| Rice (Oryza sativa L.) is a pivotal cereal crop around the world. The requirement for the nutritional value of rice has been higher. Rice nutrition quality includes protein, fat, vitamins, traces minerals, and etc. Vitamin E, a very important antioxidant in organisms, is an essential nutrient for people and can only be taken from the food. Investigating the genetic basis of vitamin E and the mechanism underlying vitamin E synthesis, would be a great use in increasing the vitamin E content and improving the nutrition quality of rice.In this study, two recombinant inbred lines populations were used for identifying the QTLs controlling the content and composition of tocochromanol in brown rice. The relationship between the QTL identified and homologous genes involved in the vitamin E synthesis in rice was analyzed. The main results are as follows:1. Using a recombinant inbred line (RIL) population derived from Zhenshan97and Nanyangzhan, QTL mapping for8isomers (a,(3, y,8-tocopherol and α,β,γ,δ-tocotrienol) content and a/y of vitamin E in brown rice was conducted in2010and2011. In total,27QTLs were identified in two years and distributed on the chromosome1,2,3,4,5,6,7,8and10. Among them, five major QTLs were co-located to the interval RM497-RM166as a cluster on chromosome2, and repeatly detected in two years, with the phenotypic variation explained varying from10.9%to58.0%. Among that, the allele of QTL controlling y-isomers content from Zhenshan97had a positive effect, while the alleles of QTL controlling a-isomers and a/y from Nanyangzhan had positive effects.2. Using a RIL population derived from Zhenshan97and Delong208, QTL mapping for controlling8isomers content and a/y of vitamin E in brown rice content was performed in2011.4QTLs were identified, including a QTL for a-tocopherol content on chromosome1, a QTL for y-tocopherol content on chromosome2, and two QTLs for δ-tocotrienol on chromosome2and6, with the phenotypic variation explained varying between8%and10%. Only the allele for y-tocopherol from Delong208has a positive effect, while the others all from Zhenshan97.3. The homologous genes involved in vitamin E biosynthesis in rice had been identified using the information of the cloned vitamin E biosynthesis genes in Arabidopsis. Comparing the position of the homologous genes in rice and the QTLs detected in the study, we found that the gene OsyTMT was about1.3Mb away from the mark RM497on the chromosome2, next to the major QTL cluster identified in zhenshan97/Nanyangzhan RIL, and the qVE-2from Zhenshan97/Delong208RIL; OsHPT and OsHGGT were co-localized with qT3y6a on chromosome6, and OsHPPD was co-localized with qVE-2-1on chromosome2.4. Using the Nipponbare genome as a reference, the alleles of OsyTMT (LOC_Os02g47310) in Zhenshan97and Nanyangzhan were sequenced and compared. Results showed that the structure of the two alleles was similar and the length of their CDS was same. The CDS of Nanyangzhan was the same to that of Nipponbare, while two SNPs in the second and fourth extron, respectively, were exsited in Zhenshan97, compared with that of Nanyangzhan. Meanwhile, the two SNPs resulted in the amino acids transition, the first SNP transforming the Val in Nanyangzhan into Ile in Zhenshan97, while the second the Arg in Nanyangzhan into Gly in Zhenshan97. Other substitution, insertion and deletion mutation (InDel) were distributed in the introns and the2kb promoter regions of5’end. Some large variations were the266bp InDel in the first intron, and10bp and3bp InDel in the-120bp and-160bp of the promoter regions.5. Homology and phylogeny analysis of y-TMT amino acid sequences were conducted. The results showed that the sequence identity of Rice OsyTMT (LOC_Os02g47310) with Arabidopsis γ-TMT was about61%. |
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