Abstract: Transient expression system was used to analyze the function of α-mannosidase gene during melon fruit ripening. The full-length α-mannosidase gene was cloned into overexpression vector pPZP221，and two interfering sequences against α-mannosidase gene were constructed into RNAi vector pART27 respectively. These vectors were then transformed into Agrobacterium GV3101 and injected into mature green fruits of melon respectively．The majority of the phenotype related to ripening appeared in the fruit pedicle when the bacterial concentration is OD600 = 1.2. Analysis of α-mannosidase activity showed that the enzyme activity in the tissue transformed by overexpression vector was higher than the non-injected tissue，and it was lower in the tissue transformed by RNAi vectors. The expression levels ofthe α-Man gene and six genes related to fruit ripening were analyzed by qRT-PCR. The results showed that the mRNA level of the α-Man gene in the tissue transformed by overexpression vector was elevated by 1.2 times compared with the non-injected tissue，furthermore the steady-state mRNA levels of the six genes related to ripening also significantly increased. The expression levels of the α-Man gene in the tissue transformed by pART-Man1 and pART-Man2 were reduced about 47% and 37% respectively in comparison to the non-injected tissue，and those of the genes related to ripening were decreased. Our results indicated that the α-mannosidase gene may promote fruit ripening in melon.

Key words: melon, α-mannosidase gene, transient expression, RT-qPCR