Characterization of B- and C-class MADS-box genes in medicinal plant <i>Epimedium sagittatum</i>

Abstract

The basal eudicot Epimedium (Barrenwort) exhibits innovative floral morphology in the form of petal spurs filled with nectar and petaloid sepals. The B-class MADS-box genes <italic>APETALAS3</italic> (<italic>AP3</italic>) and <italic>PISTILLA</italic> (<italic>PI</italic>) determine sepal and petal identity while the C-class gene <italic>AGAMOUS</italic> (<italic>AG</italic>) determines carpel and stamen identity in <italic>Arabidopsis</italic>. Complex histories of gene duplication resulted in subsequent subfunctionalization or neofunctionalization of paralogs. Here, a total of four B- and two C-class genes were successfully isolated from <italic>E. sagittatum</italic>. Phylogenetic analysis showed that <italic>EsAP3-1</italic>, <italic>EsAP3-2</italic>, and <italic>EsAP3-3</italic> are part of the AP3 clade; <italic>EsPI</italic> is part of the PI group; and <italic>EsAG</italic> and <italic>EsAG11</italic> clustered into the AG and AG11 groups, respectively. Quantitative real-time PCR was utilized to detect the expression patterns of these genes, and all B-class genes except for <italic>EsAP3-3</italic> were found to be universally expressed. The transcribed <italic>EsAG</italic> and <italic>EsAG11</italic> genes were confined to reproductive organs. In addition, yeast three and two hybrid assays were used to explore the status of protein complexes. EsAP3-1 was found to have broadly interactive partners, and EsPI can form a heterodimer with EsAP3-1 and EsAP3-2. Transgenic EsAG overexpression in wild-type Arabidopsis confirmed the conserved function determining carpel development.