Isolation of three homologous AP1-like MADS-box genes in crocus (Crocus sativus L.) and characterization of their expression

We have cloned and characterized the expression of three homologous Apetala1-like (AP1-like) genes from a crocus variety (Crocus sativus L) cultivated exclusively in Kozani, at northern Greece. The three different homologous genes were designated CsAP1 (C. sativus APETALA1) and each one was named CsAP1a, CsAP1b, and CsAP1c. They are the first reported MADS-box genes isolated from this important monocot species cultivated for its flowers.The deduced amino acid sequence of the three genes indicated high homology with members of the MADS-box family of transcription factors, and particularly with other members of the AP1-like family of MADS-box proteins that control floral-meristem and floral-organ identity. All the isolated sequences lack the typical CaaX-motif that is present in dicot AP1 functional proteins but absent in the monocot homologues thus far examined. CsAP1a and CsAP1b are more similar having 88.2% identical amino acids while CsAP1c is more divergent having 70.9% similarity with CsAP1a, and 64.5% similarity with CsAP1b. Phylogenetic analysis of the isolated genes at the amino acid level indicated that they form a clade with other monocot AP1-like genes from maize (ZmM28), barley (BM3), and rice (OsMADS18). Southern experiments indicated the presence of additional AP1-like homologues in crocus.Expression analysis indicated the presence of different amount of steady-state mRNAs for all the three homologous genes in leaves, as well as, in the three mature flower parts, namely: tepals, stamen and carpels. Similar expression pattern display many monocot AP1-like MADS-box genes, which comprise a distinct phylogenetic clade of monocot class A MADS-box genes and may reflect a novel, yet unidentified role of their corresponding proteins in these species. [Copyright &y& Elsevier]