Characterization of Three SEPALLATA-Like MADS-Box Genes Associated With Floral Development in Paphiopedilum henryanum (Orchidaceae)

Abstract

Paphiopedilum(Orchidaceae) is one of the world’s most popular orchids that is found in tropical and subtropical forests and has an enormous ornamental value.SEPALLATA-like (SEP-like) MADS-box genes are responsible for floral organ specification. In this study, threeSEP-like MADS-box genes,PhSEP1,PhSEP2, andPhSEP3, were identified inPaphiopedilum henryanum. These genes were 732–916 bp, with conserved SEPI and SEPII motifs. Phylogenetic analysis revealed thatPhSEPgenes were evolutionarily closer to the core eudicotSEP3lineage, whereas none of them belonged to core eudicotSEP1/2/4clades.PhSEPgenes displayed non-ubiquitous expression, which was detectable across all floral organs at all developmental stages of the flower buds. Furthermore, subcellular localization experiments revealed the localization of PhSEP proteins in the nucleus. Yeast two-hybrid assays revealed no self-activation of PhSEPs. The protein–protein interactions revealed that PhSEPs possibly interact with B-class DEFICIENS-like and E-class MADS-box proteins. Our study suggests that the threeSEP-like genes may play key roles in flower development inP. henryanum, which will improve our understanding of the roles of theSEP-like MADS-box gene family and provide crucial insights into the mechanisms underlying floral development in orchids.