No abstract

Summary Seed germination is a complex process involving various physical and biochemical cues, determined by exogenous and endogenous factors. Here, we identified a gene, OsMFT2, that negatively regulates seed germination in rice. OsMFT2 knock‐out lines exhibited pre‐harvest sprouting, whereas OsMFT2 overexpression lines showed delayed germination. RNA expression profiling showed that OsMFT2 was specifically expressed in seeds. Subcellular localization indicated that OsMFT2 was a nuclear protein. Exogenous abscisic acid (ABA) treatment of imbibed seeds and seedlings indicated that OsMFT2 altered ABA sensitivity during seed germination and post‐germination growth. In vivo and in vitro assays showed that three bZIP transcription factors, OsbZIP23, OsbZIP66 and OsbZIP72, interacted with OsMFT2. OsbZIP23/66/72 bound to the promoter of Rab16A, a typical gene containing the ABA‐responsive element, and OsMFT2 enhanced the binding to the Rab16A promoter. Moreover, several ABA‐responsive genes were differentially expressed in the imbibed seeds of OsMFT2 transgenic lines and the wild type. The performance of the transgenic plants demonstrated that overexpressing OsbZIP23 rescued the pre‐harvest sprouting phenotype and the decrease in ABA‐signaling genes expression caused by OsMFT2 knock‐out. All of these results demonstrate that OsMFT2 positively regulates ABA‐responsive genes through interacting with OsbZIP23/66/72 and functions in seed germination.

A new rice gene, OsMFT1, was identified that both regulates rice heading date and panicle architecture and is different from its homologs in other species.