Expression analysis of anthocyanin regulatory genes in response to different light qualities in Arabidopsis thaliana

In this work we analysed, at the transcript level, the response of Arabidopsis anthocyanin regulatory genes of the MYB (PAP1 and PAP2), bHLH (TT8, EGL3 and GL3) and WD40 (TTG1) families to white tight in seedlings and to different light qualities in rosette leaves. Our experiments showed strong tight induction of the MYB genes PAPI and PAP2. In particular, the kinetics of PAP1 expression preceded those of PAP2 and all. of the structural genes (CHS, DFR, F3H, LDOX), consistent with the hypothesis that it has a key role in Light induction of anthocyanin biosynthesis. All bHLH genes analysed showed tight induction, and in seedlings their expression preceded that of the late structural genes, suggesting their possible rote in light regulation of these structural genes. TFG1 expression is essentially constitutive in both systems. Experiments with transgenic tines over-expressing the MYB factors show that PAP1, but not PAP2, strongly stimulates expression of the anthocyanin structural gene encoding dihydroflavonol reductase, but neither factor affected expression of the early flavonoid biosynthesis gene encoding chalcone synthase. Consistent with these findings, PAP1, but not PAP2, stimulated tight induction of anthocyanin biosynthesis in seedlings. We conclude that specific members of the MYB and bHLH families play important rotes in regulating anthocyanin biosynthesis in response to different light qualities in Arabidopsis. (C) 2007 Elsevier GmbH. All rights reserved.