Identification and characterization of (E)-β-caryophyllene synthase and α/β-pinene synthase potentially involved in constitutive and herbivore-induced terpene formation in cotton

Cotton (Gossypium hirsutum L.) plants damaged by insects emit a blend of volatiles, including monoterpenes and sesquiterpenes, which can directly repel herbivores and/or indirectly protect the plant by attracting natural enemies of the herbivores. To understand the molecular basis of terpene biosynthesis and regulation in cotton, two terpene synthase genes, GhTPS1 and GhTPS2, were heterologously expressed and characterized. Recombinant GhTPS1 accepted farnesyl pyrophosphate as substrate and produced (E)-β-caryophyllene and α-humulene. GhTPS2 was characterized as a monoterpene synthase which formed α-pinene and β-pinene using geranyl pyrophosphate as substrate. Quantitative real-time PCR analysis revealed that GhTPS1 and GhTPS2 gene expression was elevated after methyl jasmonate (MeJA) treatment in cotton leaves. Moreover, feeding of the green plant bug Apolygus lucorum, a major cotton pest in northern China, resulted in increased GhTPS2 expression in young leaves, suggesting that GhTPS2 might be involved in plant defense in cotton.