Allelic Variation And Regulatory Pathways Of DTH2 And Hd17 In Rice

Rice(Oryza sativa L.)is one of the most important food crops in the world.The heading date is an important agronomic trait that determines the adaptability of variety regions and seasons.Therefore,it has important theoretical significance and application value for allelic variation analysis of heading date genes.In this study,the single segment substitution lines(SSSL)of Asian cultivated rice,African cultivated rice and wild rice was used as the materials,and the phenotype analysis was carried out for four consecutive years.Through the sequence analysis of the DTH2 and Hd17 genes of different types of materials and the quantitative expression analysis of related genes,the alleles of these materials in DTH2 and Hd17 were determined,he expression analysis also confirmed the existence of new alleles,and analyzed the location of DTH2 gene and Hd17 gene in rice photoperiod regulation network and gene evolution relationship.The main results of this study are as follows:1、 Allelic variation of DTH2.Based on the performance of SSSL materials in the early and late season of Guangzhou for many years,and the sequence variation of these materials in the DTH2 gene,it was found that there were 4 alleles of DTH2 in these materials.The DTH2-1 allele is mainly present in japonica rice materials and is the result of G-A variation at 25 sites and G-T variation at 1721 sites(haplotype1).The DTH2-2 allele is mainly present in tropical japonica rice materials and is the result of G-A variation at 25 sites(haplotype2).The DTH2-3 allele is present in the wild rice material of indica rice.Although the C-T mutation occurred at 461 points and the T-C mutation occurred at 1,645 points,the mutations at these two points were both no change in phenotype,so it is the original type(haplotype3).The DTH2-4 allele is present in cultivated rice materials in Africa and is the result of the G-A mutation at 1744 sites(haplotype 4).Among them,DTH2-4,which is present in African cultivated rice,is a new allele found in this study.The G/A variant of its 1744 site leads to a functional variation in the spike stage and is a newly discovered functional site.2、The position and role of DTH2 in the control network of rice.Analysis of RT-PCR expression of four allele materials under LD and SD conditions shows that there is no significant difference in the expression of four alleles of DTH2,but it can lead to significant differences in the expression of Ehd1 gene.The results show that the different alleles of DTH2 lead to differences in the expression of Ehd1 gene through sequence differences rather than their own expression differences.Under LD conditions,DTH2 regulates the expression difference of downstream gene Hd3 a and RFT1 through the Ehd1 pathway,resulting in changes in the heading date of rice.3、Allelic variation of Hd17.Based on the performance of SSSL materials in the early and late season of Guangzhou for many years,and the sequence variation of these materials in the Hd17 gene,three alleles variants of Hd17 were found in these materials.The Hd17-1 allele is mainly present in japonica and tropical indica rice materials is the result of C-T variation at 3869 sites(haplotype1).The Hd17-2 allele is present in tropical japonica and indica rice materials and there is no functional sequence variation,which is the original type(haplotype2).Interestingly,although the Hd17 gene carried by African cultivated rice has a large difference in sequence(haplotype 4),the allele belongs to Hd17-2.Hd17-3 allele is present in wild rice and indica rice materials and are the result of C-T mutations at 2414 sites(haplotype3).Among them,the Hd17-3 allele carried by wild rice and indica rice is a new allele found in this study.The C/T mutation at the 2414 site leads to functional variation and is a new functional site.In addition,African cultivated rice carrying Hd17-2 allele is also the first discovery in this study.4、The position and role of Hd17 in the control network of rice.Analysis of RT-PCR expression of three allele materials under LD and SD conditions showed that there were significant differences in the expression of three alleles of Hd17 under LD conditions.Hd17 directly acts on Ghd7,promotes the expression of Ghd7,and regulates Ehd1 and Hd3 a / RFT1 through Ghd7,which eventually leads to changes the heading date of rice.In summary,the phenotypes and genotypes of the DTH2 and Hd17 genes were comprehensively analyzed using SSSL materials.New alleles and new functional sites were found in both DTH2 and Hd17 genes.At the same time,the position of these two genes in the rice regulation network and the regulation of downstream genes were further clarified.These results are of great theoretical and practical significance for improving the gene network for the regulation of rice and for the molecular design and breeding of rice.