As a sessile organism, rice often faces various kinds of abiotic stresses, such as drought stress. Drought stress seriously harms plant growth and damages crop yield every year. Therefore, it is urgent to elucidate the mechanisms of drought resistance in rice. In this study, we identified a glycine-rich RNA-binding protein, OsGRP3, in rice. Evolutionary analysis showed that it was closely related to OsGR-RBP4, which was involved in various abiotic stresses. The expression of OsGRP3 was shown to be induced by several abiotic stress treatments and phytohormone treatments. Then, the drought tolerance tests of transgenic plants confirmed that OsGRP3 enhanced drought resistance in rice. Meanwhile, the yeast two-hybrid assay, bimolecular luminescence complementation assay and bimolecular fluorescence complementation assay demonstrated that OsGRP3 bound with itself may affect the RNA chaperone function. Subsequently, the RNA-seq analysis, physiological experiments and histochemical staining showed that OsGRP3 influenced the phenylpropanoid biosynthesis pathway and further modulated lignin accumulation. Herein, our findings suggested that OsGRP3 enhanced drought resistance in rice by altering the phenylpropanoid biosynthesis pathway and further increasing lignin accumulation.

The cytoplasmic male sterility (CMS) and nuclear-controlled fertility restoration system is a favorable tool for the utilization of heterosis in plant hybrid breeding. Many restorer-of-fertility (Rf) genes have been characterized in various species over the decades, but more detailed work is needed to investigate the fertility restoration mechanism. Here, we identified an alpha subunit of mitochondrial processing peptidase (MPPA) that is involved in the fertility restoration process in Honglian-CMS rice. MPPA is a mitochondrial localized protein and interacted with the RF6 protein encoded by the Rf6. MPPA indirectly interacted with hexokinase 6, namely another partner of RF6, to form a protein complex with the same molecular weight as the mitochondrial F₁F₀-ATP synthase in processing the CMS transcript. Loss-of-function of MPPA resulted in a defect in pollen fertility, the mppa^+/− heterozygotes showed semi-sterility phenotype and the accumulation of CMS-associated protein ORFH79, showing restrained processing of the CMS-associated atp6-OrfH79 in the mutant plant. Taken together, these results threw new light on the process of fertility restoration by investigating the RF6 fertility restoration complex. They also reveal the connections between signal peptide cleavage and the fertility restoration process in Honglian-CMS rice.

As a special class of rice germplasm, wide-compatibility varieties (WCVs) guarantee the fertility of hybrids when there is cross-fertilization between two subspecies. In this study, Chenghui9348 was identified as a new member of the WCV family that improves pollen fertility in an inter-subspecific hybrid. Cytological analysis showed that the abnormal mitosis of microspores resulted in the sterility of pollens at the early bicellular stage in the inter-subspecific hybrid. Furthermore, the new F12 locus, corresponding to improvements in fertility of the indica-japonica hybrid, was found to co-segregate with the RM1047 marker and associated with a region of approximately 630 kb flanked by the D1101 and D1164 markers on chromosome 12. In this region, two putative genes were predicted as the candidates for wide-compatibility genes (WCGs). Sequence analysis revealed that, compared with indica/japonica alleles, deletion/insertion occurred within exons of both putative genes. Together, the present study identified another new WC locus, F12, and offers more opportunities for further exploitation of inter-subspecific hybrids in rice.