Fine mapping and characterization of a novel dwarf and narrow-leaf mutant dnl1 in rice.

Plant height is one of the most important agronomic traits of rice (Oryza sativa). Dwarf mutants are ideal materials for research on the mechanisms of regulation of rice plant height. We examined a new dwarf and narrow-leaf mutant dnl1. Phenotypic analysis showed that the dnl1 mutant has a thinner culm and more tillers, but the number of grains per panicle, the seed setting rate and the grain weight of dnl1 mutant were found to be significantly lower than in the wild-type. Based on scanning electron microscopic observations, the number of cells in the y-axis in internodes was significantly lower than in the wild-type. In phytohormone induction experiments, dnl1 was gibberellic acid-insensitive. The expression of some genes involved in the gibberellins metabolic pathways was affected in the dnl1 mutant, based on the real-time PCR analysis, suggesting that the dnl1 gene likely plays a role in gibberellin metabolic pathways. Genetic analysis showed that the dwarf and narrow leaf phenotype is controlled by a novel single recessive gene, here referred to as the dwarf and narrow leaf 1 (dnl1), which is located within the region between markers Ind12-11 and RM8214 on the short arm of chromosome 12. By means of fine-mapping strategy, the dnl1 gene was localized within an interval of 285.75 kb physical distance. These results will be useful for dnl1 gene cloning and to improve our understanding of the molecular mechanisms involved in the regulation of growth and development of rice.