The <i>SEP</i> homologous gene <i>TEMARY</i> regulates inflorescence phenotypes in <i>Hydrangea Macrophylla</i>

Most <i>Hydrangea</i> species have inflorescences composed of two types of flowers: decorative flowers with showy sepals and plain nondecorative flowers. In wild plants of <i>Hydrangea macrophylla</i>, 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 <i>SEPALLATA</i> (<i>SEP)</i> homologous gene as a candidate gene, named <i>TEMARY</i>. We analyzed the genome sequences of <i>TEMARY</i> using several cultivars. The results revealed that the <i>H. macrophylla</i> 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 <i>TEMARY</i> 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 <i>TEMARY</i> normally. These results suggest that <i>TEMARY</i> controls the inflorescence type and that mutations in this gene cause the mophead phenotype.