Two LysM receptor molecules, CEBiP and OsCERK1, cooperatively regulate chitin elicitor signaling in rice

Abstract

Chitin is a major molecular pattern for various fungi, and its fragments, chitin oligosaccharides, are known to induce various defense responses in plant cells. A plasma membrane glycoprotein, CEBiP (chitin elicitor binding protein) and a receptor kinase, CERK1 (chitin elicitor receptor kinase) (also known as LysM-RLK1), were identified as critical components for chitin signaling in rice and Arabidopsis, respectively. However, it is not known whether each plant species requires both of these two types of molecules for chitin signaling, nor the relationships between these molecules in membrane signaling. We report here that rice cells require a LysM receptor-like kinase, OsCERK1, in addition to CEBiP, for chitin signaling. Knockdown of OsCERK1 resulted in marked suppression of the defense responses induced by chitin oligosaccharides, indicating that OsCERK1 is essential for chitin signaling in rice. The results of a yeast two-hybrid assay indicated that both CEBiP and OsCERK1 have the potential to form hetero- or homo-oligomers. Immunoprecipitation using a membrane preparation from rice cells treated with chitin oligosaccharides suggested the ligand-induced formation of a receptor complex containing both CEBiP and OsCERK1. Blue native PAGE and chemical cross-linking experiments also suggested that a major portion of CEBiP exists as homo-oligomers even in the absence of chitin oligosaccharides.

Chitin and chitin-related compounds in plant–fungal interactions

“…In the situation of defence responses to pathogenic fungi, LysM RLK1 (Wan et al 2008) or CERK1 (Miya et al 2007)/CERK1 (as in Arabidopsis ) or CERK1/CEBiP receptor dimers (as in rice, Shimizu et al 2010) needs longer chito-oligomers, like octamers to activate its response through heterodimerisation (Hayafune et al 2014; Liu et al 2015). The perception of shorter oligosaccharides such as chitotetraose could instead rely on monomeric receptors (Miyata et al 2014; Shinya et al 2015) as into each receptor’s LysM domain, half of this oligomer molecule (C4) fits (Liu et al 2012; Shinya et al 2015).…”

OsLYP4 and OsLYP6 play critical roles in rice defense signal transduction

“…Shimizu et al has found that a major portion of CEBiP proteins were visualized as homodimers by the blue native PAGE analysis. 13 However, a small fraction of CEBiP proteins did exist as larger-size oligomers, 13 which may suggest that some CEBiP proteins can be in the same complexes with OsLYP4 and OsLYP6. Our data that CEBiP interacted with OsLYP4 in yeast and in plant cells (Fig.…”

“…2A, and reviewed in ref. 13), and these OsLYPs apparently need a signaling partner (e.g., OsCERK1) 13 with an intracellular kinase domain for defense signal transduction, the composition and the stoichiometry of different chitin or PGN receptor complexes in rice await further investigation, which will shed new light on the rice innate immunity.…”

The Ankyrin-Repeat Transmembrane Protein BDA1 Functions Downstream of the Receptor-Like Protein SNC2 to Regulate Plant Immunity

“…The receptor-like kinase BAK1 functions as a coreceptor of FLS2 and EFR in the perception of bacterial flagellin and translation elongation factor EF-Tu (Chinchilla et al, 2007;Heese et al, 2007;Schulze et al, 2010;Roux et al, 2011). In rice (Oryza sativa), CERK1 functions together with the lysin motif (LysM) domain protein CEBiP to recognize the fungal cell wall component chitin (Shimizu et al, 2010). Together with two other LysM domain proteins, LYM1 and LYM3, Arabidopsis (Arabidopsis thaliana) CERK1 is also involved in the perception of bacterial peptidoglycan (Willmann et al, 2011).…”