Identification and Characterisation of Cotton Boll Wall-Specific Gene Promoters for Future Transgenic Cotton Varieties

Current transgenic cotton varieties constitutively express transgenes encoding anti-pest proteins to protect against plant damage caused by insect attack. However, restricting the spatial expression of transgenes to the tissues in which their products are required is likely to improve crop performance and reduce environmental impacts. Therefore, we sought to identify native gene promoters that would restrict transgene expression to the boll wall of the cotton plant. Six abundant mRNAs that accumulated preferentially in the boll wall were identified, and the gene promoters of two of these mRNAs were identified, isolated and characterised. The promoters of a proline-rich protein gene (GhPRP3) and a chalcone synthase gene (GhCHS1) were demonstrated to drive boll wall-preferential expression of a reporter gene in a transient transformation system. In silico analyses of the GhPRP3 and GhCHS1 promoters identified numerous previously identified cis-acting regulatory elements (CAREs) as well as the presence of three novel shared CAREs. The identification and characterisation of these promoters provides an important step in the development of the next generation of transgenic plants.