Differential expression patterns of MIKCC-type MADS-box genes in the endangered fern Vandenboschia speciosa

We report and discuss the results of a quantitative reverse transcription polymerase chain reaction (qRT-PCR) analysis of the expression patterns of six MADS-box genes (VsMB2 to VsMB7 genes) identified after Next Generation Sequencing (NGS) and assembly of two transcriptomes, those of the sporophyte and the gametophyte, of the endangered fern species Vandenboschia speciosa. Deduced VsMB amino acid sequences had a typical MIKCC-type structure consisting of a MADS domain, a short I region, a K domain, and a C-terminal region. Sequence and phylogenetic analyses supported the placement of the six analyzed proteins in the three main fern MIKCC protein subfamilies. The expression analyses of the six VsMB genes by qRT-PCR indicate that MIKCC-type genes have a broad expression in the sporophyte and that most of the VsMB genes appear to have also a broad expression in the gametophyte, an ancestral condition. However, two of the genes, VsMB2 and VsMB4, have a residual expression in the gametophyte. Furthermore, VsMB3 and VsMB7 genes are down-regulated in the reproductive structures. This study represents a comprehensive identification and characterization of MADS-box genes in V. speciosa and it supports specialized roles of some of these genes during the two phases of fern development.