Expression Character Of Combinations Aggregated With Different Number Of Bt Genes And Introduction Of Mutant In Transgenic Gossypium Hirsutum L.

The genetic engineering has opened up a new field for plant breeding. It is important for transgenic plants that foreign genes can be expressed stably, and that is also what affects its further application. Mostly, when a foreign gene is inserted into the transformant, its expression and stability can be affected by its integration, such as copy numbers and integration sites. Varying results, which the expression level of foreign genes can be influenced by copy numbers positively, negatively or without any correlation, have been reported in different references. The materials, used in the study, were serials of lines of trans-Bt gene cottons aggregated with different copy numbers, their resistance to bollworms was detected by laboratory bioassay, and their transcription expressions was analyzed by semi-quantitative RT-PCR.Laboratory bioassay indicated combinations with 4 copy numbers of Bt gene ail showed efficacy against bollworms at seedling stage, but not so strong as that of their parents. This indicated that there was co-suppression among Bt genes. In the consecutive 5 generations, the mortality rate of the larva in combination (Shanxi94-24+Zhongxin94) decreased.As the results of semi-quantitative RT-PCR with materials on July 20, 2002, light density ratio was different when Bt gene copy numbers changed, in (Zhongxin94+Shanxi94-24) the ratios were 2R>3R>1R, in (Zhongxin94+R19), they were 1R>2R>3R. There were no evident differences between direct cross and reciprocal cross in all combinations. This phenomenon indicated mega gamete and pollen all contained Bt gene and the foreign Bt gene could be transmitted to their offspring. No differences were found in the transmission capability of mega gamete and pollen.Two mutants of Nankang-6 and R20 were found among transgenic cotton populations. The mutants were different with the normal type to some degree in morphology and fertility. The results of PCR and Southern blot indicated that the Bt gene had already been combined into the cotton chromosome. SSR analysis on R20 indicated there were some differences in the PCR products. There was no difference in the combination locus by Southern blot analysis on Nankang-6 mutant type and normal type.