| Spikelet is the ultimate expression site of rice production and also the main storage place for photosynthetic products. The mapping and cloning of genes related to spikelet development is not only conducive to understanding the molecular mechanisms, but also has an important theoretical value for rice molecular design breeding. In this study, a no spikelet mutant nspl was generated and identified from a japonica cultivar ST1209 by ethyl methanesulfonate (EMS) treatment. Genetic analysis revealed that the nspl mutant phenotype was controlled by a recessive nuclear gene. NSP1 was finally fine mapped to an interval of 41.6 kb between zd38 and zd30 by SSR and STS markers in F2 population. Based on rice bioinformatics database,7 predicted ORFs were found in this region. Among them, LOC_Os04g56780 is a WUSCHEL homologous gene involved in shoot apical meristem development, which may be the candidate gene of NSPl. Another no spikelet mutant nsp2 was isolated from an EMS-mutated indica cultivar yundao32. This mutant not only exhibited no spikelet, but also showed a narrow leaf and dwarf phenotype. Genetic analysis revealed that nsp2 was also controlled by a recessive nuclear gene. NSP2 was finally fine mapped to an interval of 442 kb between NL30 and NL38 by map-based cloning method. qRT-PCR analysis indicated that the expression levels of anuxin biosynthesis, signal transduction and transport related genes were down-regulated in nsp2 mutant, suggesting NSP2 is a new narrow leaf gene involving in the auxin metabolism and regulating the development of leaf and spikelet. All these findings provide a foundation for further cloning of NSPl and NSP2, and better understanding the molecular regulation network of panicle development in rice. |
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