Characterization of the casbene synthase homolog from Jatropha (Jatropha curcas L.)

The high oil content of Jatropha (Jatropha curcas L.) seeds makes Jatropha an attractive resource for the production of sustainable bioenergy. However, the Jatropha seed kernels also contain antinutrients and various toxins that persist in the oil and seed cakes and pose a safety risk. Since phorbol esters (PEs) are the major contributor to toxicity, a better understanding of PE biosynthesis is expected to elucidate an effective strategy for the utilization of Jatropha plants. In this study, a Jatropha curcas casbene synthase homolog (JcCSH) with high sequence similarity to casbene synthases (CSs) from Ricinus communis, Euphorbia esula, and Sapium sebiferum was cloned from Jatropha leaf tissue. CS has been hypothesized to catalyze the first step of phorbol biosynthesis. JcCSH encodes a protein that contains a chloroplast transit peptide and a DDXXD motif that is conserved among known terpene cyclases. JcCSH was expressed in seedlings, mature leaves, and the flesh of developing fruits, but not in developing seeds. Our results suggest that JcCSH is widely involved in casbene biosynthesis in various tissues other than seeds.