Most Hydrangea species have inflorescences composed of two types of flowers: decorative flowers with showy sepals, and plain non-decorative flowers. In wild plants of H. macrophylla, the decorative flowers are located at the periphery of the corymb, resulting in the lacecap phenotype. However, after the discovery of the mophead phenotype, in which decorative flowers are borne not only at the periphery but also on the entire inflorescence, it developed remarkably as a garden plant. In this study, we aimed to identify the gene controlling the inflorescence type and the mutations causing the mophead phenotype. Linkage analyses identified a SEPALLATA (SEP) homologous gene as a candidate gene, named TEMARY. We analyzed the genome sequences of TEMARY using several cultivars. The results revealed that the H. macrophylla cultivars had three types of loss-of-function alleles, and that the locus of the mophead cultivars consisted of only loss-of-function alleles. The phenotypes of 27 mophead cultivars could be explained by three types of loss-of-function TEMARY alleles. RNA-seq analysis and qRT-PCR analysis using two bud sport mutant lines related to the inflorescence type revealed that mophead mutants did not express TEMARY normally. These results suggest that TEMARY controls the inflorescence type and that mutations in this gene cause the mophead phenotype.

中文翻译：

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SEP 同源基因 TEMARY 调控 H. macrophylla 的花序表型


大多数绣球花物种的花序由两种类型的花组成：带有艳丽萼片的装饰性花和普通的非装饰性花。在 H. macrophylla 的野生植物中，装饰花位于 corymb 的外围，导致花边帽表型。然而，在发现拖把头表型后，其中装饰花不仅在外围，而且在整个花序上，它作为一种园林植物得到了显着发展。在这项研究中，我们旨在确定控制花序类型的基因和导致拖头花表型的突变。连锁分析确定 SEPALLATA （SEP） 同源基因为候选基因，命名为 TEMARY。我们使用几个栽培品种分析了 TEMARY 的基因组序列。结果表明，H. macrophylla 品种具有 3 种类型的功能丧失等位基因，而拖把头品种的基因座仅由功能丧失等位基因组成。27 个拖把头品种的表型可以用 3 种功能丧失的 TEMARY 等位基因来解释。使用与花序类型相关的两个芽运动突变体系的 RNA-seq 分析和 qRT-PCR 分析显示，拖头突变体不正常表达 TEMARY。这些结果表明，TEMARY 控制花序类型，并且该基因的突变导致拖头表型。