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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.

As a major component of ideal plant architecture, leaf angle especially flag leaf angle (FLA) makes a large contribution to grain yield in rice. We utilized a worldwide germplasm collection to elucidate the genetic basis of FLA that would be helpful for molecular design breeding in rice. Genome-wide association studies (GWAS) identified a total of 40 and 32 QTLs for FLA in Wuhan and Hainan, respectively. Eight QTLs were commonly detected in both conditions. Of these, 2 and 3 QTLs were identified in the indica and japonica subpopulations, respectively. In addition, the candidates of 5 FLA QTLs were verified by haplotype-level association analysis. These results indicate diverse genetic bases for FLA between the indica and japonica subpopulations. Three candidates, OsbHLH153, OsbHLH173 and OsbHLH174, quickly responded to BR and IAA involved in plant architecture except for OsbHLH173, whose expression level was too low to be detected; their overexpression in plants increased rice leaf angle. Together with previous studies, it was concluded that all 6 members in bHLH subfamily 16 had the conserved function in regulating FLA in rice. A comparison with our previous GWAS for tiller angle (TA) showed only one QTL had pleiotropic effects on FLA and TA, which explained low similarity of the genetic basis between FLA and TA. An ideal plant architecture is expected to be efficiently developed by combining favorable alleles for FLA from indica with favorable alleles for TA from japonica by inter-subspecies hybridization.

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Heading date is an important agronomic trait of rice (Oryza sativa L.) and is regulated by numerous genes, some of which exhibit functional divergence in a genetic background-dependent manner. Here, we identified a late heading date 7 (lhd7) mutant that flowered later than wild-type Zhonghua 11 (ZH11) under natural long-day (NLD) conditions. Map-based cloning facilitated by the MutMap strategy revealed that LHD7 was on the same locus as OsPRR37 but exhibited a novel function as a promoter of heading date. A single-nucleotide mutation of G-to-A in the coding region caused a substitution of aspartic acid for glycine at site 159 within the pseudo-receiver (PR) domain of OsPRR37. Transcriptional analysis revealed that OsPRR37 suppressed Ghd7 expression in both ZH11 background under NLD conditions and the Zhenshan 97 background under natural short-day conditions. Consistently, the expression of Ehd1, Hd3a and RFT1 was enhanced by OsPRR37 in the ZH11 background. Genetic analysis indicated that the promotion of heading date and reduction in grain yield by OsPRR37 were partially dependent on Ghd7. Further investigation showed that the alternative function of OsPRR37 required an intact Ghd7-related regulatory pathway involving not only its upstream regulators OsGI and PhyB but also its interacting partner Hd1. Our study revealed the distinct role of OsPRR37 in the ZH11 background, which provides a more comprehensive understanding of OsPRR37 function and enriches the theoretical bases for improvement of rice heading date in the future.