抄録
When plants are attacked by pathogenic microorganisms, they respond with a variety of defense reactions including production of phytoalexins. Recently, we found that five enzyme genes (OsCPS4, OsKSL4, CYP99A2, CYP99A3, and OsMAS) that are involved in biosynthesis of diterpenoid phytoalexins, momilactones, form a gene cluster on rice chromosome 4. These enzyme genes are co-ordinately induced in cultured-cells by chitin oligosaccharade elicitor treatment. To elucidate regulatory mechanisms for the co-ordinate expression of the genes, we first performed promoter analysis of OsKSL4, resulting in identification of OsTGA1 as a bZIP-type transcription factor that directly regulates the elicitor-inducible expression of OsKSL4. We also found that expression of all the cluster members was greatly reduced in the ostga1 mutant lines, and that expression of all the cluster members was greatly enhanced in the OsTGA1 overexpressing lines. These results suggest that OsTGA1 is a master transcription factor regulating expression of the mmomilactone biosynthetic gene cluster. Investigation of the mechanisms by which OsTGA1 co-ordinately regulates expression of all the cluster members is now under way.
