1206 Sesqui- and Sesterterpenoids of Cotton: Biosynthesis and Function

Cotton produces a diverse mixture of sesquiterpenoids and sesterterpenoids that protect the plant from pathogens and insects. These compounds may be preformed and/or induced by pathogen attack or insect herbivory. The preformed compounds occur in subepidermal lysigenous glands, while the pathogen-induced compounds are synthesized by specialized cells such as paravascular cells appressed to xylem vessels infected by fungal pathogens or in palisade or mesophyll cells adjacent to infection sites on leaves. Some of the genes involved in the biosynthesis of these compounds have been identified and the structures of several biosynthetic intermediates have been elucidated. The structures, occurrence, biological activity toward fungal pathogens and insects, and biosynthesis of these compounds are the subjects of this paper.