The SEPALLATA-like gene HrSEP1 in Hippophae rhamnoides regulates flower development by interacting with other MADS-box subfamily genes

MADS-box genes are classified into five categories: ABCDE, including <i>SEP1</i>, <i>SEP2</i>, <i>SEP3</i>, <i>SEP4</i>, and other homologous genes, which play important roles in floral organ development. In this study, the cDNA sequence of the <i>HrSEP1</i> gene was cloned by RT-PCR and confirmed that this gene belongs to the MADS-box gene family. In addition, subcellular localization experiments showed that the <i>HrSEP1</i> protein was localized in the nucleus. We verified the interaction of <i>HrSEP1</i> with <i>HrSOC1</i>, <i>HrSVP</i>, and HrAP1 using yeast two-hybrid and bimolecular fluorescence complementation assays. These genes jointly regulate the growth and development of floral organs. We also found a strong synergy between <i>HrSEP1</i> and <i>AP1</i> genes in sepals, petals, and stamens by transgenic methods and fluorescence quantitative PCR, suggesting that <i>HrSEP1</i> and <i>AP1</i> may co-regulate the development of these structures. In conclusion, the expression of <i>HrSEP1</i> has a certain effect on the development of floral organs, and these findings lay the foundation for further research on the biological functions of MADS transcription factors in <i>Hippophae rhamnoides</i>.