The mediated vector pLB38 was constructed by insertion the 800 bp fragment of CaMV35S promoter from the plasmid pBI 121 into the BamH I site between the CaMV 35S pro- moter and GUS gene of the pBI121 and screening the recombinants containing the directed dupli- cate of CaMV35S promoter with Xba I digest.The plasmid pBI121 and pLB38 were introduced into the Agrobacterium tumefaciens containing Ti plasmid pGV 3850 by triparental-mating tech- nique with the aid of helper plasmid pGJ23. The foreign genes in pLB38 and pBI121 were transferred into the tobcco plants using the leaf -disk co-cultivated method and two kinds transgenic plants were obtained. DNA / DNA dot blot and Southern blot with α-32P labelled probe containing 3kb fragment of CaMV 35S-GUS comfirmed that foreign genes were transferred and integrated into the trans- genic tobacco plant genome

The identification of the product of NPT II gene with NPT II dot as- say

GUS gene with GUS fluorescent assay proved that the foreign NPT II and GUS gene were expressed in transgenic plants.And the GUS activity in pLB38-transformed plants in which the GUS gene was controlled by two directed CaMV35S promoters was three-to four-fold higher than that in the pBI121-transformed plants in which the GUS gene is controlled by single CaMV35S promoter.These results suggested that the promoter number has effect on the expres- sion level of genes controlledy by these promoters.