Physiological Study, Genetic Analysis And Molecular Tagging Of Related Gene For One Agravitropism Mutant From Rice

Rice (Oryza sativa L) is an important worldwide cereal crop,as well as a model plant for molecular biology research.Although rice agravitropism mutant (lazy- rice) was reported in 1938,little research has been done about it.At present,related gene characterization or clone has not been reported ,and then related molecular mechanism is also unkown.To learn molecular mechanism on gravitropism of rice ,we have obtained a rice agravitropism mutant (lazy-2) from MI population of indica line E428,which was treated by EMS.The characters of this mutant rice include down-growth during seedling and lazy growth habit(prostrate growth) since tiller.and other characters are normal.lt has been shown through preliminary physiologic research that exogenous phytohormones and light have not any effect on the agravitropism character of this mutant lazy-2,which has no response to gravity, the result of genetic analysis for lazy-2 mutant indicates that this mutation is controlled by a single recessive gene .And related gene has been mapped between two SSR marker on 11 chr The main results are summarized as follows:1. The phenotype of WT and lazy-2 mutant has no change in MS with different concentrations of exogenous phytohormones (2,4-D and gfbberellin),compared with normal conditions.But the development of both have been inhibited with higher concentrations.the both phenotypes are not obvious.The results has shown that exogenous phytohormones have no obvious affection on growth habits of la-2 mutant.2. After growth for 7 days in continuous light and continuous darkness, the phenotypes of WT and lazy-2 mutant are like as those in normal conditions. The results has also shown that light has no obvious affection on growth habits of la-2 mutant.3. WT and lazy-2 mutant grow in different gravitational field(located invertly and levelly).The upper and underground organs of WT are all able to sense gravity.Whereas the upper organs(stem) of lazy-2 mutant has't any response on gravity under all conditions and grow downward.But the roots has ability to sense gravity and has positive gravitropism.4. The result of genetic analysis for lazy-2 mutant indicates that this mutation is controlled by a single recessive gene.But it crossed with indica lines II-32B.D62B and E428 respectively, the phenotype of Ti was recessive, similar with WT.While lazy-2 was crossed with othe lines such as R527 and R363, the phenotype of Fi was codominant.The Fa population from lazy-2 mutant crossed with D62B was used to screen molecular markers linked with the related gene la-2.5. Furthermore.the gene was mapped between two SSR markers,LU2 and LU18 on chromosome 11,with genetic distances of 1.0 cM and 1.7cM .respectively. Electronic hybridization makes it realistic that the area covering the gene has been integrated with physical map of chromosome 11 provided by IRGP.and possible physical distance is 140-200 kb between makers LU2 and LlMS.Then the results will be the basis of the aim to obtain the gravitropic gene and study the molecular mechanism on rice gravitropism.