The role of HIG1/MYB51 in the regulation of indolic glucosinolate biosynthesis

Abstract

Glucosinolates are amino-acid derived plant secondary metabolites found mainly in Brassicaceae, including the model plant Arabidopsis thaliana. Due to their role in plant defence and their cancer-preventive properties in human nutrition, they have gained increasing interest over the last years. This study presents the characterisation of the activation-tagging mutant HIG1-1D, which displays a high indolic glucosinolate phenotype, caused by an activation of the R2R3-type MYB transcription factor HIG1/MYB51. A positive correlation between HIG1/MYB51 transcription and the accumulation of indolic glucosinolates could be confirmed in gain and loss-of-function mutants. HIG1/MYB51 expression overlaps with sites of indolic glucosinolate biosynthesis and the expression of biosynthesis genes, which are activated by HIG1/MYB51 in trans. Unlike previously characterised mutants affected in indolic glucosinolate biosynthesis, HIG1-1D displays only minor effects on auxin biosynthesis. However, a role of HIG1/MYB51 in the biotic stress response of A. thaliana appears likely, due to the mechano-sensitive expression of HIG1/MYB51 along with an increased resistance of HIG1-1D plants against a generalist herbivore. Yeast-two-hybrid screening allowed identifying the interaction of HIG1/MYB51 with ATR2/bHLH05, a putative regulator of tryptophan and indolic glucosinolate biosynthesis. Therefore, HIG1/MYB51 appears to be part of a complex network controlling indolic glucosinolate biosynthesis