Agrogenomics Research Center, National Institute of Agrobiological Sciences, 305-8602 Tsukuba, Japan;
Independent HEISENBERG Research Group Plant Architecture, Leibniz Institute of Plant Genetics and Crop Plant Research, 06466 Gatersleben, Germany.
Proc Natl Acad Sci U S A. 2019 Mar 12;116(11):5182-5187. doi: 10.1073/pnas.1815465116. Epub 2019 Feb 21.
Floret fertility is a key determinant of the number of grains per inflorescence in cereals. During the evolution of wheat ( sp.), floret fertility has increased, such that current bread wheat () cultivars set three to five grains per spikelet. However, little is known regarding the genetic basis of floret fertility. The locus () is shown here to be an important contributor to floret fertility. evolved in the Triticeae through gene duplication. The gene, which encodes a homeodomain leucine zipper class I (HD-Zip I) transcription factor, was expressed most abundantly in the most apical floret primordia and in parts of the rachilla, suggesting that it acts to inhibit rachilla growth and development. The level of expression has decreased over the course of wheat evolution under domestication, leading to the production of spikes bearing more fertile florets and setting more grains per spikelet. Genetic analysis has revealed that the reduced-function allele contributes to the increased number of fertile florets per spikelet. The RNAi-based knockdown of led to an increase in the number of both fertile florets and grains in hexaploid wheat. Mutants carrying an impaired allele out-yielded WT allele carriers under field conditions. The data show that gene duplication generated evolutionary novelty affecting floret fertility while mutations favoring increased grain production have been under selection during wheat evolution under domestication.
小花育性是谷类作物每花序粒数的关键决定因素。在小麦（sp.）的进化过程中，小花育性增加，使得当前的面包小麦（）品种每小穗设置三到五个粒。然而，小花育性的遗传基础知之甚少。本研究表明，位点（）是小花育性的重要贡献者。通过基因复制在小麦族中进化而来。该基因编码一个同源域亮氨酸拉链类 I（HD-Zip I）转录因子，在最顶端的小花原基和穗轴的某些部位表达最丰富，表明它抑制穗轴的生长和发育。在小麦驯化过程中，随着基因的进化，的表达水平降低，导致产生具有更多育性小花的穗，并使每小穗产生更多的粒。遗传分析表明，低功能等位基因 有助于增加每小穗的育性小花数。基于 RNAi 的 基因敲低导致六倍体小麦中育性小花和粒数的增加。在田间条件下，携带功能受损 等位基因的突变体比 WT 等位基因携带者的产量更高。数据表明，基因复制产生了影响小花育性的进化新颖性，而有利于增加粒产量的突变在驯化过程中受到了选择。
