Genetic Analysis And Fine Mapping Of PGL11(Pale Green Leaf 11) In Rice(Ooryza Sativa L.)

At present,with the rapid development of life science,as the most representative pattern plant,rice has gradually become a hot spot to study.Rice leaf color mutant is an important germplasm resource for studying its genetic mechanism and functional genomics.Chloroplast is the main site of photosynthesis and able to convert light energy into chemical energy and provide the energy for life activities.In this study,we identified a pale green leaf mutant named pgl11（pale green leaf 11）which was able to stably inherit from an ethyl methylsulfonate（EMS）-induced mutant library.The changes of rice plant growth caused by PGL11 mutation were analyzed and described from the aspects of morphology,physiology and transcription level,and the gene was located by the method of cloning,these will facilitate the positional cloning and shed light on the research on molecular mechanism of the formation of leaf color mutation and the study of functional genomics of rice.The results of this study are as follows:1.From the seedling stage,every new leaf of pgl11 showed pale green,and as the leaves mature,the leaves’color gradually turned green.The result of transmission electron microscopy（TEM）showed that the number of chloroplasts in the mesophyll cells of the mutants decreased and even have no chloroplast structures,the development of the chloroplasts were abnormal,and there was no normal stacking and formation of starch granules.Compared with WT,the chlorophyll content of pgl11decreased at seedling stage,but there was no significant difference in chlorophyll content at heading stage.2.The photosynthetic rate and stomatal conductance of pgl11 were significantly decreased,while the intercellular CO₂ concentration increased.The result of scanning electron microscopy showed that the stomata of pgl11 developed abnormally,and there was no papilla around the stomata.3.There were no significant differences in tiller number,spike length,number of branches and leaf length between WT and pgl11,but the plant height,flag leaf width,number of secondary branches,number of grains per panicle,grain width,the 1000-grain weight and the setting rate of pgl11 were significantly decreased,while the grain length and grain length-width ratio were significantly higher than WT.4.The expression level of genes associated with chlorophyll synthesis,photosynthesis and chloroplast development was measured and the result shows that pgl11 increased the expression level of chloroplast transcription and translation genes,but reduced the expression level of chlorophyll synthesis and photosynthesis genes.5.The expression of chlorophyll degradation and senescence-related genes in flag leaf and senescence leaf of WT and pgl11 were also measured and the results showed that there was no significant difference in the flag leaf between WT and pgl11,but in the senescence leaf,the expression levels of pgl11 were significantly increased.Dark induction experiment showed that the mutation of PGL11 can promote senescence in rice,further.6.Genetic analysis showed that the mutant phenotype was controlled by a pair of recessive nuclear genes.The gene was narrowed to a 110 kb inteval between the markers C6 and C8 in the chromosome 1,which provided reference for the final cloning of the target gene.