Cloning, Expression And Transformation Of Silicon Transport Gene CSiT-1and CSiT-2in Cucumber

Cucumber(Cucumis sativus L.)，one of the most important horticultural plants whichis widely cultivated in the world and accounts for a pivotal position of vegetableproduction and consumption in China.A number of studies on physiological mechanisms responsible for silicon uptake,transport and accumulation in dicotyledonous plants have been done, while its molecularregulation mechanism needs more deep research. In this study, we take Zhongnong8cucumber as the material and two silicon transport genes from cucumber were isolated andcharacterized by using homological clone, which were designed as CSiT-1and CSiT-2respectively, then these two eukaryotic expression vectors were constructed. In addition, theeffect of salt stress on expression level of CSiT-1and CSiT-2genes was explored by usingdifferent exogenous silicon(Na2SiO3·9H2O) treatments. The main results were achieved asfollows:(1) Two full-length cDNAs encoding CSiT-1and CSiT-2of Cucumber were clonedrespectively. The full length of CSiT-1contains876bp nucleotides comprising377aminoacid. The clone of CSiT-2contains786bp nucleotides comprising262amino acid. Thesetwo sequences have been submitted to the GenBank databases with accession numberFJ595947and FJ595948respectively.(2)According to the homologous sequences analysis, the putative amino acidsequence of these two genes showed high similarities with silicon transport genes of otherplants which indicated that these two full length cDNAs encoded CSiT-1and CSiT-2respectively.(3)Two full-length cDNAs were subcloned into the expression vector pBI-121downstream of the35S-CaMV promoter to form sense constructs respectively. Then theconstructs were introduced into Agrobacterium tumefaciens LBA4404by the freezingtransformation method and verified by PCR. The transgenic cucumber plants have been obtainedand the T1transgenic plants are still in screening and analysis.(4)CSiT-1and CSiT-2had significant expression differences in leaves of wild typeCucumber under low silicon treatment (0.02mM) and high silicon treatment (1.7mM).