The characterization of transgenic rice plants expressing a pepper 5-epi aristolochene synthase, the first committed step enzyme for capsidiol synthesis in isoprenoid pathway

Abstract 5- Epi -aristolochene synthase (EAS) from Capsicum annuum was introduced into the rice genome under the control of a maize ubiquitin promoter by Agrobacterium -mediated transformation. Fifteen independent transgenic rice plants were isolated and characterized. The integration and expression of the transgene were verified through the use of Southern, Northern, and Western blot analyses. The heterologous expression of EAS in transgenic rice did not interfere with the activities of endogenous squalene synthase (SS) or farnesyl diphosphatase (FDPase), in which both enzymes used the same substrate-farnesyl diphosphate (FDP), for the production of squalene and farnesol, respectively. Transgenic rice cells exhibited the induction of EAS enzyme activity upon elicitor ( N -acetylchitohexaose) and jasmonic acid (JA) treatments. The induction of EAS enzyme activity was accompanied by an increase in EAS mRNA when challenged by the elicitor. Results indicated that the maize ubiquitin promoter was upregulated upon jasmonic acid and elicitor treatments. Results also show that the EAS ectopic expression in transgenic rice plants resulted in the synthesis of 5- epi -aristolochene in vivo upon elicitor treatment, suggesting that the heterologous expression of pepper EAS is coupled with the endogenous biosynthetic pathway channel of isoprenoid in rice cells.