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Outline
Grain size is a critical determinant of rice yield. This study aims to explore novel genes regulating grain size and expand the current genetic regulatory network, and provide valuable genetic resources for molecular design breeding of high-yield rice varieties.
The large-grain mutant gsn4, generated by EMS mutagenesis of the japonica rice variety W7, was used as experimental material. A combination of systematic phenotypic identification, cytological observation, gene mapping, functional verification, subcellular localization, and haplotype analysis was performed to clone and functionally characterize the candidate gene.
Phenotypic identification revealed that the gsn4 mutant exhibited pleiotropic effects. Compared with the wild type, its grain length, grain width, and 1000-grain weight were significantly increased, whereas plant height, panicle length, and grain number per panicle were significantly decreased. Cytological analysis indicated that GSN4 regulates rice grain size by modulating both cell proliferation and expansion in glumes. Map-based cloning, together with CRISPR/Cas9 gene-editing validation, confirmed LOC_Os04g46450 as the candidate gene underlying GSN4. This gene encodes a nuclear-localized E3 ubiquitin ligase protein, which acts as a negative regulator of rice grain size and modulates plant growth and development through the brassinosteroid (BR) biosynthesis pathway. Haplotype analysis further identified Hap1 as the elite haplotype conferring the most favorable effects on grain width and 1000-grain weight.
Collectively, this study elucidates the function and regulatory mechanism of GSN4, enriches the genetic regulatory network governing rice grain size, and provides important genetic resources and a theoretical basis for molecular design breeding of high-yield rice varieties.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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