Isolation of a (+)-delta-cadinene synthase gene CAD1-A and analysis of itsexpression pattern in seedlings of Gossypium arboreum L.

The cotton sesquiterpene cyclase, (+)-delta-cadinene synthase,is encoded by a gene family, which can be divided into two subfamilies: CAD1-A and CAD1- C. The gene CAD1-A was isolated from G. arboreum. In situ hybridization per formed on seven-day-old cotton seedlings localized transcripts of both the CAD1-A and CAD1-C mainly in lateral root primordium and apical ground meris tem, vascular tissues of emerging lateral roots, and also in procambium and some subepidermal cells of the hypocotyl. The CAD1-A promoter showed a sim ilar tissue-specificity in transgenic tobacco plants. Histochemistry showed occurrence of sesquiterpene aldehydes in outer cells of the lateral root t ips, as well as in pigment glands. The CAD1 gene expression in G. arboreum seedlings and the spatial pattern of sesquiterpene biosynthesis constitute a chemical defense machinery in cotton seedlings.