Abstract: ObjectiveIn the present experiment,cell wall invertase gene(SoCIN1)of sugarcane was cloned and its expression characteristics in genetically modified tobacco plants were studied to provide reference for function research of gene SoCIN1.MethodCoding region sequence of gene SoCIN1 was cloned. The sense expression vector pBI121-So-CIN1 was constructed by gene recombination technology,and it was transformed into tobacco variety K346 by leaf discs method through Agrobacterium tumefaciens EHA105. SoCIN1 genetically modified tobacco was obtained after resistance screening and PCR amplification. Expression of gene SoCIN1 in leaf,soluble sugar content in leaf,CIN activity and plant height were measured by semi-quantitative PCR(wild tobacco as CK).ResultThe coding region sequence of gene SoCIN1 cloned was 1731 bp,whose nucleotide sequence homology was 100%with that of gene SoCIN1(JQ312298)pub-lished by GenBank. Plant sense expression vector was constructed to transform tobacco. The results of PCR amplification showed that gene SoCIN1 had been integrated into tobacco genome DNA . Transgenic tobacco was screened continuously through F0 and F1 generation,and four SoCIN1 genetically modified tobacco lines(T-1,T-2,T-3 and T-4)were obtained. Expression of gene SoCIN1 could be detected in leaves of four transgenic tobacco lines,among which the highest was found in T-1,followed by T-3 ,and the lowest in T-4. Compared with wild tobacco,soluble sugar content,CIN activity in leaves and plant height of four transgenic lines improved obviously. CIN activities in four transgenic lines were signifi-cantly higher than that of wild type(P<0.05,the same below),and CIN activity of T-1 was higher than those of other three transgenic tobacco lines. Soluble sugar contents in leaves of T-1,T-2 and T-3 were significantly higher than that of wild type tobacco 39.68%,19.95%and 31.15%respectively. Plant height of T-1,T-2,T-3 and T-4 increased by 15.57%, 2.90%,5.74%and 5.22%respectively compared with wild type,but only T-1 was significantly higher than that of wild tobacco.ConclusionOverexpression of gene SoCIN1 in SoCIN1 genetically modified tobacco leaves can raise CIN activity and increase soluble sugar content of tobacco leaves and promote plant growth. It is speculated that the gene SoCIN1 may play a role in sugarcane growth and sucrose accumulation.