Functional characterization of CEBiP and CERK1 homologs in arabidopsis and rice reveals the presence of different chitin receptor systems in plants.
Chitin is a representative microbe-associated molecular pattern (MAMP) molecule for various fungi and induces immune responses in many plant species. It has been clarified that the chitin signaling in rice requires a receptor kinase OsCERK1 and a receptor-like protein (Os)CEBiP, which specifically binds chitin oligosaccharides. On the other hand, Arabidopsis requires a receptor kinase (At)CERK1 for chitin signaling but it is not clear whether the plant also requires a CEBiP-like molecule for chitin perception/signaling. To clarify the similarity/difference of the chitin receptor in these two model plants, we first characterized CEBiP homologs in Arabidopsis. Only one of three CEBiP homologs, AtCEBiP (LYM2), showed a high-affinity binding for chitin oligosaccharides similar to rice CEBiP. AtCEBiP also represented the major chitin-binding protein in the Arabidopsis membrane. However, the single/triple knockout (KO) mutants of Arabidopsis CEBiP homologs and the overexpressor of AtCEBiP showed chitin-induced defense responses similar to wild-type Arabidopsis, indicating that AtCEBiP is biochemically functional as a chitin-binding protein but does not contribute to signaling. Studies of the chitin binding properties of the ectodomains of At/OsCERK1 and the chimeric receptors consisting of ecto/cytosolic domains of these molecules indicated that AtCERK1 is sufficient for chitin perception by itself.
Department of Life Sciences, School of Agriculture, Meiji University, Kawasaki, Kanagawa, 214-8571 Japan.
Tomonori
T
Shinya
Noriko
N
Motoyama
Asahi
A
Ikeda
Miyuki
M
Wada
Kota
K
Kamiya
Masahiro
M
Hayafune
Hanae
H
Kaku
Naoto
N
Shibuya
D017360:Arabidopsis / Q000276:immunology / Q000378:metabolism* / Q000382:microbiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002686:Chitin / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D055786:Gene Knockout Techniques; D012275:Oryza / Q000276:immunology / Q000378:metabolism* / Q000382:microbiology; D010940:Plant Proteins / Q000378:metabolism*; D030821:Plants, Genetically Modified; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism
D029681:Arabidopsis Proteins; C570721:LYM1 protein, Arabidopsis; C580621:LYM2 protein, Arabidopsis; C570722:LYM3 protein, Arabidopsis; D010940:Plant Proteins; D011956:Receptors, Cell Surface; D002686:Chitin; C525882:CERK1 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases