Phytochrome-regulated EBL1 contributes to ACO1 upregulation in rice

The 1-aminocyclopropane-1-carboxylate oxidase gene (ACO1) was upregulated in rice (Oryza sativa L.) phyAphyBphyC mutants lacking any phytochrome and containing the GCC box element, a binding site for rice ethylene-responsive element binding protein 1 (OsEREBP1), in its promoter region. Since the OsEREBP1-like gene EBL1 (OsEREBP1-LIKE 1) was significantly downregulated in phyAphyBphyC mutants, EBL1 was suspected to repress ACO1 expression in wild-type plants. However, ACO1 was downregulated in EBL1 RNA interference plants, and the total length of these plants was slightly shorter than that of wild-type plants. This study shows that EBL1 is positively regulated by phytochrome B and associated with ACO1 upregulation.