This project aimed to investigate the expression and function of a number of genes that we believed were involved in the production of the secondary chemical gossypol in cotton. One of the key enzymes in cotton terpene synthesis is cadinene synthase that is encoded by several different members of a large gene family. The promoter of one of these genes was chosen for analysis based on it sequence and when linked to a reporter gene and inserted into cotton drove expression of that GUS reporter gene in an embryo-specific pattern. As we were after a promoter that would allow us to silence gossypol production in cotton seeds (ie embryos) but not elsewhere in the plant this now provides us with a useful molecular tool for delivering gene knockout constructs to the cells in the seed that are making gossypol.

In addition we had previously isolated a gene for an enzyme of the P450 hydroxylase class that are involved in many biochemical conversions of secondary defence chemicals, but we needed to demonstrate that it was involved in gossypol production not some other chemical in cotton. Gene silencing or knockout constructs have been developed for this gene and introduced into transgenic cotton. We hope to be able to analyse the chemical composition of the oils in the gossypol glands to see what effects plants that should be deficient in the hydroxylase have had in terms of terpene production. In an alternative strategy we are also expressing this gene in simple bread yeast to see what biochemical conversions it can achieve when fed with different intermediates in gossypol synthesis.

A third approach has been to clone a peroxidase we believe is involved in the last step of gossypol production and see what changes in chemical composition occur when this particular gene is silenced in transgenic cotton plants.

Overall we are trying to characterise some of the key enzymes and genes in gossypol synthesis and develop strategies for eliminating gossypol just from the seeds of transgenic cotton plants in an attempt to increase the nutritive value of cotton seed meal and oil without affecting the normal defensive role of these chemicals against pests and pathogens of cotton. Unfortunately, the project was suddenly terminated midstream by the resignation of the student for personal family reasons.