The SEP homologous gene TEMARY regulates inflorescence phenotypes in Hydrangea Macrophylla

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.

Acknowledgments

We thank H. Fukuda, K. Honma, M. Ichige, M. Ishiyama, H. Meguro, Y. Takekawa, and D. Uetake (Nihon University, Fujisawa, Kanagawa, Japan); S. Ogata, H. Kotera, S. Iwata, N. Sera, and N. Tanigawa (University of Shiga Prefecture, Hikone, Shiga, Japan); and Y. Kishida, C. Minami, K. Ozawa, H. Tsuroka, and A. Watanabe (Kazusa DNA Research Institute, Kisarazu, Chiba, Japan) for technical assistance. This study was partially supported by the Japan Society for the Promotion of Science and Grants-in-Aid for Scientific Research, KAKENHI (grant numbers: JP18K14461, JP18K05628, 22H05172, 22H05181, and 24580049).

Author Contributions

K.N. and T.U. performed most experiments and wrote the manuscript. K.S., A.S., T.T., and T.O. assisted with experiments. S.I., M.A., M.A., Y.N., M.K., K.N., T.K., and T.S. participated in the discussions.

Data availability

Sequence reads were deposited in the Sequence Read Archive database of the DNA Data Bank of Japan (DDBJ) under accession numbers DRR510893 (transcriptome reads for a mixture of Blue Sky and BM-1) and DRR510894-DRR510900 (genome reads for the seven lines). TEMARY alleles 1 to 8 sequences were registered under the accession numbers LC795557 to LC795564 in DDBJ. Transcriptome reads for ‘Niijima-1’, ‘Blue Sky’, ‘Jogasaki’, ‘Sumidanohanabi’, and ‘Honajisai’ have been reported in Nashima et al. [13], under the accession number DRA010300.

Conflict of interest statement

The authors declare that they have no competing interests.

Supplementary data

Supplementary data is available at Horticulture Research online.

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