ABUNDANT MESSENGER-RNAS SPECIFIC TO THE DEVELOPING COTTON FIBER

Five fibre-specific cDNA clones were isolated by differential screenin g of a cDNA library from cotton fibres, a developmentally synchronous population of non-dividing cells. The genes corresponding to these cDN As were expressed preferentially in fibre cells and exhibited differin g patterns of temporal expression during fibre development. One cDNA e ncoded a lipid transfer protein (LTP), and a second encoded a member o f a group of well-characterised proline-rich proteins (PRP) from plant s. The presence of signal peptide-encoding sequences suggests that bot h the LTP and the PRP are targeted to the extracellular matrix of the fibre, and a role is envisaged for each in cell elongation. Sequence a nalysis showed that a third clone was similar to a previously reported fibre-specific sequence of unknown function, whilst the remaining two cDNA clones showed no sequence similarity to previously reported plan t nucleic acids.