Seven MADS-box genes in apple are expressed in different parts of the fruit

To study the role of MADS-box genes in developing apples (Malus xdomestica Borkh.), clones corresponding to seven different genes, MdMADS5 to MdMADS11 , were isolated from a 2-day-old apple cDNA library. Through DNA sequence c omparison, six genes were classified into the APETALA1 (AP1) group and one gene, MdMADS10, into the AGAMOUS (AG) group. Six of the genes, MdMADS5 to M dMADS10 were found to be preferentially expressed in fruit following pollin ation. These genes also showed differential expression patterns in core, co rtex and skin of young fruit. For instance, MdMADS5, which is highly homolo gous to AP1, showed preferential expression in the cortex and skin tissues while MdMADS10, which is highly homologous to AGL11, showed exclusive expre ssion in the core tissues. The gene MdMADS11 showed a similar expression le vel and pattern in flowers, fruit at several early developmental stages, an d for different fruit tissues. The range of expression patterns suggests th at the genes play different roles in apple development.