Gene Mapping Of A Novel Mutant Abnormal Hull And Lodicule (ahl) In Rice

Recently, Molecular genetic mechanism of floral organ development in plant becomes a hot topic among researchers. The monocot and dicot had their own development processes before 1.2～1.8 billion year, moreover, the character of floral organ of monocot is different from dicot. However, they have similarities and homologist. At the present, the comprehension of floral development based on the results of studying on Arabidopsis thaliana, Antirrhinum majus and Petunie hybrida. In model material rice, with the increasing number of floral development genes been cloned by researchers, these genes laid the foundation in researching of inherit mode of flower in the future.In this study, we have found a flower mutant which abnormal hull and lodicule from EMS-treated Jinhui10 (Oryza sativa L. ssp. indica.). The results as follows:1 Phenotypic Observation and Histological Analysis of ahlIn the early development of spikelet, flower primordium development in ahl and wild type were similar. In flowering stage, we used stereomicroscope to observed spikelet, the first whorls palea and lemma are narrowly and bending, the whole ahl become smaller. The second whorls lodicule in ahl. compared with wild type, showed largen basal and elongated apical lodicules, and had the trend of transforming to glume tissue.2 Agronomic Characters Analysis of ahlArea of lemma in wile-type is 31.08 mm2; which in ahl is 75.1% of the wild type, exhibit significant difference. Area of pelea in wile-type is 15.40 mm2, which in ahl is 87.3% of the wild type, are significantly different. Area of lodicules in wild-type is 0.61 mm2, which in ahl is 214.8% of wild type, exhibit significant difference. The grain length, width and thickness in ahl are 81.1%, 83.3%,94.7% respectively of wild-type. Weight of grain in wild type is 27.4 g, weight of 1000-grain in ahl is 22.8g, are significant difference.3 Genetic AnalysisThe genetic analysis was conducted on the F1 hybrids and F2 populations obtained from XinonglA and ahl cross. The F1 population of this cross showed wild type phenotype. In the F2 populations, the segregation rates of wild type to ahl phenotypic plants fit the ratio of 3:1(χ2= 0.8868<χ2 0.05= 3.84). Therefore, the ahl phenotype is controlled by a single recessive gene.4 Molecular MappingWe used SSR markers to analyze F2 populations of XinonglA×ahl cross, the gene AHL was mapped between SSR marker RM14153 and RM14167 on chromosome 2, with genetic distance of 1.19 cM and 1.34 cM, physical distance of 226 kb in Nipponbare.5 Candidate Gene AnalysisWe have found a LEUNIG homologous gene Os02g56880 in the mapping location, where had 46 genes. The transcription of LEUNIG gene influences AG gene expression, and independently controll cell proliferation of petal, vascular bundle of petal and polarity of floral organ in Arabidopsis. The lodicule of rice corresponding to the petal of Arabidopsis became longer and longer. We preliminarily presumed that this LEUNIG homologous gene Os02g56880 is AHL candidate gene, the identification of its function is in progress.