Studies On The Physiological Characteristics And Gene Fine Mapping For Yellow-green Leaf Mutant Ygl In Rice

The chloroplast of plant cells is known as "manufacturing plant nutrients" and "energy conversion site". The chloroplasts play a very important role in plant photosynthesis. The chlorophyll deficient mutant is a common mutant feature in rice. Gene mutations about Chlorophyll directly or indirectly lead to the change when the chlorophyll synthesize or degradate in a step, causing the leaves color change. The chlorophyll mutant is also known as leaf color mutant. The leaf color mutant is not only the study of plant photosynthesis, chlorophyll synthesis, chloroplast genetic differentiation and development of materials, but also it is applied to heterosis utilization as a marker trait. Therefore, they have important theoretical significance and application value to explore and firm rice leaf color mutant gene, and carry out the mapping, cloning and functional analysis of chlorophyll-related genes.Yellow-green leaf mutant (Ygl) was isolated by EMS mutagenesis for a japonica rice(Oryza sativa L.) variety Xiushui09. Researching physiological traits of the mutant and mutant gene fine mapping, results are as follows:1. Physiological charateristies of mutant Ygl:Yellow-green leaf mutant exhibited yellow green leaf leaves from seedling to heading stage, whole growth about140days. The plant height did not differ from Xiushui09. The number of tillers reduced. The seed setting rate decreased. The mutant showed a high degree of infertility. Sword leaves changed short and width did not significantly changed compared with wild-type. The experiment shows that the mutation is not sensitive response to light and temperature.2. Surveying photosynthetic parameters of mutants:Surveying chlorophyll content of mutant Ygl and Xiushui09found that, the chlorophyll content of the mutant was significantly lower than the wild-type, and the rate of decline of chlorophyll b is more than chlorophyll a. through the result, infered that chlorophyll b may play a more important role in the mutant. In the pulling out head period, and under the condation of1500μmol protons/m-2/s-1(saturated light) to suevey the net photosynthetic rate ofleaves central at booting, using the portable photosynthesis instrument li-6400(LI-COR.USA). The result indicated that the net photosynthetic rate is not obvious difference between the mutant and Xiushui09.3. Observing mutant chloroplast ultrastructure:According the chloroplast ultrastructure indicated that the chloroplast shapes do not have the difference between mutant and the Xiushui09, but the chloroplast structure have the very sweeping change, in the Xiushui09chloroplasts, the basal granule structure is normal, and the kind of pouch body laminar is clear, the mutant basal granule structure becomes fuzzy, and pouch body laminar changes few.4. Analying mutant Ygl:Mutant Ygl was crossed with Xiushui09, and the F1population of two crossed showed wild-tpye phenotype.It indicated that traits of muant were control by the recessive gene. The F2phenotype is separated, and has the wild phenotype and the mutant phenotype. After the statistics, the wild phenotype and the mutant phenotype fited a ration of3:1. The result indicated that the mutant Ygl was controled by a single recessive nuclear gene.5. Mapping of mutant gene ygl(1) and sequencing of the candidate gene:To map the mutant gene, a F2population was constructed by crossing mutant with indica rice variety Zhenshan97. The ygl(1) was linked to SSR marker RM2459on the chromosome11. Therefore,14InDel markers were developed around the marker, ygl (1) gene was mapped to an82kb region. It was predicted and analyzed by Rice Genome Annotation (http://rice.plantbiology.msu.Edu/overview.shtml) to search candidate gene. Sequencing of the candidate gene from the Ygl mutant and the wild type variety showed that a single base substituted in the mutant.