BANYULS, A NOVEL NEGATIVE REGULATOR OF FLAVONOID BIOSYNTHESIS IN THE ARABIDOPSIS SEED COAT

A mutant of Arabidopsis that accumulates a high level of red pigments within the seed coat has been isolated from a population of T-DNA-tran sformed plants. Genetic analysis revealed that the mutation is recessi ve and affects maternal seed tissues only. Due to the color of the imm ature seeds, this mutation was named banyuls (ban). Pigments accumulat ed continuously from early seed development to the desiccation stage i n the seed coat of the mutant. The phenotype of the double mutant bany uls/transparent testa confirmed the flavonoid nature of the pigments a nd enabled assignment of the regulatory TT (Transparent Testa) genes t o two groups according to their epistatic relationship to ban. The fla vonoid content of germinated ban and wild-type seedlings was similar. Plants harbouring the ban mutation had a normal formation of trichomes and root hairs and were not affected in their responses to light. The seeds of ban plants exhibited reduced germination compared to wild-ty pe which may be a direct consequence of the high level of pigments. Th ese results suggest that BANYULS functions as a negative regulator of flavonoid biosynthesis that prevents accumulation of pigments in the s eed coat during early embryogenesis in Arabidopsis.