Analysis of MIKC c -type MADS-box genes and proteins in the fern Ceratopteris richardii

Abstract

The MIKCc subfamily of MADS-box proteins play a key role in flowering plant reproduction, specifying and patterning the floral organs. MIKCC genes have been identified in non-flowering plants, the number increasing with the amount of whole-genome sequencing information available, but MIKCc functions outside flowering plants are less well understood. In this study, we have cloned and sequenced 14 of the 21 MIKCc genes in the model fern Ceratopteris richardii and identified expressed cDNAs/transcripts for a further 6 genes, extending and correcting previous genome-and transcriptome analysis. We have identified that the majority of Ceratopteris MIKCc genes are expressed in the reproductive sporophyte, with some genes showing reproductive specificity. Using protein alignments and structural modelling, we have shown that Ceratopteris MIKCC proteins are structurally diverse, with over half the proteins possessing extended regions N-terminal to the MADS DNA binding domain, suggesting divergent functions or regulation.