Cloning and expression analysis of OCPI2 gene in rice

To investigate the function of protease inhibitor genes in rice defense against herbivorous insects, the coding sequence of the protease gene OCPI2 from the rice variety ‘Zhonghua 11' was cloned. The sequence characteristics of OCPI2 gene were analyzed, and a phylogenetic tree was constructed using bioinformatics software. Real-time quantitative PCR was utilized to examine the expression characteristics of OCPI2 gene under herbivorous insect feeding and plant hormone treatment. The results were as follows:(1)The coding region of OCPI2 gene was 219 bp, encoding a protein of 72 amino acids. The OCPI2 protein had a molecular weight of 7.72 kDa and a theoretical isoelectric point of 5.21, with no signal peptide and no transmembrane structure.(2)The OCPI2 protein was closely related to the homologous protein in Triticum urartu(EMS61613.1).(3)The OCPI2 gene contained a potato_inhibit conserved domain and belonged to the serine protease inhibitor family.(4)The expression of OCPI2 gene was induced by feeding from the rice striped stem borer(Chilo suppressalis)and the brown planthopper(Nilaparvata lugens), mechanical damage, and methyl salicylate treatment, whereas methyl jasmonate treatment consistently suppressed OCPI2 gene expression. Taken together, these results suggest that OCPI2 gene may be involved in the induced defense response of rice to herbivorous insects. This study provides a theoretical basis for a deeper understanding of the function of OCPI2 gene in rice defense against insect herbivores.