Functional Analysis Of Rice Class Ⅲ Peroxidases Genes OsPER2 And OsPER4 In Cell Wall Synthesis

Class Ⅲ peroxidases are common oxidoreductases in plants.They have many important functions,such as cell growth,cell wall modification,lignin synthesis,stress resistance and so on.The class Ⅲ peroxidase gene family contains many members.Systematic analysis of the biological information of these genes is of great significance to reveal the gene function of the family.In this study,139 class Ⅲ peroxidase genes were identified from rice.The evolutionary relationship,chromosome location,protein physicochemical properties,conserved motifs,gene structure and cis acting elements of these genes were analyzed by means of bioinformatics.On this basis,RNAi materials of LOC_Os05g04500.1(OsPER2)and LOC_Os01g19020.1(OsPER4)members of C subfamily of rice class Ⅲ peroxidase gene family were constructed by transgenic technology,and the field phenotype,stress tolerance and cell wall composition of RNAi materials were analyzed,so as to preliminarily reveal the function of class Ⅲ peroxidase.The main results are as follows.1.Bioinformatics analysis showed that there were 139 members of rice class Ⅲperoxidase gene family,which were divided into three groups:A,B and C,with corresponding numbers of 5,54 and 80,respectively;chromosomal mapping results showed that chrl and chr7 had 24 genes,while chr8 had the least,with only three genes;the protein physicochemical properties showed that the amino acid sequences of 139 rice class Ⅲ peroxidase family genes ranged from 244 to 1367,the molecular weight of protein ranged from 27.02 kDa to 146.65 kDa,and the isoelectric point ranged from 4.17 to 9.64;the number of exons in each gene structure was different,89.9%of the members had 2-4 exons;91.4%of the members had 9-10 conserved motifs;promoter analysis showed that rice class Ⅲ peroxidase gene might be activated under drought,low temperature and other stresses,thus playing its role in plant protection.Bioinformatics analysis also showed that both OsPER2 and OsPER4 were members of group C of the class Ⅲ peroxidase gene family.Prediction of subcellular localization showed that both of them were located in the cytoplasm and the conserved motifs of proteins were very similar.2.The phenotypes of OsPER2 and OsPER4 RNAi plants were investigated.Compared to wild type,OsPER2 transgenic lines showed higher plant height,seed setting rate and 1000 grain weight.The biomass per plant of the transgenic lines increased,the lodging resistance and the breaking force decreased significantly.OsPER4 transgenic lines showed higher plant height,increased tiller number,seed length and width,but decreased seed setting rate and 1000 grain weight.Moreover,the biomass per plant of OsPER4 transgenic materials increased,lodging resistance and breaking force decreased significantly.3.Based on the microarray data GSE6901 of 7-day-old seedlings of indica rice IR64 under different stress treatments,the expression of OsPER2 and OsPER4 genes on plants under different stress treatments were explored.The results showed that the expression of OsPER2 and OsPER4 decreased significantly in 7-day-old seedlings of indica rice ir64 under 200 mM NaCl stress for 3 hours.We also found that the survival rate of NPB in 10-day-old rice seedlings treated with 100 mM NaCl for 15 days was significantly lower than that of OsPER2 and OsPER4 transgenic materials.4.The cell wall composition of OsPER2 and OsPER4 transgenic materials was determined,compared with NPB,the cellulose content of OsPER2-1 and OsPER2-2 increased by 13.7%and 15.9%respectively,hemicellulose content decreased by 12.6%and 15.4%respectively,and lignin content decreased by 4.0%and 5.5%respectively.Similarly,trend was found in OsPER4.Compared with NPB,the cellulose content of OsPER4-1,OsPER4-2 and OsPER4-3 increased by 18.6%,22.6%and 21.7%respectively,the hemicellulose content decreased by 13.5%,13.2%and 21.8%respectively,and the lignin content decreased by 7.7%,8.1%and 14.5%respectively.5.This study laid a solid foundation for further study on the function of class Ⅲperoxidases genes in cell wall biosynthesis,provided strong evidence for subsequent research,and also provided potential gene resources for genetic improvement of rice cell wall.