic>Os</jats:italic><jats:styled-content style="fixed-case">CERK</jats:styled-content>1 plays a central role in perceiving short‐chain Myc‐<jats:styled-content style="fixed-case">CO</jats:styled-content> signals and activating the downstream conserved symbiotic signal transduction pathway.</jats:p></jats:list-item> </jats:list> </jats:p>