Segami Shuhei, Yamamoto Tatsuya, Oki Katsuyuki, Noda Tomonori, Kanamori Hiroyuki, Sasaki Harumi, Mori Satomi, Ashikari Motoyuki, Kitano Hidemi, Katayose Yuichi, Iwasaki Yukimoto, Miura Kotaro
Fukui Prefectural University, Faculty of Biotechnology, 4-1-1 Kenjojima, Matsuoka, Eiheiji-cho, Yoshida-gun, Fukui, 910-1195, Japan.
Japan Society for the Promotion of Science, Chiyoda-ku, Tokyo, 102-8472, Japan.
Rice (N Y). 2016 Dec;9(1):34. doi: 10.1186/s12284-016-0109-2. Epub 2016 Jul 25.
Grain size is an important trait that affects rice yield. Although many genes that contribute to grain size have been cloned from mutants or by quantitative trait locus (QTL) analysis based on bi-parental mapping, the molecular mechanisms underlying grain-size determination remain poorly understood. In this study, we identified the lines with the largest grain size and detected novel QTLs affecting the grain size.
We screened the National Institute for Agrobiological Sciences Genebank database and identified two rice lines, BG23 with the widest grain and LG10 with the longest grain. Using these two lines, we performed QTL analysis for grain size. Eight QTLs were detected during the QTL analyses using F2 populations derived from crosses between the large-grain lines BG23 or LG10 and the middle-size grain cultivars Nipponbare and Kasalath. Both BG23 and LG10 possessed large-grain alleles of four major QTLs: GW2, GS3, qSW5/GW5, and GW8. Other three minor QTLs were derived from BG23. However, these QTLs did not explain the differences in grain size between these two lines. Additionally, four QTLs for grain length or width were detected in an F2 population derived from a cross between BG23 and LG10; this population lacked the strong effects of the four major QTLs shared by both parent plants. Of these newly detected QTLs, the effects of two QTLs, GL3b and GL6, were confirmed by progeny testing. Comparison of the length of inner epidermal cells in plants homozygous for BG23 and LG10 alleles indicated that GL3b and GL6 genes regulate cell elongation and cell division, respectively.
In this study, we detected 12 loci including 14 QTLs regulating grain size from two lines with largest grains available in Japanese stock. Of these loci, we confirmed the effect of two gene loci and mapped their candidate region. Identification of novel genes regulating grain size will contribute to our understanding of the molecular mechanisms controlling grain size.
粒型是影响水稻产量的一个重要性状。尽管已经从突变体中克隆出许多影响粒型的基因，或通过基于双亲图谱的数量性状位点（QTL）分析鉴定出这些基因，但粒型决定的分子机制仍知之甚少。在本研究中，我们鉴定出粒型最大的品系，并检测到影响粒型的新QTL。
我们筛选了日本农业生物科学研究所基因库数据库，鉴定出两个水稻品系，粒宽最宽的BG23和粒长最长的LG10。利用这两个品系，我们对粒型进行了QTL分析。在使用大粒品系BG23或LG10与中粒品种日本晴和卡萨拉斯杂交得到的F2群体进行的QTL分析中，检测到8个QTL。BG23和LG10都拥有四个主要QTL的大粒等位基因：GW2、GS3、qSW5/GW5和GW8。另外三个次要QTL来自BG23。然而，这些QTL并不能解释这两个品系之间粒型的差异。此外，在BG23和LG10杂交得到的F2群体中检测到四个控制粒长或粒宽的QTL；该群体缺乏双亲共有的四个主要QTL的强烈效应。在这些新检测到的QTL中，通过后代检测证实了两个QTL（GL3b和GL6）的效应。对BG23和LG10等位基因纯合植株的内表皮细胞长度进行比较表明，GL3b和GL6基因分别调控细胞伸长和细胞分裂。
在本研究中，我们从日本种质中两个粒型最大的品系中检测到12个位点，包括14个调控粒型的QTL。在这些位点中，我们证实了两个基因位点的效应并定位了它们的候选区域。鉴定调控粒型的新基因将有助于我们理解控制粒型的分子机制。
