Isolation and characterisation of the carnation floral-specific MADS box gene, CMB2

The cDNA clone KD81, was isolated from a carnation petal cDNA library based on its strong differential expression in petals compared with leaves. The deduced amino acid sequence of KD81 indicated high homology with members of the MADS box family of transcription factors. Identified within the deduce d amino acid sequence are two conserved domains: an N-terminal, MADS box an d a central. K box. The gene encoding KD81 was termed Carnation MADS Box ge ne 2 (CMB2). Expression of CMB2 is floral-specific and in petal, transcript s were persistent from the initial stages of development through flower ope ning. Transcripts were not detected in vegetative tissues. The CMB2 protein is most homologous to TDR6 from tomato,the product of the petal and stamen identity gene DEFICIENS (DEFA), and several DEFA homologues including SLM3 , STDEF, PMADS1 and APETALA3. Southern blot analysis indicated that CMB2 is present as a single copy within the carnation genome. Characterisation of a genomic clone encoding CMB5 revealed the molecular structure of CMB2 to b e consistent with that reported for other plant MADS box genes. Analysis of the CMB2 promoter sequence revealed the presence of two putative cis-actin g elements known as serum response elements (SREs). These elements are prop osed as the target for MADS box domain binding and may be involved in the r egulation/autoregulation of gene expression. CMB2 represents the first repo rted isolation of a MADS box gene from carnation. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.