Molecular cloning, characterization and expression analysis of MADS-box genes associated with reproductive...

The repertoire and functions of MADS-box family transcription factors (TFs) largely remains unexplored with respect to floral organogenesis of Momordica dioica Roxb. Degenerative PCR followed by rapid amplification of cDNA ends was employed in the present study to clone and characterize 17 MADS-box genes (designated as MdMADS01 to MdMADS17) from the floral buds of M. dioica. The cloned genes were clustered into three subgroups (11 MIKC^C, 4 MIKC* and 2 Mα) based on phylogenetic relationships with the MADS-box genes from Cucumis sativus, Cucumis melo and Arabidopsis thaliana. Southern hybridization showed that all the isolated genes were represented by single copy locus in the M. dioica genome. Gene structure analysis revealed 1-8 exons in MdMADS-box genes with the number of exons in MIKC greatly exceeding from that in M-type genes. Motif elicitation of the MdMADS-box genes indicated the presence of additional domains with MIKC type, suggesting that they had more complex structures. Expression analysis of MdMADS genes in six M. dioica transcriptome suggested that, 11 MIKC^C-type genes are associated with floral homeotic functions, 4 MIKC*-type genes (MdMADS12 to MdMADS15) controlled the growth of male gametophyte, while the two M-type genes (MdMADS16 and MdMADS17) played significant role in female gametogenesis and seed development. Overall, these are the first set of MADS-box genes from M. dioica exhibiting a differential expression pattern during floral development. The results from this study will provide valuable information for further functional studies of candidate MADS-box genes in the sexual dimorphism of this economically important dioecious cucurbit.