Abstract
The production of phytoalexin momilactones, plant defense-related diterpenoid compounds, is induced in rice upon recognition of pathogenic invasion. The momilactone biosynthetic genes (OsCPS4, OsKSL4, CYP99A2, CYP99A3, and OsMAS) are clustered on chromosome 4 and are coexpressed after elicitation that mimics pathogen attack.
To elucidate regulatory mechanisms for the coordinate expression of the genes, we first performed promoter analysis of OsKSL4, and identified that a bZIP-type transcription factor is involved in the OsKSL4 gene expression. OsTGAP, which was screened by microarray analysis under elicitation, was identified as a bZIP-type transcription factor that directly regulates the elicitor-inducible expression of OsKSL4. We also found that the expression of five clustered genes was hardly detected in the ostgap mutant, and was strongly enhanced in the OsTGAP overexpressing lines. These results indicated that the OsTGAP is a master transcription factor regulating expression of the momilactone biosynthetic gene cluster.
