Gene Cloning And Function Analysis Of Rice Brittle Culm Mutant OsC116

Plant secondary cell wall,a major biomass resource,is a rigid and dynamic network system comprising polysaccharides,aromatic substances and glycoproteins.It fundamentally determines plant mechanical strength and also plays roles in plant growth and development.Rice is a major food crops over the world with enormous biomass residues for biofuels.Therefore,it is important to understand the secondary cell wall biosynthesis in rice.In this study,we selected a rice brittle culm mutant named Os C116,generated from EMS mutagenesis of rice cultivar(ZH11).By crossing with MH63 and 9311 respectively,two mapping population PB1(C116 / MH63)and PB2(C116 / 9311)were obtained.A down 132-kb region containing 9 open reading frame(ORF)was mapped and mutation site was identified using map-based cloning approach.The main results are as follows:1.The Os C116 mutant gene,Os05g07790,encoded a glycosyl transferase(GTs)protein,which belongs to the transmembrane protein.2.Compared with wild type(ZH11),the mutant(Os C116)exhibited brittle phenotypes at booting stage,leading to a reduced stretching resistance and increased breaking strength.The mature mutant plant also showed a reduced plant height and tiller number by 14.8% and 18.0%,respectively.Notably,the mutant exhibited a significantly enhanced lodging resistance.3.The mutant showed no difference in panicle length,grain character,1000-grain weight compared with wild type.But it had an increase in the brown rice rate and milled rice rate,especially the chalkiness which determines the quality of rice.Hence,the mutant had high quality of grains compared with wild type.4.Cell wall compositon analysis indicated that the Os C116 mutant had a reduced cellulose level and increased content.In terms of wall polymer features,lignocellulose crystallinity(Cr I)was significantly reduced in the mutant.Notably,arabinose,glucose and xylose were increased in the hemicellulosic compositions of mutant.In addition,the mutant exhibited an increase either in acid-insoluble lignin by20.3% or in G and S proportions,compared with wild type.5.Pretreated with three concentrations of Na OH(0.5%,1%,and 4%)or H2SO4(0.5%,1%,and 2%),the mutant showed a reduced hexose yield.By comparison,the mutant showed an increased total sugar yield from from 0.5% and 4% Na OH pretreatments.6.Treated with 200 μM Cd for 4 days,the mutant showed less tolerance to Cd than that of wild type.7.Genetic complementation experiments confirmed that the mutant(Os C116)phenotypes were restored as wild type.