Fine Mapping Of A Yellow Green Leaf Gene In Rice And Screening Of Crude Fat Content In Rice Grains

Part I.Fine mapping of yellow green leaf gene in riceThere are many varieties of leaf color mutants in rice,which not only provide rich ornamental value and research value,but also can be used to improve and develop new germplasm resources,enhance the economic value and quality of varieties.Photosynthesis of plants is inseparable from chlorophyll.We usually think that the plants with abnormal chlorophyll content are unfavorable to their growth and development,thus affecting their yield and quality.However,some studies have shown that the lack of chlorophyll content will lead to better taste of their seeds.(1)In this paper,a yellow green leaf mutant of rice variety RX69 was obtained by physical mutagenesis,and the gene controlling the phenotype was located by mapping based cloning: The leaf color of w81 mutant turned yellow green before heading stage,and returned to green with the beginning of heading stage.The chlorophyll content decreased significantly at the three leaf stage and was almost the same as that of the wild type at heading stage.The yellow green leaf phenotype resulted in loose arrangement of thylakoid lamellae in chloroplast of rice leaves;The expression of chloroplast development genes was down regulated.There was no significant difference in 1000 grain weight,number of spikelets per spike and plant height between the mutant and the wild type due to the restoration of green leaf at late stage.(2)Genetic analysis showed that the yellow green leaf phenotype of w81 was controlled by a single recessive gene.The 37.5kb region between s5-19 and s5-3 was located by map based cloning.The interval consists of six hypothetical open reading frames(ORFs).Genome sequencing analysis showed that in the fifth ORF(LOC)＿Os05g50980)carries a single nucleotide transition(T→A)at the 7bp position in front of the sixth exon.LOC＿Os05g50980contains 11 exons and encodes a set domain protein with 500 amino acids.It is a Pap family protein that affects NEP process,named ospap7.(3)Ospap7 was located in chloroplast.RT-PCR results showed that ospap7 had the highest expression in leaves.In the mutant,the expression level of chloroplast located nuclear coding genes was significantly decreased,PEP dependent gene expression was significantly down regulated,and NEP dependent gene expression was significantly up-regulated,which suggested that the loss of ospap7 function changed the expression of plastid and chloroplast nuclear coding genes,and impaired the activity of PEP complex.2.Screening of crude fat content in Rice.Part II.Screening of rice crude fat content resources in rice grainsWith the improvement of people’s living standards,rice quality has become an important breeding goal.Fat plays an important role in rice quality,but there are few studies on the fat content of rice at present.Accurate identification of important traits such as fat content of germplasm resources can lay a foundation for exploring excellent germplasm and alleles.In this paper,the crude fat content of 222 rice germplasm resources from all over China was measured and analyzed:The average content of crude fat in 222 rice germplasm resources was 2.43%,with a range of 0.82%--4.14%.The fat content of most varieties ranged from 2% to 2.5%.The crude fat content of zixiangnuo 1 and Zhendao 2 was more than 4%,which was 4.14%,while that of Wuyunjing 7,Yanjing 16 and Ning 88 was less than 1%,which was 0.82%,0.94% and0.98%,respectively.The standard error of the two repetitions of the germplasm resources tested in this study is between 0.001-0.090.For the resources with large standard error,we repeated the test twice to ensure the accuracy of the data.The average content of crude fat was 2.73% in indica rice and 2.40% in japonica rice.Among the indica rice varieties,the crude fat content of xiangwanxian 3,Huanhui 422 and Taichung Xianxuan 220 was lower than 1%;The crude fat content of EZHONG 5 and Youzhan 8 was higher than 3.60%.In japonica rice,Wanjing 2018 and Yandao 93015 had lower crude fat content;Zixiangnuo No.1 and Zhendao No.2 had the highest crude fat content(more than 4%),which were the special resources with high fat content.The average content of crude fat in glutinous rice and non glutinous rice was 2.44% and 2.42%,respectively;From the regional point of view,the average crude fat content of Shandong rice varieties was2.82%,Guizhou 2.79%,Anhui 2.61%,Heilongjiang 2.53% and Jiangsu 2.39%,Zhejiang2.53%;In Jiangsu Province,the highest crude fat content was 2.79% in Nantong,and the lowest was 2.18% in Suqian.In terms of years,the average crude fat content of rice varieties approved before 2000 was 2.39%,and the average crude fat content of rice varieties approved after 2000 was 2.30%.In this study,the number of varieties in different subspecies,regions and other places is quite different,and the analysis results may be different from the predecessors,and the next will continue to expand the variety types.The number of rice varieties in different subspecies and regions measured in this study is quite different,and the analysis results may be different from those of previous studies.In the future,we will continue to expand the variety types.The results provide a basis for the improvement of rice crude fat content breeding and gene mining in the future.