*2.6. OsbHLH079 Might Indirectly Regulate Expressions of OsBZR1, and ILI1*

As OsBZR1 directly regulates the expression of *ILI1*, and *DLT* [23], it is possible that (1) OsbHLH079 modulates the expression and/or activity of OsBZR1, (2) OsbHLH079 directly regulates other genes because OsBZR1 has a limited function, in which the effect of overexpressed OsBZR1 occurs only when the binding site of negative regulators, such as 14-3-3 or GSK2, is mutated in plants [23,63,76], or (3) OsbHLH079 directly regulates downstream genes of *OsBZR1*, such as *ILI1*, and *DLT*, and expression of *OsBZR1* is increased by a feedback regulatory loop.

To examine the possible roles of OsbHLH079 in the transcription of *OsBZR1*, *ILI1*, and *DLT* in rice, we investigated the promoter sequences of *OsBZR1*, *ILI1*, and *DLT* (−2000 to −1 from the ATG). It revealed that *OsBZR1* or *ILI1* did not contain the G-box sequence (CACGTG; a putative binding site of bHLH-type transcription factors), but only one CACGTG sequence in the promoter region (-989 to −984 from ATG) of *DLT*. These findings suggest that OsbHLH079 regulates *OsBZR1* and *ILI1* indirectly, although we cannot exclude the possibility that OsbHLH079 binds to the promoter regions of *OsBZR1* and *ILI1*.
