The MYB transcription factors play important roles in the regulation of many secondary metabolites at the transcriptional level. We evaluated the possible roles of the Arabidopsis R2R3-MYB transcription factor genes in flavonoid biosynthesis as they are induced by UV-B irradiation but are largely unexplored in terms of their associated phenotypes. We found that one member of this gene family, AtMYB60, inhibits anthocyanin biosynthesis in the lettuce plant. Wild type lettuce normally accumulates anthocyanin, predominantly cyanidin and traces of delphinidin, and develops a red pigmentation. However, the accumulation of anthocyanin pigments in AtMYB60 overexpressing lettuce was inhibited. We further found a complete absence of DFR transcripts in AtMYB60 overexpressing lettuce, whereas other biosynthetic genes in the anthocyanin metabolism pathway were expressed. To provide genetic tools the regulation of seed color of rapeseed which has been target for fuel, AtMYB was overexpressed in rapeseed. Transgenic plants showed lighter seed color and improved tolerance to abiotic stress than the wild type plants. The elucidation of the roles of the AtMYB60 transcription factor will facilitate further studies and provide genetic tools to better understand the regulation in plants of the genes controlled by the MYB-type transcription factors.

• Jong-Sug Park(Molecular Physiology and Biochemistry Division, National Institute of Agricultural Biotechnology)