Soil salinity seriously impedes rice growth and development and greatly reduces its production and quality. Rice responses to salt stress are precisely controlled by intricate transcriptional regulatory networks mediated by various transcription factors. Here, we identified rice WRKY DNA-binding protein 24 (OsWRKY24) and OsWRKY70 as positive regulators of rice seedling salt tolerance. Loss of both OsWRKY24 and OsWRKY70 functions resulted in reduced rice seedling salt tolerance, whereas overexpression of OsWRKY24 or OsWRKY70 improved rice seedling salt tolerance. Consistently, expression of several stress-related genes was reduced in oswrky24/70 double mutants but enhanced in transgenic plants overexpressing OsWRKY24 or OsWRKY70. Further analysis revealed that OsWRKY24 can directly bind the promoter of OsUGT85E1 to activate its expression and OsWRKY70 also participates in the transcriptional regulation of OsUGT85E1. Similarly, loss of OsUGT85E1 function rendered the rice seedling more sensitive to salt stress, whereas overexpression of OsUGT85E1 improved rice seedling salt tolerance. Interestingly, OsWRKY24 physically interacts with OsWRKY70 to form a functional complex and synergistically activate OsUGT85E1 expression. Genetically, OsWRKY24/70 positively regulates rice seedling salt tolerance in a partially OsUGT85E1-dependent manner. Taken together, our study provides insights into the OsWRKY24/70-OsUGT85E1 module in rice seedling salt tolerance and contributes to the construction of the salt stress-associated transcriptional regulatory networks in rice.
The yield plateau in intrasubspecific hybrids necessitates the exploitation of heterosis in intersubspecific hybrids, combined with the introgression of novel genes from wild species through interspecific hybridization. However, the utilization of this advantage is constrained by postzygotic barriers, most notably hybrid sterility. These barriers arise from allelic incompatibilities at a limited number of rapidly evolving loci rather than from genome-wide divergence, as described by classical and modern extensions of the Dobzhansky-Muller model. Overcoming the effects of hybrid sterility loci while retaining favorable heterotic effects will facilitate the development of superior parental lines, thereby increasing the efficiency of hybrid rice breeding. Accordingly, this review integrates indica-japonica adaptive differentiation, the mechanisms underlying hybrid sterility, and heterosis-associated QTLs (quantitative trait loci) and their underlying regulatory loci to elucidate the genetic factors governing reproductive compatibility and hybrid performance in rice breeding. On this basis, fertility in intersubspecific hybrids can be restored through various strategies including the development of indica-compatible japonica lines, wide-compatible indica lines carrying neutral alleles, and advanced molecular approaches such as genome editing, thereby enabling the development of fertile, high-yielding rice hybrids. These strategies provide a practical framework to unlock the full potential of intersubspecific heterosis while also facilitating the introgression of novel genes from wild species through interspecific hybridization, thereby contributing to sustainable rice productivity under future food security and climatic challenges.
Grain size is a pivotal agronomic trait that determines rice yield and grain quality. It is genetically regulated by multiple genes and interconnected signaling pathways. Numerous grain size-related genes have been identified in rice, but relevant findings regarding regulatory pathways, natural gene variations, signaling crosstalk and breeding applications remain poorly systematically integrated. This review summarizes recent advances in regulatory mechanisms of rice grain size genes, integrates regulatory pathways and signaling crosstalks. We further discussed the multi-gene interaction, trade-offs between these genes and practical breeding application, as well as current major challenges in this field and propose future research directions. The overall aim is to offer a reliable theoretical reference and actionable guidance for the targeted optimization of grain size traits and the development of novel high-yielding, high-quality rice cultivars.
The Mediator complex serves as a critical bridge linking transcription factors (TFs) to RNA polymerase II during mRNA synthesis. Among its subunits, MED25 plays a pivotal role in jasmonate (JA) signaling by directly interacting with the master TF of the JA pathway. However, the biological functions of MED25 in monocotyledonous plants, particularly its contribution to JA-mediated responses in rice, remain largely unexplored. Here, we mutated OsMED25 in rice using CRISPR/Cas9-based genome editing and evaluated JA-mediated developmental and defense phenotypes in these osmed25 mutants, JA-deficient allene oxide cyclase (osaoc) mutants, and wild-type plants. We found that osmed25 mutants exhibited defective anther dehiscence and open husks but normal spikelet morphology, whereas osaoc displayed severe spikelet developmental defects, including non-dehiscent anthers. Notably, OsMED25 is essential for rice resistance against the brown planthopper (BPH). While osaoc mutants completely lost JA responsiveness, osmed25 mutants displayed only partial impairment of BPH-induced JA-responsive gene expression, accompanied by a selective reduction in the accumulation of defensive specialized metabolites (e.g., phenolamides and volatile terpenes). Furthermore, OsMED25 participates in a feedback loop modulating JA biosynthesis during BPH infestation. Collectively, our study uncovers the role of OsMED25 in regulating a subset of JA-dependent spikelet development and herbivore resistance in rice.
