Identification Of Chitosan Oligosaccharide Binding Proteins From The Plasma Membrane Of Wheat Cell

Chitosan oligosaccharide(COS),obtained via degradation of deactylated chitin,is a kind of glucosamine oligomers linked by ?-1,4 glycosidic bond with a degree of polymerization from 2 to 8.COS has not only anti-bacterial,anti-viral,anti-fungal activities,but also the ability to improve plant resistance to pests and diseases through stimulating plant immune system.It has been shown that oligosaccharides signals can be recognized and transferred by cell surface receptor proteins of plants in immune mechanism of oligosaccharides.Here,We selected wheat as the sample and utilized fluorescence-labeled COS and quartz crystal microbalance(QCM)to confirm that COSs existed the binding interaction with plasma membrane proteins in wheat protoplast plasma membrane surface.Furthermore,a COS affinity column was used to separate putative COS-binding proteins from wheat plasma membrane proteins.Dextran gel electrophoresis showed that the molecular weight of the COS-binding proteins was between 60 kDa and 90 kDa.HPLC analysis showed that there were more than three typies of proteins in the COS-binding proteins.The COS-binding proteins were further analyzed with LC-MS/MS,and compared with peptide fingerprint database and UniPort protein data bank for identification.Among them,W5G2U8(a potential WAK1 receptor protein),W5HY42 and W5I0R4(potential GsSRK receptor proteins)have been identified.This study showed that COS-binding proteins existed on the plasma membrane surface of wheat cell,and the proteins had the functions of kinase receptor.Bsed on the findings,we hypothesize that the plant immune defense is stimulated by immune signals trasferred to cells via interactions between COS and COS-binding proteins.It is a major step forward to identify the COS-binding proteins from wheat cell and these results will greatly contribute to a better understanding of the plant immune mechanism of COS.