| Rice,wheat and corn are known as the most important food crops in the world.In addition,rice became a model plant of gramineous plants,because it's genome are relatively small compared with other gramineous plants.Now,the rice genome has been sequenced completely.The studies of genes in rice may contribute to the studies of other crops.Construction of rice mutant libraries is the best way to study the function of genes in rice.The physical and chemical mutagenesis has high mutation frequency.The phenotypes of leaf color mutant can be observed in the seeding stage.These mutant can be used for the dissection of plant chloroplast structure,function,genetic,differentiation and development,chlorophyll biosynthesis and hormone adjustment.1.The main result of mutant identification:In the summer of 2013,we identified the M4 generation of the mutant pools with W017,NJ11,12Xinuo,Xia 951,IRAT118 varieties as the background material by chemical mutagenesis.We obtained 53 mutants of rice and measured the agronomic traits such as plant height,flag leaf length,width,panicle length,number of effective panicles per plant of 12 mutants.The study made actively preparing for the next research.2.The main results of a yellow-green leaf mutant T113:(1)In this study,the yellow-green leaf mutant T113 was isolated from a T-DNA mutant pool with Dongjin varieties as the background material.The mutant showed a yellow-green leaf phenotype in whole developing stage.Meanwhile,the plant height of the mutant was lower than that of the wild type and is only 69%of the wild type.The heading date of mutant was delayed in about a week.The panicles length of mutant T113 is shorter than wild type.The seed setting rate and 1000 grain weight decreased in mutant too.We also found that there are different degrees of difference of flag leaf length,width,tiller number between the mutant and the wild type.(2)Compare to the wild type,we found the contents of chlorophyll a,chlorophyll b and carotenes were significantly reduced in the field.Most interesting is that the variance of these pigment content in heading stage was noteworthy smaller than seedling period.In summary,the difference of pigment content and phenotype was relatively consistent.Through the experiment of temperature sensitivity,we found that the mutant phenotype is not affected by temperature.The T113 mutant exhibited yellow green leaf phenotype at 20 °C,23 °C~26 °C and 30 °C,the pigment contents was significantly lower compared to the wild ty'pe.So we get a conclusion that T1 13 mutant is not affected by temperature.(3)Ultrastructural analysis of chloroplasts showed the chloroplast of mutant was brighter than wild type,the thylakoid arranged more loose and got more osmiphilic body in mutant.The result may be associated with the mutant developed an abnormal chloroplast structures.(4)Quantitative RT-PCR analysis of genes associated with chlorophyll biogenesis and genes associated with chloroplast development in wild type and T113 mutant.The result showed that the expression of the genes associated with chlorophyll biogenesis in T113 mutant was lower than wild type.In addition,the expression of PsaA,PsaB,PsbA,RbcL which participate in the chloroplast photosynthetic system increased.But NDH2,NDH4 and RpoA expressed lower than wild type.(5)We used the F1 and F2 population of the mutant T113 and wild type Dongjin to conduct a genetic analysis.The result showed that the mutant phenotype was controlled by a pairs of recessive genes.Then we used the F2 population of the mutant T113 and Indica rice varieties N22 to conduct a fine mapping and the result showed that it was located at the chromosome 2,between indel marker CX2 and JX18.There were 79kb between these two markers and 12 genes were in this region.We sequenced these genes and found that Os02g0744900 got a single base mutation in the CDS.Os02g0744900 may be the candidate gene of T113 mutant.The gene is 2577 bp,encoding a geranylgeranyl reductase. |
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