CEBiP is the major chitin oligomer-binding protein in rice and plays a main role in the perception of chitin oligomers

Abstract

CEBiP, a plasma membrane-localized glycoprotein of rice, directly binds with chitin elicitors (CE), and has been identified as a receptor for CE by using CEBiP-RNAi rice cells. To further clarify the function of CEBiP, we produced CEBiP-disrupted rice plants by applying an efficient Agrobacterium-mediated gene-targeting system based on homologous recombination, which has recently been developed for rice. Homologous recombination occurred at the CEBiP locus in ~0.5 % of the positive/negative selected calli. In the self-pollinated next generation, it was confirmed that the first exon of CEBiP was replaced with the hygromycin selection cassette as designed, and that the expression of CEBiP was completely deficient in homozygous cebip lines. Affinity-labeling analysis using biotinylated N-acetylchitooctaose demonstrated that CEBiP is the major CE-binding protein in rice cultured cells and leaves, which was consistent with the result that the response to CE in cebip cells was greatly diminished. Nevertheless, we observed a significant decrease in disease resistance against Magnaporthe oryzae, the causal agent of rice blast disease, only when the cebip leaf sheaths were inoculated with a weakly virulent strain, suggesting that CE perception during the infection process of M. oryzae is limited. The response to peptidoglycan and lipopolysaccharides in cebip cells was not affected, strongly suggesting that CEBiP is a CE-specific receptor.

Turnabout Is Fair Play: Herbivory-Induced Plant Chitinases Excreted in Fall Armyworm Frass Suppress Herbivore Defenses in Maize

“…The receptors that bind chitin oligomers and induce pathogen defenses in rice (Oryza sativa) and Arabidopsis (Arabidopsis thaliana) also have been identified (Wan et al, 2012;Tanaka et al, 2013;Kouzai et al, 2014). However, to our knowledge, there has been no previous report that chitinases may be involved in eliciting plant defenses.…”

Chitin and chitin-related compounds in plant–fungal interactions

“…CEBiP is typical receptor-like protein (RLP) with an extracellular domain containing two predicted lysin motifs (LysMs) at the N terminus and a short membrane-spanning domain at the C terminus and lacks cytoplasmic kinase domain but directly involved in chitin-triggered immunity (Kouzai et al 2014). …”

Chitin-mediated plant–fungal interactions: catching, hiding and handshaking

“…OsCEBiP and OsCERK1 were shown to form a receptor complex ligand dependently, which seems to trigger downstream signaling. Knockdown/ knockout of OsCEBiP coupled with affinity labeling experiments showed that OsCEBiP is the major receptor for chitin oligosaccharides in rice, whereas OsCERK1 did not bind chitin oligosaccharides or colloidal chitin [14,17,18]. Epitope mapping by NMR spectroscopy combined with molecular modeling/docking studies and binding studies indicated that two molecules of OsCEBiP simultaneously bind to one chitin oligosaccharide from the opposite surface, interacting with N-acetyl groups in the internal GlcNAc residues, and form a homo-dimer ( Figure 2a) [19 ].…”

“…However, as the knockout of OsCEBiP resulted in the disappearance of most chitin oligosaccharide binding proteins in the plasma membrane and also chitin-induced defense responses [18], it is not clear to what degree OsLYP4 and OsLYP6 contribute to chitin signaling in rice.…”

“…These results clearly indicate the dual function of OsCERK1 in innate immunity and AM symbiosis. Because a knockout mutant of OsCEBiP [18] established mycorrhizal symbiosis normally [58 ], the signaling pathways downstream of OsCERK1 should be different between AM symbiosis and chitin-triggered immunity, and OsCERK1 but not chitin-triggered immunity is required for AM symbiosis. It is well established that the OsCERK1-OsCEBiP complex mediates chitin perception and signaling [16,19 ] but it remains for future studies to determine how OsCERK1 is involved in the perception of Myc signals in AM symbiosis.…”