Fine Mapping A Of DLT Mutant In Rice(Oryza Sativa L.)

Rice(Oryza sativa L.)is one of the most important food crops in the world. Two-thirds of the world population feed on rice. However, with the rapid population groweth and the arable land decreasing, how to increase the rice yield further has become the primary concern of breeders. Plant height is one of the most important agronomic traits of rice, which directly affects yield potential and lodging resistance. Therefore, insight into the genetic and regulatory mechanism in the rice plays a supporting role in rice plant architecture.In recent years, more and more genes related to rice dwarfing have been found. Over70genes about dwarf and semi-dwarf have been cloned. However, only a very small number of these dwarfing genes have been actually used in breeding. Therefore, we need a further understanding of the physiological and biochemical mechanisms of rice plant height as well as digging more new genes related to rice plant height to expand dwarf source for breeding.A rice dwarf mutant with fewer tillering, tentatively named dwarf and low tillering (dlt), was identified from the mutant library of the State Key Laboratory of Rice Biology. This mutant has phenotypes of severe dwarf, with plant height about10-15cm; less tillering, generally1-3tillers; developmental delay; deepened leaf color; short upright inward rolled and sword-shaped blades; small and sparse spikelets. In this research, the gene DLT was fine mapped through map-based cloning and the candidate genes are analysised based on it. Furthermore, related studies on physiology have been performed.The results are as follows:1. The determination of chlorophyll between wild-type and mutant reveal that mutant leaves has a less chlorophyll content, especially in parts of the content of chlorophyll a;2. Wild-type and mutant plants were treated with exogenous hormones GA3and BR. The results show that the mutant plants are more sensitive to GA3and BR, compared with the wild type;3. Slicing observation indicated that there were fewer and more disorderly main vein catheters in mutant leaves. Furthermore, the main stem in mutant plant has a decreased number of vascular cells. Narrower leaf sheath were also found in the mutant;4. Transmission electron microscope observation showed smaller and a decreased number of starch grains in mutant chloroplst; Scanning electron microscope observation showed irregularly oriented epidermal cells and a decreased number of silica protrusions on the surface, which were less obvious;5. The gene DLT was finally mapped to a73.3kb region, which contains10open resding frames. Sequencing analysis of the10candidate genes reveals that there is no difference between the mutant and wild type. Therefore, we guess that the dwarf phynotype showed by mutant may be controlled by the epigenetics;6. The results of RT-PCR show that the mutant has a significantly reduced expression of the DLT gene in the roots, clum, leaf sheath and SAM, compared with the wild type; Determination of DLT methylation levels in the wild type and mutant gene showed that the methylation degree in wild type is higher than that in the mutant.