The Genetic Ananlysis And Gene Maping For The Unclosed-glume (ucgl) And Long Root (lr1) Mutants

Rice is one of the most important food crops in China and it is the model plant on molecular biology research of monocotyledon development, the number and size of the flower organs is one of the determinants of rice yield formation. Finding more flower organ mutants has an important theoretical significance, and identification and cloning of the gene(s) for rice floral organ mutants is of practical value to the study of the monocotyledon flower development mechanism as well as the root system of rice which the main part that absorbs water and nutrients play an important role in its vegetative and reproductive growth. In this study an unclosed-glume mutant (ucgl) and a long root mutant (lorl) were isolated from rice cultivar Nipponbare by mutagenesis with ethyl methanesulfonate. Identification and gene maping of the UCGL gene and LR1 gene have certain reference value to better understand the genetic and molecular mechanism of the flower organs and root from the molecular level. The main results were as follows: For the ucgl mutant:1. After flowering the lemma and pelea of the ucgl could not closed. At maturity the shape of the rice became sharp, the seed setting rate was significantly lower and the number of main cob vascular bundles and secondary branch vascular bundles reduced and there was no difference in the first branch vascular bundle. The dissected survey showed that the lodicules of mutant exhibit no difference compared with its wild type, but they could maintain plumpness status for a much longer time and it may be one of the most important external reason for the non-closure of the glumes.2. The results of genetic analysis indicated that in the F2 population crossed by ucgl mutation and cultivar Nipponbare, a total of 182 wild type plants and 48 unclosed-glume plants were obtained. The segregation rates of the wild type and ucgl mutation fited a ratio of 3:1 (X2=2.89<X20.05=3.84), which means the ucgl mutation was controlled by a single recessive nuclear gene.3. The gene was primary mapped on the long arm of the chromosome 8 between SSR markers RM23242 and RM23265, and the UCGL gene was finally located in 118Kb region between R8UM89 and RM23258 markers. Acording to the ratebase it was foud that there were 13 ORFs. Through DNA and cDNA sequenceing a base substitution (C-T) was foud on the Os08g0459600, which encodes a 12-oxo-phytodienoic acid reductase 7 which is a key enzyme in the biosynthesis of jasmonic acid (JA) and the content of endogenous JA of rice panicles was lower than that in wild type at different flowering time. The Os08g0459600 gene was comfirmed to the best candidate gene of UCGL.For the lrl mutant:1. Maximum root length, lateral root number and root cap ratio of the mutant were determined with the results showing that the maximum root, the root-shoot ratio and number of lateral root of lrl mutant were significantly greater than that in the wild type, and the lateral root number had no significant diffrence between lrl mutant and wild type. Ananysis of panical traits found that the 1000-grains, ear length, first branches, secondary branches and the vascular bundles of the main cob in lrl mutant were greater than those in the wild type.2. Genetic analysis indicated that in the F2 population crossed by lrl mutation and cultivar Nipponbare, a total of 136 wild type plants and 64 long root plants were obtained. The segregation rate of the wild type and lrl mutation fited a ratio of 3:1 (X2 = 2.405<X20.05= 3.84), demonstrating that the mutant phenotype of the long root was controlled by a single recessive gene.3. Finally, the LR1 gene was found to be located between the SSR markers RM304 and RM7300 on chromosome 10, and the genetic distance is 2.0 cM and 3.5 cM respectively.