The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Hebrew University of Jerusalem, P.O. Box 12, 7610001, Rehovot, Israel.
School of Plant Sciences and Food Security, Tel Aviv University, 6997801, Tel Aviv, Israel.
Theor Appl Genet. 2019 Aug;132(8):2353-2365. doi: 10.1007/s00122-019-03358-5. Epub 2019 May 11.
Wild emmer allele of GNI-A1 ease competition among developing grains through the suppression of floret fertility and increase grain weight in tetraploid wheat. Grain yield is a highly polygenic trait determined by the number of grains per unit area, as well as by grain weight. In wheat, grain number and grain weight are usually negatively correlated. Yet, the genetic basis underlying trade-off between the two is mostly unknown. Here, we fine-mapped a grain weight QTL using wild emmer introgressions in a durum wheat background and showed that grain weight is associated with the GNI-A1 gene, a regulator of floret fertility. In-depth characterization of grain number and grain weight indicated that suppression of distal florets by the wild emmer GNI-A1 allele increases weight of proximal grains in basal and central spikelets due to alteration in assimilate distribution. Re-sequencing of GNI-A1 in tetraploid wheat demonstrated the rich allelic repertoire of the wild emmer gene pool, including a rare allele which was present in two gene copies and contained a nonsynonymous mutation in the C-terminus of the protein. Using an F population generated from a cross between wild emmer accessions Zavitan, which carries the rare allele, and TTD140, we demonstrated that this unique polymorphism is associated with grain weight, independent of grain number. Moreover, we showed, for the first time, that GNI-A1 proteins are transcriptional activators and that selection targeted compromised activity of the protein. Our findings expand the knowledge of the genetic basis underlying trade-off between key yield components and may contribute to breeding efforts for enhanced grain yield.
野生二粒小麦 GNI-A1 等位基因通过抑制小花育性和增加四倍体小麦粒重来缓解发育中籽粒间的竞争。粒重是一个高度多基因性状，由单位面积的粒数以及粒重决定。在小麦中，粒数和粒重通常呈负相关。然而，两者之间权衡的遗传基础大多未知。在这里，我们使用硬质小麦背景下的野生二粒小麦导入系精细定位了一个粒重 QTL，并表明粒重与 GNI-A1 基因有关，该基因为小花育性的调节因子。对粒数和粒重的深入分析表明，野生二粒小麦 GNI-A1 等位基因对远部小花的抑制作用导致基部和中部小穗中近部籽粒的重量增加，这是由于同化产物分布的改变。对四倍体小麦中 GNI-A1 的重测序表明，野生二粒小麦基因库具有丰富的等位基因库，包括一个罕见的等位基因，该基因存在于两个基因拷贝中，并且在蛋白质的 C 末端含有一个非同义突变。使用来自携带罕见等位基因的野生二粒小麦品种 Zavitan 和 TTD140 之间杂交产生的 F 群体，我们证明了这种独特的多态性与粒重有关，与粒数无关。此外，我们首次表明，GNI-A1 蛋白是转录激活因子，选择针对的是蛋白活性受损。我们的研究结果扩展了对关键产量构成因素之间权衡的遗传基础的认识，并可能有助于提高粒重的育种工作。
