Abstract: In present study，we analyzed the information of apple tonoplast monosaccharide
transporter（TMT）gene family based on Malus genome database，and explored their expression
characteristics by qRT-PCR and analyzed the relationship between their expression and sugar accumulation
in apple. The results showed that apple had 5 transcribed MdTMT genes with 11 transmembrane domains
and a hydrophilic loop located in the cytoplasm. These MdTMTs are highly homologous with Arabidopsis
thaliana and Vitis vinifera TMTs. Quantitative expression analysis showed that all MdTMTs were expressed
in apple with a higher expression abundance of MdTMT1 and lower expression abundance of MdTMT3 and
MdTMT4. MdTMT1 had the highest expression abundance in flower and fruit while MdTMT2 in fruit.
The expression of MdTMT1 and MdTMT2 had significantly positive correlation with total sugar，
reducing sugar，fructose and sucrose during fruit development，especially MdTMT2. These results
suggested that MdTMT1 and MdTMT2 may participate in the accumulation of fructose and sucrose in the fructescence of apple.

Key words: Malus ×, domestica；tonoplast monosaccharide transporter；expression；sugar；fruit