OsMFT2 is involved in the regulation of ABA signaling‐mediated seed germination through interacting with OsbZIP23/66/72 in rice

Seed germination is a complex process involving various physical and biochemical cues, which is determined by exogenous and endogenous factors. Here, we identified a gene, OsMFT2, which negatively regulates seed germination in rice. OsMFT2 knock-out lines exhibited pre-harvest sprouting, while 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 on 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 ABA responsive element containing gene, and OsMFT2 enhanced their binding activities to Rab16A promoter. Moreover, several ABA responsive genes were differentially expressed in the imbibed seeds of OsMFT2 transgenic lines and wild-type. Performance of transgenic plants demonstrated that overexpressing OsbZIP23 rescued the pre-harvest sprouting phenotype and expression decrease of ABA signaling genes caused by OsMFT2 knocking-out. All these results demonstrated that OsMFT2 positively regulates ABA response genes through interacting with OsbZIP23/66/72 and functions in seed germination.