Functional characterization of (E)-β-caryophyllene synthase from lima bean and its up-regulation by spider mites and alamethicin

(E)-β-Caryophyllene is a sesquiterpene compound widely distributed in plants and functions in plant defence. However, little is known about the sequence and function of (E)-β-caryophyllene synthase in lima bean (Phaseolus lunatus). Here, we report a new full-length cDNA (PlCAHS) encoding (E)-β-caryophyllene synthase, a possible key enzyme of plant defence. The cDNA of PlCAHS contains an open reading frame of 1 761 bp, encoding a protein of 586 amino acids with a predicted mass of 67.95 kDa. The deduced amino acid sequence shows 52% identity with sesquiterpene synthase MtCAHS of Medicago truncatula. Based on phylogenetic analysis, PlCAHS is classified as the terpene synthases (TPS)-a subfamily. The recombinant enzyme, expressed in Escherichia coli, catalysed the formation of a major product (E)-β-caryophyllene (82%) and a minor product α-humulene (18%) from farnesyl diphosphate. Real-time quantitative PCR (qRT-PCR) analysis found that the PlCAHS transcript was significantly up-regulated in leaves after treatment with spider mites and alamethicin (ALA), suggesting its ecological function in plant defence.