Expression of a lipid transfer protein gene family during cotton fibre development

There are six to eight lipid transfer protein-related genes in the allotetraploid Gossypium hirsutum genome, three of which, FSltp1, FSltp2 and FSltp3, were isolated in two genomic clones. All three genes potentially encode full-length lipid transfer proteins (LTPs), but sequence differences between these and the cotton fibre-specific cDNA previously reported, pFS6, suggest that none is likely to encode the fibre transcripts. Gene-specific RT-PCR experiments showed that expression patterns of the three new LTP genes are similar to each other, with transcripts present in all aerial cotton tissues tested, and only pFS6 transcripts are present in fibre cells at elevated levels. PCR analysis of cotton genomic DNA suggested that FSltp1 and FSltp3 are alloalleles, with FSltp3 being derived from the ancestral A genome, and FSltp1 from the D genome. The fibre-specific gene, yet to be isolated, and FSltp2 are also derived from the ancestral D genome of G. hirsutum.