Anthocyanin biosynthesis is regulated by
regulatory genes encoding transcription factors
which control expression of several structural genes
in the anthocyanin pathway. The OSB2 gene
encoding a Myc-type basic-helix-loop-helix (bHLH)
transcription factor which regulates anthocyanin
biosynthesis was previously cloned from a Thai
black rice variety Khum. In this study, the cloned
OSB2 gene was transformed into two white rice
varieties Nipponbare and Taichung 65 using
Agrobacterium to study the regulation of anthocyanin
biosynthesis in rice. The semi-quantitative RT-PCR
analysis revealed that transgenic rice plants
overexpressing the OSB2 gene up-regulated the
expression of some structural genes in anthocyanin
biosynthesis including early biosynthesis gene (EBG)
i.e. F3H (flavanone 3-hydroxylase) and also late
biosynthesis genes (LBGs) i.e. DFR (dihydroflavonol
4-reductase) and ANS (anthocyanidin synthase). The
present results support the other evidences that the
regulatory mechanism of anthocyanin biosynthesis in
rice may be different from other plants in which
EBGs and LBGs were regulated separately. The
results provide the understanding of functions of
OSB2 gene in regulation of anthocyanin biosynthesis
pathway in rice and will be useful to apply this gene
as a marker gene for the improvement of rice
varieties.