Genetic Analysis And Gene Mapping Of A Rice (Oryza Sativa L.) Dwarf Mutant Gene D68

Rice (Oryza sativa L.) is not only one of the most important food crops in China, but also a model plant for studing the developmental biology of monocots. The pathway of gibberellins metablism and signaling transduction has been intensely studied through screening, gene cloning and functional analysis of rice mutants deficited in gibberellin biosynthesis and signaling transduction and important progresses have been made re-cently. However, it is unclear that how gibberellins interacted with other genes in regu-lating the development of rice height. Cloning of more related genes and identification of numerous gibberellins metabolism or signaling transduction deficient mutants is needed in elucidating such a complex pathway.We found a dwarf mutant, named dwarf68 (d68), from Japonica variety Nipponbare treated with EMS. Genetic analysis indicated that the segregation ratio of wild-type to dwarf plants is in accordance with 3:1 in the F2 populations and that d68 is controlled by one recessive gene. Allelic test showed d68 was nonallelic with known dwarf mutants d1, d11, d2 and d63, dwarf1-like which have been cloned by our lab. Therefore, the mutant may be a novel dwarf mutant. Application of GA₃ leds to stem elongation of dwarf mutant d68 which is resemble with that of wildtype, whereas exogenous BRS has little or no effect on the mutant. These results indicate that the mutant is sensitive to GA. To elucidate the molecular function of D68, we used 1,377 dwarf mutants selected in one F2 population derived from the cross between d68 and indica variety Nanjing-6 as mapping population, and the D68 gene was finally finely mapped between the STS Markers LT1 and LT6 on chromosome 1 through map-based cloing strategy. The inter-val length is 61 kb, ORF analysis of this region reveal that there are eight open reading frame (ORF) in this region.