The central endosperm of a chalky rice mutant JM03, which was isolated from a 60Co-irradiated mutant population of the indica rice variety 93-11, contains numerous small, irregularly shaped starch granules with looser packing than those of the wild type (WT). JM03 starch showed lower gelatinization onset and peak temperatures, reduced pasting viscosities, and consistently decreased dynamic rheological parameters compared with WT. Through bulked segregant analysis sequencing (BSA-seq), complementation tests, and immunoblot analysis, we identified PPDKB (Os05g0405000) as the causal gene underlying the JM03 phenotype. Multi-omics analysis of developing endosperm at 15 d after flowering revealed that PPDKB deficiency profoundly redirected central carbon and amino acid metabolism. On the one hand, impaired phosphoenolpyruvate regeneration disrupted the gluconeogenic conversion of hexoses into starch biosynthesis precursors, consequently suppressing starch accumulation through downregulation of all starch synthesis-related genes and enzymes. The impaired starch synthesis diminished sucrose unloading capacity due to reduced expression of sucrose synthase, triggering accumulation of sucrose and other soluble sugars. On the other hand, excess pyruvate diverted metabolic flux towards acetyl-CoA production, stimulating tricarboxylic acid (TCA) cycle activity and enhancing lipid biosynthesis. Meanwhile, amino acid synthesis was enhanced due to increased levels of multiple precursors and genes/enzymes involved in this process. The reduction in starch accumulation, combined with the downregulation of key grain weight regulators, such as mitogen-activated protein kinase 6 and BAHD acyltransferase-like protein, collectively led to a significant reduction in grain weight in JM03. Taken together, our study reveals a functional cross-talk between starch, soluble sugars, protein, and lipids in rice endosperm during seed development in JM03, which provides important germplasm resources and a theoretical basis for genetic improvement of rice yield and quality.
Fulvic acid (FA) has been widely used as a plant growth regulator to alleviate salt stress. However, the mechanism by which it enhances salt tolerance in rice remains unclear. This study systematically investigated the chemical structure of FA and its role in enhancing rice salt tolerance through the regulation of plasma membrane (PM) H+-ATPase. The results demonstrated that the increased molecular weight (MW) of FA companied by progressive aromaticity enhancement and functional group depletion. Principal component analysis revealed that low-MW FA fractions (< 3 kDa), enriched in carboxylic-C, phenolic-C, and lignin-like substances, exhibited a strong positive correlation with root growth, membrane potential (MP) hyperpolarization, and Na+ efflux under 100 mmol/L NaCl stress. Mechanistically, FA directly activated PM H+-ATPase (activity increased by 30.3%‒86.2%), generating a proton gradient that energized SOS1 to mediate Na+ efflux, leading to salt tolerance in rice. Genetic validation using osa1 knockout mutants confirmed the indispensable role of PM H+-ATPase in FA-induced responses, as both MP and Na+ efflux remained unaltered upon FA1‒FA5 treatment. This research found that FA fractions with high functional group density and low aromaticity can serve as optimal plant biostimulants for salt stress mitigation, providing a new strategy for sustainable lignite valorization in precision agriculture.
Chelerythrine is one of the most abundant alkaloids in the traditional Chinese medicinal herb Chelidonium majus L. We aimed to develop a wettable powder formulation containing chelerythrine,and to clarify the mechanism by which chelerythrine induces apoptosis and autophagy in Spodoptera frugiperda clone 9 (Sf9) cells,thereby promoting the application and development of chelerythrine in plant protection.
The central endosperm of a chalky rice mutant JM03, which was isolated from a 60Co-irradiated mutant population of the indica rice variety 93-11, contains numerous small, irregularly shaped starch granules with looser packing than wild-type (WT). JM03 starch showed lower gelatinization onset and peak temperatures, reduced pasting viscosities, and consistently decreased dynamic rheological parameters compared to WT. Through BSA-seq, complementation tests and immunoblot analysis, we identified the pyruvate orthophosphate dikinase (PPDKB, Os05g0405000) as the causal gene for JM03. Multi-omics analysis of developing endosperm at 15 days after flowering revealed that PPDKB deficiency profoundly redirected central carbon and amino acid metabolism. On the one hand, impaired phosphoenolpyruvate regeneration disrupted the gluconeogenic conversion of hexoses into starch biosynthesis precursors, consequently suppressing starch accumulation through downregulation of all starch synthesis related genes and enzymes. The impaired starch synthesis diminished sucrose unloading capacity due to reduced expression of sucrose synthase, triggering accumulations of sucrose and other soluble sugars. On the other hand, excess pyruvate diverted metabolic flux towards acetyl-CoA production, stimulating TCA cycle activity and enhancing lipid biosynthesis. Meanwhile, amino acid synthesis was enhanced due to increased levels of multiple precursors and genes/enzymes involved in amino acid synthesis. The reduction in starch accumulation, combined with the downregulation of key grain weight regulators such as mitogen-activated protein kinase 6 and BAHD acyltransferase-like protein collectively led to a significant reduction in grain weight in JM03. Taken together, our study unraveled a functional cross talk between starch, soluble sugars, protein and lipids in rice endosperm during seed development in JM03, which provided important germplasm resources and theoretical basis for genetic improvement of rice yield and quality.
In genomic breeding, approaches centered on genome-wide association study (GWAS) have elucidated many loci underlying target traits. However, the conventional approaches focusing on the effects of independent genetic factors do not properly reflect phenotypic variation arising from interactions between genetic background and environmental conditions. In this study, regarding yield-related traits in rice, we focused on two strong GWAS peaks for grain number (GN), corresponding to the known genes NARROW LEAF1 (NAL1) and Oryza sativa SPINDLY (OsSPY). NAL1 negatively regulated GN in a nitrogen-dependent manner, whereas OsSPY positively regulated GN irrespective of nitrogen conditions. Examination of haplotype combinations across nitrogen conditions using imbalance-aware statistical estimation allowed modeling of the interaction effects of NAL1 and OsSPY on GN. Specifically, under low nitrogen conditions, the effect of NAL1 was markedly enhanced, being approximately two-fold greater in the background of the low-activity OsSPY haplotype than in that of the high-activity haplotype. These findings provide a framework integrating haplotype combinations with environmental context to better explain phenotypic variation, thereby highlighting genotype-by-genotype-by-environment (G × G × E) interactions underlying rice performance under variable environmental conditions. This perspective complements and extends conventional genetic approaches, enabling a deeper understanding of complex trait architecture in natura.
