Cloning And Sequence Analysis Of Two Putative α-Galactosidase Genes Of Cucumber (Cucumis Sativus L.)

a-galactosidase is an important hydrolase which exist widely in higher plants and animals and microorganism. Our laboratory has obtained4full length cDNA sequences of a-galactosidases in cucumber, according to homological sequences of a-galactosidase genes in other plants. Through published cucumber genome sequence and the homology analysis, other two alpha-galactosidases also exist in cucumber.In this study,2full length cDNA sequences of a-galactosidases were obtained by RT-PCR(Reverse Transcription-Polymerase Chain Reaction) and RACE(Rapid amplification of cDNA ends) in cucumber. They are named:cucumber acid a-galactosidases Ⅲ(JN680267), cucumber alkaline a-galactosidasesⅢ(JQ327828). Cucumber acid a-galactosidasesⅢ consisted of430amino acid residues with amolecular weight of47.9KD. Cucumber alkaline a-galactosidasesⅢ consisted of783amino acid residues with amolecular weight of86.1KD. The deduced protein sequence according to the cDNA sequence analysis showed that the acid a-galactosidase glucosidaseⅢ protein C-terminal existence of a signal peptide, located in the vacuoles, alkaline alpha-galactosidaseⅢ are located in the cytoplasmin.Collected α-galactosidase sequence of higher plants, cluster analysis showed that the acid α-galactosidases can be divided into three groups, three kinds of acid a-galactosidases of cucumber belong to one of them; alkaline α-galactosidase glycosidases can be divided into three groups, each group contains one kind of alkaline a-galactosidase of cucumber. The possible function of the six α-galactosidases:The group of acid α-galactosidases1related with fruit ripening and leaf development; the group of acid a-galactosidases2has function of cell wall and seed development and related with cold resistance; the group of acid a-galactosidases3has function of leaf senescence; the group of alkaline a-galactosidases1has function of fruit and seed development and leaf senescence; the group of alkaline a-galactosidases2hydrolyzes stachyose with seed development and related with drought press; the group of alkaline a-galactosidases3has function of fruit and seed development and leaf senescence and stress. These analyzes provide clues of study the physiological functions of the cucumber variety of α-galactosidase glycosidase in our laboratory.