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Soil salinity has a major impact on rice seed germination, severely limiting rice production. Herein, a rice germination defective mutant under salt stress (gdss) was identified by using chemical mutagenesis. The GDSS gene was detected via MutMap and shown to encode potassium transporter OsHAK9. Phenotypic analysis of complementation and mutant lines demonstrated that OsHAK9 was an essential regulator responsible for seed germination under salt stress. OsHAK9 is highly expressed in germinating seed embryos. Ion contents and non‐invasive micro‐test technology results showed that OsHAK9 restricted K+ efflux in salt‐exposed germinating seeds for the balance of K+/Na+. Disruption of OsHAK9 significantly reduced gibberellin 4 (GA4) levels, and the germination defective phenotype of oshak9a was partly rescued by exogenous GA3 treatment under salt stress. RNA sequencing (RNA‐seq) and real‐time quantitative polymerase chain reaction analysis demonstrated that the disruption of OsHAK9 improved the GA‐deactivated gene OsGA2ox7 expression in germinating seeds under salt stress, and the expression of OsGA2ox7 was significantly inhibited by salt stress. Null mutants of OsGA2ox7 created using clustered, regularly interspaced, short palindromic repeat (CRISPR)/CRISPR‐associated nuclease 9 approach displayed a dramatically increased seed germination ability under salt stress. Overall, our results highlight that OsHAK9 regulates seed germination performance under salt stress involving preventing GA degradation by mediating OsGA2ox7, which provides a novel clue about the relationship between GA and OsHAKs in rice. [ABSTRACT FROM AUTHOR]

Seed germination plays a pivotal role in the plant life cycle, and its precise regulatory mechanisms are not clear. In this study, 19 quantitative trait loci (QTLs) associated with rice seed germination were identified through genome-wide association studies (GWAS) of the following traits in 2016 and 2017: germination rate (GR) at 3, 5, and 7 days after imbibition (DAI) and germination index (GI). Two major stable QTLs, qSG4 and qSG11.1 , were found to be associated with GR and GI over 2 continuous years. Furthermore, OsPK5 , encoding a pyruvate kinase, was shown to be a crucial regulator of seed germination in rice, and might be a causal gene of the key QTL qSG11.1 , on chromosome 11. Natural variation in OsPK5 function altered the activity of pyruvate kinase. The disruption of OsPK5 function resulted in slow germination and seedling growth during seed germination, blocked glycolytic metabolism, caused glucose accumulation, decreased energy levels, and affected the GA/ABA balance. Taken together, our results provide novel insights into the roles of OsPK5 in seed germination, and facilitate its application in rice breeding to improve seed vigour. [ABSTRACT FROM AUTHOR]

The C2H2-type zinc finger proteins (ZFPs) are involved in a wide range of plant development and stress responses. Many studies have shown the positive roles of ZFP genes in stress tolerance. However, overexpression of ZFP genes usually leads to the side effect of growth retardation. Here we report a new member of the ZFP family, Oryza sativa drought-responsive zinc finger protein 1 (OsDRZ1), positively regulating both stress tolerance and plant architecture in rice (Oryza sativa L.). OsDRZ1 was expressed throughout all tissues examined and could be induced by multiple abiotic stresses. OsDRZ1 protein was localized mostly in the nucleus. Unlike most reported rice ZFPs functioning as transcriptional activators, OsDRZ1 is a transcriptional repressor. Overexpression of OsDRZ1 in rice increased seedling drought tolerance and the transgenic plants appeared to accumulate more free proline and fewer reactive oxygen species (ROS), and elevate the activities of antioxidant enzymes. In contrast, RNA interference (RNAi) of OsDRZ1 led to lower activities of antioxidative response and more sensitivity to drought. RNA sequencing analysis revealed that the genes down-regulated by OsDRZ1 were mostly down-regulated by drought, implying the critical role of OsDRZ1 in modulating drought-responsive gene expression. A cupin gene OsGLP1 (germin-like protein1) was identified as one of the potential target genes of OsDRZ1, as suggested by real-time PCR and transient expression analysis in rice protoplasts. Moreover, overexpression of OsDRZ1 did not lead to growth inhibition but the promotion of rice growth, implying the potential application prospective of OsDRZ1 in engineering drought-tolerant crops. [ABSTRACT FROM AUTHOR]