水稻颖壳不闭合基因SG5的鉴定与克隆OA

[Objective]Rice glume development directly affects both grain yield and quality.Identifying genes that control glume development and characterizing their functions can provide valuable genetic resources for breeding.[Method]The split glume 5(sg5)mutant was isolated from a mutant library generated by ethyl methanesulfonate(EMS)mutagenesis of the rice variety Xudao 3(XU3).Phenotypic investigation and analysis were performed on both the wild type and the sg5 mutant.SG5 was identified using a combination of map-based cloning and bulked segregant analysis sequencing(BSA-seq).The temporal and spatial expression patterns of SG5 were examined by qRT PCR and GUS staining.Subcellular localization of SG5 was observed in rice protoplasts.An evolutionary tree was constructed to analyze the natural selection of SG5.[Result]The mutant exhibited normal glume development before flowering,but the glumes remained split until maturity.Compared with the wild type,the mutant showed earlier heading,longer panicles,reduced grain length and width,and a significantly lower seed-setting rate,while plant height and effective panicle number remained unchanged.Microscopic observation indicated that the split glume phenotype was caused by persistent swelling of the lodicules.SG5 was mapped to a 3.72 Mb physical interval between InDel5-11 and InDel5-13 on chromosome 5.In the sg5 mutant,a G-to-A mutation at the junction of intron 3 and exon 4 of LOC_Os05g50890 led to alternative splicing and premature protein termination.Knockout experiments confirmed that SG5 is the target gene.SG5 is constitutively expressed,with higher transcript levels in roots,stems,and leaves.The SG5 protein localizes to both the cytoplasm and nucleus.Evolutionary analysis revealed that SG5 has undergone differentiation between indica and japonica subspecies during evolution.[Conclusion]This study identifies a novel allele of OsJar1 and reveals that SG5 has diverged between indica and japonica under natural selection.These findings provide new clues for further dissection of the molecular regulatory network controlling glume development and offer valuable genetic resources for precision breeding in rice.