Identification and characterization of class E genes involved in floral organ development in <i>Dianthus chinensis</i>

Abstract

The<italic> SEPALLATA</italic> (<italic>SEP</italic>) gene, as a 'glue' for the 'floral quartets model', plays an important role in floral organ development by forming tetramers with class A-, B-, and C- genes. The functional differentiation of class E genes has been reported in different species. Carnation (<italic>Dianthus</italic> spp.) is a world-famous economic flower that has been extensively used in landscaping, but the roles of SEP genes in carnation are unclear. Here, we found that the class E genes of <italic>D.</italic> <italic>chinensis</italic> cultivar 'L' showed different expression patterns during floral organ primordium development by transcriptome analysis. Combined with quantitative real-time PCR, its tissue and specific stage expression patterns were also different in different subclades. In addition, a yeast two-hybrid experiment was carried out to explore the interaction patterns of class E genes with other class A-, B-, and C- genes. Only DcSEP3s and DcSEP4s proteins interacted with all three classes of A-, B-, and C- proteins, and interestingly, is that DcSEP3-1 only interacted with the DcAP1 protein of class A, while the DcSEP3-2 protein only interacted with DcFUL1. Transgenic experiments showed that overexpression of <italic>DcSEP3-2</italic> genes in <italic>Arabidopsis</italic> resulted in early flowering, smaller rosettes, dwarfism and abnormal floral organs. The transgenic line overexpressing of<italic> DcSEP3-1</italic> only showed an early flowering phenotype. All these results indicated that the two <italic>DcSEP3s</italic> of class E genes in <italic>D.</italic> <italic>chinensis</italic> may undergo sub-functionalization. These findings advance our understanding of the molecular mechanisms of flower development in carnation.