# The SEP homologous gene TEMARY regulates inflorescence phenotypes in Hydrangea Macrophylla

## TL;DR

This study identifies the TEMARY gene as responsible for the mophead inflorescence phenotype in Hydrangea macrophylla, showing how mutations in this gene lead to changes in flower arrangement.

## Contribution

The study discovers TEMARY, a SEP homologous gene, as the key regulator of inflorescence type in Hydrangea macrophylla.

## Key findings

- Three types of loss-of-function TEMARY alleles were identified in mophead cultivars.
- Mophead mutants do not express TEMARY normally, as shown by RNA-seq and qRT-PCR analyses.
- The TEMARY gene locus in mophead cultivars consists only of loss-of-function alleles.

## Abstract

Most Hydrangea species have inflorescences composed of two types of flowers: decorative flowers with showy sepals and plain nondecorative flowers. In wild plants of Hydrangea 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.