Two Myb genes synergically control aliphatic glucosinolate metabolism in Arabidopsis

Coregulation analysis of Arabidopsis microarray data suggests Myb28 and Myb29 as potential regulators of aliphatic Glucosinolate (GLS) metabolism. We isolated two insertional mutants for Myb28 and one for Myb29. All mutants have a normal growth phenotype, but the myb28 mutants are defective in the activation of several of the coregulated genes (MAM1, MAML, BCAT4 and two putative Aconitases) involved in aliphatic GLS synthesis, as judged by normal and qPCR. Reduction was between 2 and 10 fold, depending on the gene. Metabolome analysis proved that indeed long chain (but not short chain) aliphatic GLS are missing in the myb28 KO. A double myb28myb29 mutant showed complete loss of expression of genes in the aliphatic branch and contains no aliphatic GLS. Other single and double mutants in other genes of the same Myb subfamily are being isolated. Promoters of the genes coregulated with Myb28 were analyzed for common elements. One G-Box (known to regulate expression of photosynthetic genes) and an 8 bp novel conserved motif were both identified in almost all promoters. The second element could mediate MYB28 (and/or MYB29) binding. Attempts to express and purify MYB28 are underway