Abstract: Genetic and expressional stability of Bt toxin gene is crucial for the breeding of insect-resistant transgenic cotton varieties and their commercialization. The impact of different temperature on the expression of Bt toxin gene in R5 generation plants during their development was studied. The results indicated that the time point of when the expression of Bt toxin protein in transgenic insect-resistant cotton plants became lower during the development was affected because different thermal treatments had great impact on the development of transgenic plants and their Bt toxin gene expression level. Under high temperature treatment, the silencing of Bt toxin gene during the developmental stages happened ahead of time, leading to the level of Bt toxin dropped dramatically. This was probably caused by the gene regulation at post-transcriptional level, and the full-length mRNA of Bt toxin gene decreased thereafter. Therefore, it is very important to take measures earlier in practice in order to avoid the loss caused by cotton boll-worm during the high temperature period.

Key words: Bt transgenic insect-resistant cotton plant, Temperature, Gene expression