Novel Insights Into the Function of Arabidopsis R2R3-MYB Transcription Factors Regulating Aliphatic Glucosinolate

MYB76, positively regulate aliphatic glucosinolate (AGSL) biosynthesis. Mutual transcriptional regulation among theseMYB genes makes it difficult to elucidate their individ-ual function simply by analyzing knock-out mutants or ecto-pically overexpressing lines of these genes. In this study, we constructed transgenic lines expressing each MYB gene driven by its own promoter in themyb28myb29 background, where the expression of the endogenousMYB28,MYB29 and MYB76 was repressed with no AGSL accumulation. In leaves, transgenic MYB28 expression activated AGSL biosynthetic genes and restored accumulation of AGSLs with short side chains. TransgenicMYB29 expression activated the same bio-synthetic pathway, but induction of the genes involved in side chain elongation was weaker than that by MYB28, re-sulting in a weaker recovery of AGSLs. Neither MYB28 no