Cloning and prokaryotic expression of rice gene encoding β-caryophyllene synthase and its genetic transformation.

To elucidate the role of β-caryophyllene emitted from rice plants in mediating interactions among rice,herbivores and their natural enemies,a rice β-caryophyllene synthase gene OsCAS was cloned,expressed in E.coli and over-expressed or silenced in rice plants using an Agrobacterium-based transformation system.The gene OsCAS,a 1731 bp cDNA,contains an open reading frame of 1728 bp,which encodes a protein of 576 amino acids with a calculated molecular weight of 66.5 kDa.Phylogenetic tree analysis showed that the putative rice OsCAS had a high amino acid identity(99%) to maize(Zea mays) β-caryophyllene synthase,whereas a low amino acid identity(51%) to those in other plants including Arabodopsis(Arabidopsis thaliana),Artemisia(Artemisia annua) and cucumber(Cucumis sativus).Infestation by rice brown planthopper Nilaparvata lugens(Stl) or jasmonic acid treatment enhanced significantly the expression levels of OsCAS gene.The recombinant OsCAS protein was expressed in E.coli and rice lines with over-expression or RNAi silencing of OsCAS gene were obtained by Agrobacterium-mediated transformation,which laid a foundation for elucidating the biochemical and ecological functions of OsCAS.