| dc.description.abstract | During rice germination, α-amylase genes are controlled by sugar and gibberellins (GAs). The cis-eletment, TA box (TATCCA), has been identified and showed that it plays an important role both in sugar- and in GA-regulated α-amylase gene expression. In our previous study, TA box binding factors, OsMYBS1, OsMYBS2, and OsMYBS3, were identified. Transient expression assay showed that OsMYBS2 recognized TA box specially and functioned as a repressor. Previous studies have shown that the barley HvMCB1 is the orthologous gene of OsMYBS2 and the N-terminal (residues 1-41) of HvMCB1 is essential for negative regulation of α-amylase.
In this study, we showed that the N-terminal (residue 1-53) of OsMYBS2 is not essential for the repression of α-amylase by transient assay. Transgenic rice overexpressing OsMYBS2(tr) (N-terminal truncated version of OsMYBS2) shown that OsMYBS2(tr) is a repressor of α-amylase gene. Compared to wild-type, overexpression of OsMYBS2(tr) caused α-amylase gene hypersensitive to sugar repression, whereas RNAi of OsMYBS2 slowed down the sugar repression response. Although sugar starvation slightly decreased OsMYBS2 mRNA, protein level of OsMYBS2(tr) was much less, implying that OsMYBS2(tr) was regulated post-transcriptionally. Seed germination assay indicated that germination rate was delayed in OsMYBS2(tr) overexpression plants. Taken together, it shows that OsMYBS2 plays a role in regulating seed germination and seeding growth in rice. | en_US |