Institute for Plant Genetics, Heinrich-Heine University, Universitätsstraße 1, D-40225 Düsseldorf, Germany;
Department of Plant Developmental Biology, Max Planck Institute for Plant Breeding Research, Carl-von-Linne-Weg 10, D-50829 Cologne, Germany.
Proc Natl Acad Sci U S A. 2021 Feb 23;118(8). doi: 10.1073/pnas.2011779118.
Inflorescence architecture dictates the number of flowers and, ultimately, seeds. The architectural discrepancies between two related cereals, barley and wheat, are controlled by differences in determinacy of inflorescence and spikelet meristems. Here, we characterize two allelic series of mutations named () and () that convert barley indeterminate inflorescences into wheat-like determinate inflorescences bearing a multifloreted terminal spikelet and spikelets with additional florets. / encodes an APETALA2-like transcription factor (HvAP2L-H5) that suppresses ectopic and precocious spikelet initiation signals and maintains meristem activity. HvAP2L-H5 inhibits the identity shift of an inflorescence meristem (IM) to a terminal spikelet meristem (TSM) in barley. Null mutations in lead to fewer spikelets per inflorescence but extra florets per spikelet. In wheat, prolonged and elevated AP2L-A5 activity in mutants delays but does not suppress the IM-TSM transition. We hypothesize that the regulation of orthologs and downstream genes contributes to the different inflorescence determinacy in barley and wheat. We show that AP2L-5 proteins are evolutionarily conserved in grasses, promote IM activity, and restrict floret number per spikelet. This study provides insights into the regulation of spikelet and floret number, and hence grain yield in barley and wheat.
花序结构决定了花的数量，最终决定了种子的数量。两种相关谷物——大麦和小麦的结构差异是由花序和小穗分生组织的确定性差异控制的。在这里，我们描述了两个等位基因系列的突变，分别命名为 () 和 ()，它们将大麦的不定花序转化为小麦状的定序花序，具有多小花的顶端小穗和具有额外小花的小穗。/ 编码一个 APETALA2 样转录因子（HvAP2L-H5），它抑制异位和早熟小穗起始信号，维持分生组织活性。HvAP2L-H5 抑制大麦花序分生组织（IM）向顶端小穗分生组织（TSM）的身份转变。/ 的缺失突变导致每个花序的小穗减少，但每个小穗的小花增多。在小麦中，/ 突变体中 AP2L-A5 活性的延长和升高延迟但不能抑制 IM-TSM 转变。我们假设 及其下游基因的调控导致了大麦和小麦不同的花序确定性。我们表明，AP2L-5 蛋白在禾本科植物中是进化保守的，促进 IM 活性，并限制每个小穗的小花数量。本研究为大麦和小麦小穗和小花数量以及籽粒产量的调控提供了新的见解。
