Identification of CDF family members in apple and their expression in response to sucrose during floral induction

Plant-specific CDF genes encode a class of transcription factors which play crucial roles in plant flowering, especially in photoperiod-regulated flowering. But little is known about the potential functions of <i>MdCDF</i>s during flower induction in apple. In this study, 11 putative <i>MdCDF</i>s were identified and named systematically. Bioinformatic analysis revealed a functional and structural similarity among the <i>MdCDF</i>s. Analysis of tandem and synteny revealed several paired <i>CDF</i> homologs between apple and <i>Arabidopsis</i>. RT-qPCR revealed that <i>MdCDF</i>s exhibited distinct expression patterns in different apple tissues and most of them displayed high expression levels in flowers and leaves. Further expression profiles of <i>MdCDF</i>s were investigated in different-flowering varieties of apple and in response to sugar treatment. The results indicated that <i>MdCDF</i>s were responsive to floral induction. Meanwhile, the expressions of all <i>MdCDF</i>s were inhibited in buds during different floral induction stages after sugar treatment. The expressions of flowering-related and photoperiod pathway-related genes showed differences and may indicate that most of the <i>MdCDF</i>s may function as a light response flowering inhibitor and could be repressed by the sugar-mediated floral induction. Collectively, the comprehensive analysis of <i>MdCDF</i>s provides valuable information on their expression during floral induction that will serve as a foundation for further studies.