Os09g0511000

The rice gene Os09g0511000 is known as OsCERK1. OsCERK1 encodes a receptor-like kinase called OsCERK1 which is essential for chitin elicitor signaling in rice cells.

Annotated Information

Function

OsCERK1 encoded a receptor-like kinase called OsCERK1

OsCERK1 encoded a receptor-like kinase consisting of 624 amino acid residues, containing a signal peptide, an extracellular domain, a transmembrane region and an intracellular Ser/Thr kinase domain (Figure 1).

Figure 1 Amino acid sequence of OsCERK1 predicted from the cDNA. Underlining indicates the sequence corresponding to the LysM motif. EC, extracellular domain; IC, intracellular domain; SP, signal peptide; TM, transmembrane domain.

OsCERK1 is a plasma membrane protein containing one LysM motif in the extracellular domain and an intracellular Ser/Thr kinase domain.

OsCERK1 is essential for chitin elicitor signaling in rice cells

Knockdown of OsCERK1 resulted in a marked suppression of the defense responses in rice cells induced by chitin oligosaccharides, indicating a central role for OsCERK1 in chitin signaling in rice. The results of yeast two-hybrid assay indicate that the extracellular domain of OsCERK1 can interact with that of CEBiP, suggesting that OsCERK1 and CEBiP have the potential to form homo- and hetero-oligomers through interaction of their LysM-containing extracellular domains. These results indicated that, in the absence of chitin oligosaccharide elicitor, a major portion of CEBiP exists most likely as homo-oligomers in the plasma membrane, whereas OsCERK1 is mostly present as a monomer. However, when the chitin oligosaccharide elicitor is added to the cells, a portion of CEBiP and OsCERK1 appear to form a hetero-oligomer receptor complex. Other researchers also confirm that these two proteins form a receptor complex that transduces the chitin signal to downstream components for immune responses.

OsCERK1 signal pathway

OsRacGEF1 as a guanine nucleotide exchange factor for OsRac1 (rice small GTPase). OsRacGEF1 interacts with OsCERK1 and is activated when its C-terminal S549 is phosphorylated by the cytoplasmic domain of OsCERK1 in response to chitin. Activated OsRacGEF1 is required for chitin-driven immune responses and resistance to rice blast fungus infection. Further, a protein complex including OsCERK1 and OsRacGEF1 is transported from the endoplasmic reticulum to the PM. OsCEBiP, OsCERK1, OsRacGEF1, and OsRac1 function as key components of a ‘‘defensome’’ critically engaged early during chitin-induced immunity.

Expression

Figure 2 Expression patterns of the OsCERK1 gene in each part of the rice plant. Sh, shoot; R, root; PS, proximal shoot; St, stem; F, flower

OsCERK1 was expressed in all tissues tested, with weak expression in the flowers (Figure 2).

Evolution

Phylogenies were analyzed by multiple sequence alignment of the protein sequences of the LysM receptor-like kinases. The names of proteins described previously (Zhang et al., 2007) are shown in parentheses for ease of comparison.

Figure 3 Phylogenetic tree of OsCERK1 and related plant LysM receptor-like kinases.

The scale indicates the base substitution rate, and numbers at the nodes represent bootstrap values with 1000 replicates (Figure 3).

Labs working on this gene

• Department of Life Sciences, Faculty of Agriculture, Meiji University, 1-1-1 Higashi-Mita, Tama-ku, Kawasaki, Kanagawa 214-8571, Japan
• Division of Plant Sciences, National Institute of Agrobiological Sciences, 2-1-2 Kannondai, Tsukuba, Ibaraki 305-8602, Japan
• Biotechnology Research Center, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
• Laboratory of Plant Molecular Genetics, Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192, Japan
• Agricultural and Veterinary Research Laboratories, Meiji Seika Kaisha, Kohoku-ku, Yokohama 222–8567, Japan