| Rice is not only the most important food crops in the world but also the model plant of monocotyledons.The leaf color mutation of rice is an ideal material for positive research on chlorophyll synthesis and degradation,composition and regulation mechanism of plant photosynthetic system in higher plants,which provides theoretical support for rice breeding with high light efficiency.In the present study,a new green revertible white-stripe mutant,wsl887,was isolated from Qiao-gang Pearl Rice,a local rice germplasm in Guizhou,by 60Co-?radiation.Phenotypic characteristics,photosynthetic pigment content and chloroplast ultrastructure of wsl887 were observed.A genetic mapping population was constructed for gene mapping.q RT-PCR was used to analyze the expression levels of genes related to chlorophyll synthesis,photosynthesis and respiration in the mutant and wild-type at different temperatures.The main results are as follows:1.Under field conditions,the mutant wsl887 showed a white stripe phenotype at seedling stage,but the new leaves gradually returned to a normal leaf phenotype.However,In the mature stage,wsl887 showed no significant difference in the plant morphological characteristics compared with the wild-type,and there were no significant differences in main agronomic traits,such as plant height,effective spike,spike length,seed setting rate and 1000-grain weight.2.The wsl887 is a novel thermo-sensitive leaf color mutant in rice.The phenotype of wsl887 was induced by temperature.The wsl887 at 20?showed a complete albino phenotype,little photosynthetic pigment content in mesophyll cells,and defective chloroplast development.At 25?,wsl887 showed white-stripe phenotype,and the content of photosynthetic pigment in leaves increased,which was significantly different from the wild type.At 30?,wsl887 showed normal green leaf phenotype,and there was no significant difference in leaf photosynthetic pigment content between wsl887and wild type.3.There were significantly different in wsl887 that the expressions of genes related to chlorophyll synthesis,chloroplast development,photosynthesis and mitochondrial electron transport compared under different temperatures.At 20?,there was no significant difference in the expression of chlorophyll synthesis genes in wsl887compared with wild-type.However,the expression of photosynthesis-related genes included psa A,psb A,rbc S,rbc L,CAB1R and CAB2R were significantly decreased.Interestingly,the expression of genes in the mitochondrial electron transport complex(including cob,nad2,nad4,nad5,cox1 and cox2)were significantly increased.At30?,the expression of chlorophyll synthesis genes in wsl887 was significantly increased except for CHLD.The expression of cytoplasmic encoding genes(psa A,psb A and rbc L)were significantly decreased,while the expression levels of nuclear encoding genes(CAB1R,CAB2R and rbc S)were significantly increased.But,the expression of genes in the mitochondrial electron transport complex were significantly reduced.4.The phenotype of wsl887 is controlled by a pair of recessive nuclear genes.The wsl887 were located between RM262 and RM5427 on chromosome 2,about 743.6 KB region including 63 candidate genes.The subcellular localization prediction of 19 genes were predicted to be located in chloroplasts by https://www.genscript.com,involved WSL4(LOC?Os02g35750)have been cloned.However,it showed that WSL4 gene had no base mutation by sequence analysis in the mutant WSL887.The mutant phenotype and related gene expression of WSL4 were different from those of this study.These results indicated that WSL887 might be a new temperature-sensitive white stripe green gene.5.wsl887 has great application value in two-line breeding system of rice.A new photo-thermo sensitive genic male sterile(PTGMS)line carrying white stripe to green marker was obtained by crossing wsl887 with PTGMS line and adopting genealogical breeding,which laid the material foundation for the application of this mutant in two-line male sterile lines of rice. |
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