Genetic Analysis And Fine Mapping Of Dlt2(t) Mutant In Rice (Oryza Sativa L.)

Rice (Oryza sativa L.)is not only one of the most important food crops in China, but also a model plant for studying the developmental biology of monocots. Rice plant height is a key and crucial agronomic trait, which is directly bound up with rice grain production, photosynthetic efficiency and lodging resistance. Therefore revealing the mechanism of plant elongation and controlling plant height for rice breeding application is most instructive.dwarf mutants are crucial for elucidating regulating mechaisms for plant plant growth and development. Altough many rice dwarf related mutant has been identified and further mapped and even cloned.but the essences of dwarfism and regulatory network of genes concerning plant height is still elusive.Hence, the study of novel rice dwarf mutants can facilitate us to shed a brilliant light on the regulatory mechanism of rice plant elongation and cotrolling plant height, as well as providing more available germplasm resource in breeding.In this research, we found a novel dwarf and low tillering mutant, designated tentatively as dlt2(t), derived from the T2 segregation population of transgenic japonica variety Nipponbare,. The dlt2(t) mutant shows two main kinds of phenotype,dwarf and low-tilellering,while pleiotropic phenotype such as dark green, short, sword-like, slightly rolled inward leaves, small and thin panicle ,no fertility are also observed.The main results of this research are summarized as follows:1. Genetic analysis of dlt2(t) mutant. During the heading stage, we crossed the dlt2(t) heterozygous with each of ZF802,NJ06,two indica varieties.both of F1 generation exhibits wild-type phenotype,and the phenotypic ratio of wild type and mutant among F2 popluation by chi-square test ,complied with Mendel segregation ration of 3:1 ,suggesting the dlt2(t) mutant is caused by a single recessice gene. 2. Sensitivtiy analysis of dlt2(t) mutant treated by GA3 and BR. dlt2(t) mutant screented from the F2 progeny in the seeding stage, applied with appropriate exogenous GA3 and BR,respectively,showed that the dlt2(t) mutant is sensitive to both GA3 and BR ,but rice leaf lamina joints assay shows dlt2(t) is less sensitive to BR than wild type plants.3. Fine mapping of DLT2(t) gene. To elucidate the molecular function of DLT2(t), the DLT2(t) gene was fine mapped via map-based cloning approach. The DLT2(t) locus was located on short arm of chromosome 3 by rough mapping. Using total 1056 mutants out of F2 progenies derived from crosses between dlt2(t) heterozygous and each of ZF802,NJ06 .We further delimited the DLT2(t) gene to a ~73.3 kb interval by using SSR, STS and CAPs marker.In this region, Ten open reading frames (ORFs) were predicted,which provided an important basis to finally clone it.