Promoter analysis of the rice stemar-13-ene synthase gene OsDTC2, which is involved in the biosynthesis of the phytoalexin oryzalexin S.

A rice diterpene cyclase, OsDTC2, functions as a stemar-13-ene synthase that converts syn-copalyl diphosphate into stemar-13-ene, a putative diterpene hydrocarbon precursor of the phytoalexin oryzalexin S. The transcriptional expression of OsDTC2 is induced by treatment of suspension-cultured rice cells with a chitin oligosaccharide elicitor. To investigate the molecular mechanisms of the elicitor signaling pathway that leads to OsDTC2 expression, we carried out deletion and mutation analysis of the region -1939 bp upstream of the transcription start site of OsDTC2 in rice cells using dual luciferase assays. The region between -1709 and -1450 bp was found to contain six W-box motifs, which are putative recognition sites for WRKY transcription factors, as cis elements involved in elicitor-responsiveness and/or basic promoter activity of OsDTC2.