Functional Analysis Of SGT2,CDPK32 And CesA8 Genes In Cotton

Cotton is a major economic crop and its fibers have important application in textile industry.Because cotton fibers contain more than 95% cellulose,cellulose biosynthesis and accumulation directly affect quality of cotton fibers.Cellulose synthase complexes(CSC)are composed of a variety of cellulose synthase(CesA)and its binding proteins.The SGT2,CDPK32 and CesA8 genes have been identified for cellulose synthesis in cotton.In particular,the SGT2 and CesA8 genes may be involved in the cellulose synthesis of cotton fiber secondary walls,whereas the CDPK32 may act as a binding protein for CSC formation and regulation.However,much remains unknown about SGT2,CDPK32 and CesA8 roles in plant growth and development.In this paper,Arabidopsis thaliana and cotton were used to study functions of GhSGT2,GhCDPK32 and GhCesA8 genes.The main results are described below:1.Heterologous expression of GhSGT2 in Arabidopsis thaliana,the plant height of GhSGT2 transgenic lines increased significantly,and the growth rate of OE-8 and OE-10 strains exceeded 12%;seedling growth period was advanced,root length elongation,the length of which increased by more than 28%.At the same time,the cell wall thickness of the vascular bundle lignocellus of the transgenic plants increased significantly,mainly due to increased thickness of secondary cell walls by 32%.Based on chemical analysis,the transgenic lines contained significantly increased levels of cellulose,pectin and soluble sugars,but had the reduced hemicellulose content.In addition,the transgenic lines showed relatively higher abiotic stress resistance than that of the wild type(WT).2.Heterologous expression of GhCDPK32 in Arabidopsis thaliana,the GhCDPK32 transgenic lines showed much enhanced plant growth including increased plant height by12%-15% and seedling root length by more than 47%.However,the cell wall thickness of the transgenic Arabidopsis vascular bundle cells was significantly reduced with the primary wall thickness decreased by 24% and the secondary wall thickness decreased by34%.Furthermore,the transgenic lines contained significantly increased pectin and soluble sugars,but had much reduced cellulose,hemicellulose and lignin.The transgenic lines also exhibited higher abiotic stress resistance relative to the WT.3.Heterologous expression of GhCesA8 in Arabidopsis thaliana,the GhCesA8 transgenic lines did not show any significantly different phenotypes in transgenic lines including plant growth and stress responses.However,the primary cell wall thickness and secondary wall thickness of the transgenic Arabidopsis vascular bundle cells was significantly reduced.Analysis of the main components of the cell wall revealed that the hemicellulose content of the transgenic lines was significantly reduced.4.SGT2,CDPK32 and CesA8 genes are mainly expressed in the fibers 20-30 days after flowering,which were suggested to involve in the synthesis of secondary cell wall of cotton fibers.The CDPK32 gene was also high expressed in the fiber 10 days after flowering,which may be involved in the initial fiber development.The SGT2,CDPK32 and CesA8 genes showed significantly expression pattern in upland cotton and island cotton seedlings.SGT2 and CesA8 were mainly expressed in leaves,and its expression level in upland cotton was higher than that of island cotton.6.Co-IP analysis suggested that CesA8 protein may interact with SGT2 and CDPK32,But it remained to determine SGT2 and CDPK32 interaction in the future.