Isolation of Novel Cotton Promotors to drive the Robust Expression of useful Genes in Transgenic Cotton

Date Issued:2005-06-30

Abstract

The performance of the first generation of transgenic (INGARD) plants released in Australia since 1996 was disappointing at a commercial level, despite the considerable reduction in pesticide usage required to grow the crop. This was primarily because of the variable performance of the plants in insect control, either across farms, or at different times of the season. A decline in efficacy had previously been noted at the end of the season, but many cases of serious decline in insect control have been reported much earlier, requiring immediate spraying to control insect outbreaks. This decline in expression appears to be a consequence of the decrease in the activity of the 35S promoter driving the INGARD gene probably in response to either environmental or physiological influences on the plant. These problems cannot be corrected in the short-term using gene technology and we must rely on our breeders to select for individual plants that show more robust expression from the promoter driving INGARD. Monsanto has been able to resolve some of the problems with INGARD in their second generation Bollgard II cotton with higher levels of expression of the Cry2Ab gene. In the longer-term, for new biotech products, we can try to find better promoters that will express throughout the season or that at least are stronger during the period when the INGARD gene starts to decline. New gene constructs could then be developed that will either complement the existing genes or replace them and the same promoters could be used in conjunction with a number of other genes in the biotechnology pipeline. Using new genomic technologies we have identified a couple of possible promoters that might show the desired pattern of expression throughout the season, but they need to be fully evaluated in transgenic cotton plants. One promoter from a photosynthetic gene has been developed into gene constructs and introduced into both an easily engineered model plant and also into transgenic cotton, so that we can test its performance under field conditions. All the data is not yet to hand, but we hope that this, and other promoters to be analysed later, will give robust field expression in transgenic cotton and add to our toolkit of genes and pieces of genes from which we can develop more robust transgenic products for the cotton industry as well as provide biotechnologists with a greater selection of promoters to produce new biotech products.

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