Abstract
Plant chemical defense mechanisms have been systematically investigated using a model plant species, Arabidopsis, synthesizing camalexin, indolic glucosinolates (iGS), and aliphatic glucosinolates (aGS) as major defense compounds. Here, we report a novel transcription factor gene (camalexin deficient; CMD) involved in the fine-tuning of the biosynthetic pathways of camalexin and GS in Arabidopsis. Plants carrying T-DNA insertion events within the CMD gene (cmd plants) failed to respond to the treatments of camalexin induction. Expression of CYP71A12, a camalexin biosynthesis gene, was found to be reduced in the roots of cmd plants, while CMD-overexpressing plants accumulated CYP71A12 transcripts at constantly higher levels, suggesting that the defect in camalexin biosynthesis in the cmd line could be ascribed to the insufficient CYP71A12 expression. Besides camalexin biosynthesis, the cmd line was characterized by altered profiles of both iGS and aGS, as well as the transcription factor genes regulating biosyntheses of iGS (MYB51, MYB122, MYB34) and aGS (MYB28, MYB29), implicating the possibility that CMD may control a total balance of secondary metabolic pathways in Arabidopsis.
