Map-based cloning and functional validation of a QTL for grain size in wheat

QTL Q.Tgw.ipk-7D增加了小麦的籽粒大小，对总粒重和收获指数也有正效应。通过遗传方法，研究表明，一种隐性遗传的孟德尔基因导致了这些效应。我们的目标是对影响籽粒大小的QTL Q.Tgw.ipk-7D的小麦基因进行分子鉴定和功能验证。QTL区间通过精细定位和与水稻和Brachypodium disachyon的共性研究发现，该区域具有良好的共性。感兴趣的区域分别包含36个水稻基因和42个青冈属基因。其中可能是编码AP2结构域蛋白的QTL Q.Tgw.ipk-7D的候选基因。进一步的精细定位有望缩小QTL Q.Tgw.ipk-7D可能候选基因的范围。因此，正在进行的基于图谱的克隆方法将继续进行，获得的候选基因将在稳定转化的小麦品系中进行功能测试。QTL Q.Tgw.ipk-7D的分子鉴定将为小麦籽粒大小的遗传调控提供新的见解，并将成为第一个在小麦中报道的克隆的QTL。

QTL Q.Tgw.ipk-7D increases grain size in wheat and also has positive effects on total grain mass and harvest index. By genetic methods, it was shown that a Mendelian gene inherited in recessive fashion is causing these effects. Our aim is the molecular identification and functional verification of the wheat gene underlying the QTL Q.Tgw.ipk-7D affecting grain size. The QTL interval was genetically delimited by fine mapping and synteny studies with rice and Brachypodium distachyon revealed a good synteny for the investigated region. The area of interest harbours 36 and 42 genes in rice and Brachypodium, respectively. Among them is a possible candidate gene for QTL Q.Tgw.ipk-7D encoding an AP2 domain containing protein. Further fine mapping is expected to narrow down the list of possible candidate genes for QTL Q.Tgw.ipk-7D. Therefore, the ongoing map based cloning approach is to be continued and obtained candidates are to be tested for their functionality in stably transformed wheat lines. The molecular identification of QTL Q.Tgw.ipk-7D will provide novel insight in the heritable regulators of grain size in wheat and would constitute the first cloned QTL reported in wheat.