Zhao Yanming, Ma Xiaojie, Zhou Miaomiao, Wang Junyan, Wang Guiying, Su Chengfu
College of Agronomy, Qingdao Agricultural University, Qingdao, China.
Shandong Provincial Key Laboratory of Dryland Farming Technology, Qingdao Agricultural University, Qingdao, China.
Front Plant Sci. 2022 Jun 30;13:935654. doi: 10.3389/fpls.2022.935654. eCollection 2022.
Kernel size is an important agronomic trait for grain yield in maize. The purpose of this study was to validate a major quantitative trait locus (QTL), , which was identified in the F and F populations from a cross between the maize inbred lines SG5/SG7 and to predict candidate genes for kernel width (KW) in maize. A major QTL, , was mapped in multiple environments in our previous study. To validate and fine map , near-isogenic lines (NILs) with 469 individuals were developed by continuous backcrossing between SG5 as the donor parent and SG7 as the recurrent parent. Marker-assisted selection was conducted from the BCF generation with simple sequence repeat (SSR) markers near . A secondary linkage map with four markers, PLK12, PLK13, PLK15, and PLK17, was developed and used for mapping the locus. Finally, was mapped between the PLK12 and PLK13 intervals, with a distance of 2.23 cM to PLK12 and 0.04 cM to PLK13, a confidence interval of 5.3 cM and a phenotypic contribution rate of 23.8%. The QTL mapping result obtained was further validated by using selected overlapping recombinant chromosomes on the target segment of maize chromosome 3. Transcriptome analysis showed that a total of 12 out of 45 protein-coding genes differentially expressed between the two parents were detected in the identified physical interval by blasting with the Zea_Mays_B73 v4 genome. GRMZM2G083176 encodes the Niemann-Pick disease type C, and GRMZM2G081719 encodes the nitrate transporter 1 (NRT1) protein. The two genes GRMZM2G083176 and GRMZM2G081719 were predicted to be candidate genes of Reverse transcription-polymerase chain reaction (RT-qPCR) validation was conducted, and the results provide further proof of the two candidate genes most likely responsible for . The work will not only help to understand the genetic mechanisms of KW in maize but also lay a foundation for further cloning of promising loci.
籽粒大小是玉米产量的一个重要农艺性状。本研究的目的是验证一个主要数量性状位点（QTL），该位点是在玉米自交系SG5/SG7杂交的F和F群体中鉴定出来的，并预测玉米籽粒宽度（KW）的候选基因。在我们之前的研究中，一个主要的QTL在多个环境中被定位。为了验证和精细定位该QTL，以SG5为供体亲本、SG7为轮回亲本，通过连续回交培育了469个个体的近等基因系（NILs）。从BCF代开始，利用位于该QTL附近的简单序列重复（SSR）标记进行标记辅助选择。构建了一个包含四个标记PLK12、PLK13、PLK15和PLK17的二级连锁图谱，并用于定位该QTL位点。最终，该QTL被定位在PLK12和PLK13区间之间，与PLK12的距离为2.23 cM，与PLK13的距离为0.04 cM，置信区间为5.3 cM，表型贡献率为23.8%。通过使用玉米3号染色体目标区段上选定的重叠重组染色体，进一步验证了获得的QTL定位结果。转录组分析表明，通过与玉米B73 v4基因组进行比对，在鉴定出的物理区间内，共检测到45个在两个亲本之间差异表达的蛋白质编码基因中的12个。GRMZM2G083176编码尼曼-匹克病C型，GRMZM2G081719编码硝酸盐转运蛋白1（NRT1）。GRMZM2G083176和GRMZM2G081719这两个基因被预测为该QTL的候选基因。进行了逆转录聚合酶链反应（RT-qPCR）验证，结果进一步证明了这两个最有可能导致该QTL的候选基因。这项工作不仅有助于了解玉米KW的遗传机制，也为进一步克隆有前景的基因座奠定了基础。
