| Rice is one of the most important food crops in the world.Flowering is a key and complex biological process in rice.A rice spikelet closure obstacle mutant named rsc is obtained by fast neutron mutagenesis through the wild type——Kitaake,its target gene——OsAOS1,a key gene in jasmonic acid synthesis pathway and located on chromosome 3 of rice was also identified.In rsc,there is a single base mutation in OsAOS1 gene,and the mutant phenotype can be complemented by genetic complement,which proves that this gene mutation lead to the phenotype of rsc.Therefore,this study researches on rsc phenotype identification,observation of lodicule structure,the detection of endogenous jasmonic acid and related analogues,the treatment of exogenous jasmonic acid,subcellular localization and function of target gene.The main results are shown as follows:(1)The phenotype of rsc is that its lemma is not close at period of flowering end,and grain becomes wider and the seed setting rate is decreased.(2)The lodicule of rsc has expanded before flowering,so lodicule does not expand and contract obviously during flowering.The reason for rsc not closing lemma is that the lodicule keeps expanding at the period of flowering closing.(3)Plant hormone determination of jasmonic acid(JA)shows that the JA content in rsc is 58.9 ng/g at the period that is maximum opening angle during flowering,about 20 lower times than that of Kitaake,1298.8 ng/g.Exogenous plant hormone jasmonic acid treatment shows that it can complement phenotype of rsc.These results both prove that rsc is a jasmonic acid synthesis deficient mutant.(4)The expression product of OsAOS1 gene is located in chloroplast.(5)The expression level of OsAOS1 gene in rsc remains low at period that is going to flowering.Under exogenous jasmonic acid treatment,the expression of this gene increases at the period that is maximum opening angle during flowering.It is also found that the expression of OsMADS2,a gene controlling the size of lodicule,is significantly decreased in rsc,suggesting that OsMADS2 may be located in the downstream of jasmonic acid signal pathway.The purpose of this study is to provide a scientific theoretical basis for further improving the opening and closing mechanism of rice spikelet. |
