芝麻粒重主效QTL qTGW11.1的精细定位与候选基因鉴定

Grain weight is one of the most important factors contributing to crop yield and it has been hotpoint to dissect the genetic basis and mechanism of grain weight in crops such as rice and maize. Sesame (Sesamum indicum L.) is an special traditional oil crop, but about 55% of its consumption depends on importation in China. It is a top urgent task to increase sesame yield for sesame researchers in a long term. Fine mapping QTLs and identifying the candidate genes of grain weight in sesame was of much significance for understanding the genetic basis and promoting the sesame high-yield breeding procedure. We have constructed a genetic population using two sesame accessions extremely differing from grain weight trait, and drawn a high density genetic linkage map. And then we found a major QTL named qTGW11.1, which was located at a 2.7 cM region markered by ZMM4664 and ZMM4663 on LG11。It could be detected under different trials explaining over 20% of phenotype variance. It is of great need to dissect the molecular basis of this major QTL. In this project, we aim to do the following experiments: (1) Fine mapping of qTGW11.1. Based on sesame genome sequence and biparental resequencing information, numerous markers were developed aiding to construct QTL-NIL and map the QTL into a 80 kb region. Candidate genes would be excavated through bioinformatical prediction, annotation and assortment. (2) Exploring the pivotal candidate genes. About ten genes would be selected according to the studies on grain weight related genes in the other plants, and then the coding region of these ten genes would be PCR-amplified from two parents and sequenced. Pivotal candidate genes of grain weight would be manifested by comparing the differences of coding domain sequence between two parents. (3) Identification of candidate genes by way of association analysis and gene expression, which would also help to reveal the variance characteristics of candidate genes among sesame germplasm resources and develop functional markers of grain weight and discover elite gene resources.The results will offer powerful guide to high-yield breeding and further characterization of gene function in sesame.

粒重是影响作物产量的重要因子，也是解析作物产量性状分子基础的研究热点。开展芝麻粒重QTL精细定位及候选基因鉴定，对揭示粒重分子基础、推动芝麻高产育种具有重要意义。前期已经构建了粒重遗传群体，绘制了高密度遗传图谱；对粒重QTL初定位，发现一个位于第11连锁群、标记间距约2.7cM的主效QTL，在2个环境中贡献率均大于20%，命名为qTGW11.1。本项目拟重点开展qTGW11.1精细定位和候选基因鉴定。首先基于芝麻基因组信息和亲本重测序信息，不断加密QTL区间标记、辅助选择构建大规模QTL-NIL群体，实现qTGW11.1精细定位（80kb以内），并预测粒重候选基因；比较候选基因编码区序列在双亲间的差异，确定2-3个关键基因；再通过候选基因关联分析和基因表达分析，进行候选基因鉴定，揭示粒重基因在芝麻种质资源中的变异特征，开发功能标记。研究结果将为芝麻粒重性状的遗传改良及分子解析提供理论指导。

粒重是影响作物产量的重要因子，也是解析作物产量性状分子基础的研究热点。开展芝麻粒重QTL精细定位及候选基因鉴定，对揭示粒重分子基础、推动芝麻高产育种具有重要意义。前期已经构建了粒重遗传群体，绘制了高密度遗传图谱；对粒重QTL初定位，发现一个位于第11连锁群、标记间距约2.7cM的主效QTL，在2个环境中贡献率均大于20%，命名为qTGW11.1。本项目拟重点开展qTGW11.1精细定位和候选基因鉴定。.本项目主要研究内容包括：（1）目标区间标记开发和QTL区间作图、BC2F1群体标记辅助选择及表型数据采集、和BC3F1群体构建；（2）BSA-seq、KASP标记开发与基因分型、QTL区间初步确定；（3）不同粒重亲本不同发育时期籽粒、蒴果皮的转录组分析、候选基因筛选及qPCR分析等。.重要结果与关键数据：（1）利用目标QTL区间开发的300多个多态性分子标记，结合亲本、F1和F2（J4F2）表型和基因型数据，完成对目标QTL qTWG11.1区间的局部遗传作图。将区间由2.735cM缩小至2.210cM (约330 Kb)，位于标记SmID28*和SmID47*之间。（2）基于F2群体BSA-seq分析和KASP基因分型结果析，在引物KASP-21017（NC_026145.1_17120043 ）和KASP-342（NC_026145.1_17329436）之间获得一个主效QTL，区间距离约209.3 Kb。生信分析发现，该区间有33个基因，初步分析约有14个可能的候选基因。（3）结合不同发育时期籽粒、蒴果皮的RNA-Seq转录组数据分析，筛选出在籽粒和果皮不同发育时期均上调表达的注释功能基因8个、均下调表达的注释功能基因15个。参考其他物种上已经发表的粒重及籽粒发育研究相关文献，筛选确定了6个粒重相关关键候选基因（DA1、ARF2、PGM、GST、PYL4、ALE2）。进一步利用亲本和F2群体极端单株的籽粒（3个发育时期）进行候选基因qPCR分析。结果初步揭示，基因DA1、PYL4、ALE2可能在芝麻粒重形成中发挥重要的正向调控作用；而PGM、GST基因则可能在芝麻粒重形成中发挥重要的负向调控作用。ARF2在芝麻粒重形成中发挥的作用则不明显。研究结果将为进一步开展芝麻粒重性状的遗传改良及分子解析提供功能标记和理论指导。