Rice Heading Date Allele Genovariation And QHD3 Pleiotropic Analysis

Rice(Oryza sativa L.)is the most important ration crop in China,and more than 60% of the country's residents rely on rice as their staple food.Heading date(HD)is one of the important agronomic traits of rice.It plays an important role in the high and stable yield of the variety and is related to the food problem of the world's population.Accurate control of heading date is the key to successful rice reproduction and one of the important breeding goals.The Single Segment Substitution Line(SSSL),developed based on Maker-Assisted Selection(MAS),is a new type of subpopulation.It is an ideal experiment material for studying genetic variation and epistasis analysis..This study includes three main areas.1.Genetic differentiation and expression analysis of heading date genes on replacement segments of the rice single segment substitution lines established in this laboratory.2.Pleiotropic analysis of QTL qHD3 using WY70 which was an SSSL with Huajingxian74(HJX74)as the genetic background and Lemont as the donor parent.3.Genome-wide transcriptome analysis of WY70 and HJX74 on heading date,and new heading date genes predicting.Using 4 SSSLs and recipient parent HJX74 as experimental materials,combining the heading date phenotype of 2018 and 2019,variations of the heading alleles on the substitution segments were studied,including CDS sequences,amino acid sequences,amino acid hydrophobicity,amino acid physicochemical properties.The 4 SSSLs were WY18(W06-15-18-3-11),WY24(W08-16-3-2),WY26(W11-15-7-1-1),WY70(W23-03-08-9-1),respectively.Using SSSL WY70 with the substitution fragment W23-03-08-9-1,a rice heading QTL qHD3 was detected which contained a known heading gene OsMADS50.The WY70 with QTLqHD3 not only showed extremely early maturity,but also had the effects of reducing plant height,increasing kernel length,and decreasing thousand-grain weight.In our previous study,MADS-box gene OsMADS50 which was a heading date gene involved in the Ehd1-Hd3a/RFT1 flowering regulatory pathway was rest in qHD3 target chromosomal region.At the same time,the high expression of GS3 increased grain length and decreased the thousand grain weight of rice.Transcriptome sequencing was performed using leaves of HJX74 and WY70 at different dates after sowing.By analyzing the expression profiles of WY70 and HJX74,combined with the information of 50 rice heading date QTLs,we identified 15 differential genes related to heading date.We further performed qRt-PCR to verify the 15 genes.Compared with HJX74,the expression levels of LOC_Os02g14990,LOC_Os02g15120,LOC_Os06g35850,LOC_Os07g41370,LOC_Os07g42610,LOC_Os08g41960,LOC_Os10g42850,LOC_Os11g02670,and LOC_Os11g45850 were significantly increased in WY70.In contrast,the expression levels of LOC_Os02g36924,LOC_Os04g31804,and LOC_Os06g40330 were significantly suppressed,indicating that OsMADS50 is their upstream regulatory gene.The expression levels of LOC_Os05g50350,LOC_Os07g43580,and LOC_Os11g45740 did not change significantly,indicating that OsMADS50 is downstream or parallel to it.The 15 genes were greatly enriched the rice heading gene database.