Mapping Of A Short Root Gene Osksr2in Rice (Oryza Sativa L.)

Root is an important organ of a plant，which is formed by a long-term adoption of a certainland condition. It has many functions, such as anchoring the plant, absorbing moisture and nutrientfrom the soil and then conducting them, synthetizing and storing nutrition. Because of thelimitation and the locality of the supply of nutrient and moisture of the soil, the roots’ spatialdistribution, also called root architecture, determine the ability of the plants in absorbing andutilizing nutrient and moisture in the soil. Root length as the most important factor of a plant, islargely related to the characters of the plant and mostly affect the production and stress resistancecapacity of a plant. Variation is the basis of functional analysis, so the most powerful material tostdudy the mechanism of root elongation is the short or long mutant。The genetic analysis of themutants has been proved to be a effective way to reveal the mechanism of root elongation.In this study, a rice mutant with significantly short roots was isolated from an EMS(ethylmethane sulfonate)-generated mutant library of Kasalath and named as Osksr2(Oryza sativakasalath short root2). Osksr2showed a dwarf phenotype and the elongation of primary roots.Analysis of pollen staining and morphology at mature stage showed that Osksr2mutation greatlyaffects plant reproduction, reduces pollen activity and seed fertility.Osksr2is also a temperature sensitive mutant, the Osksr2displays a distinct defect in rootelongation under32℃, while it is somewhat rescured under24℃. Physiological test showed theshortroot in the mutant is insensitive to application of phytohormones GA. Genetic analysisindicated that the mutant phenotype was controlled by a single recessive nuclear gene, and namedas OsKSR2. To map OsKSR2, we generated an F2population by crossing Osksr2withNipponbare wild type. By using the published SSR markers and newly designed STS markers,OsKSR2was mapped to a101kb region between the markers S27887and S27988on chr.8.Within this region there were seventeen predicted genes, and none of them had been reported to beinvolved in root development. The study will be helpful for the cloning of OsKSR2andcharacterization of the molecular mechanism of root elongation in rice.