Fine Mapping Of Two Leaf Color Genes In Rice(Oryza Sativa L.)

Crop biomass and economic yield mainly depend on the photosynthesis of leaves and other photosynthetic organs. 90-95% dry matter accumulation in rice is resulted from photosynthesis of leaves, the main photosynthetic organ. Therefore it is very important in the theoretical research of photosynthesis regulatory mechanism to map and clone new rice photosynthetic-related genes and investigate their function. Through the gene engineering approach, the photosynthesis ability and economic efficiency of rice may be significantly increased .As an obvious trait mutation, leaf color mutation could not only used in the research of photosynthesis, chlorophyll biosynthesis, structure, function, inheritance, differentiation and growth of chloroplast, but also in the identification of seed purity for hybrid rice.A yellow-green leaf mutant ygl2, origined from a Wuyunjing 7, Rice cultivar Wuyunjing 7, Jiangxi 1587 (upland rice) were used in this study. Two reciprocals (Wuyunjing 7Xygl2, Jiangxi1587Xygl2) were made to obtain F₁ and F₂ populations . The observation of leaf color showed that all the F₁ plants were normal green, but the leaf color trait in the all F₂ populations was segregated into yellow green and normal green. The segregation ratio was fitted to 1:3, and it indicated that the mutant ygl2 color was controlled by a single recessive nuclear gene. The plants of F₂ population, generated from the cross ygl2XJiangxi 1587, were used for molecular mapping of this recessive gene. The preliminary results showed that the mutant gene was located on the rice chromosome 6 between two SSR markers, RM6298 and RM7434, with the genetic distances of 0.62cM and 0.74cM respectively. In order to establish the fine location of the ygl2 gene, 56 new SSR and STS markers were developed. With above 56 new SSR and STS markers, the gene ygl2 was mapped between SSR6-22 and STS6-22 markers, with genetic distances of 0.026 cM and 0.078cM respectively. The physical distance of this two markers is 19kb, we found a gene encode heme oxygenase maybe is the ygl2 mutant candidate gene in this region.Presenescing leaf mutant (psl1) is a specific leaf color mutant, induced by Co60 irradiation from a Zhonghua11, Rice cultivar Nanjing6, Nanjing11 were used in this study. Two reciprocals (Nanjing6Xpsl1, Nanjing11Xpsl1) were made to obtain F₁ and F₂ populations . The observation of leaf color showed that all the F₁ plants were normal leaf color, but the leaf color trait in the all F₂ populations was segregated into Presenescing leaf and normal leaf. The segregation ratio was fitted to 1:3, and it indicated that the mutant psl1 was controlled by a single recessive nuclear gene. The plants of F₂ population were used for molecular mapping of this recessive gene. The preliminary results showed that the mutant gene was located on the rice chromosome 2 between two SSR markers, RM5472 and RM425, with the genetic distances of 8.02 cM and 3.78cM respectively. In order to establish the fine location of the psl1 gene, 35 new STS markers were developed. With above 35 new STS markers, the gene psl1 was mapped between STS2-19 and STS2-26 markers, with genetic distances of 0.11 cM and 0.43cM respectively. The physical distance of this two markers is 48kb, and we find marker STS25 was cosegregating with psl1 gene. This result was very useful for cloning of the psl1 gene.