Plant Genome III Conference

CLONING AND CHARACTERIZATION OF COTTON FIBER SPECIFIC CDNA ENCODING LIPID TRANSFER PROTEIN.

Cotton (Gossypium hirsutum) fiber is a differentiated epidermal single cell from a developing seed. The development of the fiber can be divided into four phases: initiation, elongation (primary cell wall synthesis), secondary cell wall synthesis, and maturation. of the many genes involved in the control of fiber synthesis, only a few have been isolated and characterized. We have used a PCR-based method to construct a cotton fiber cDNA library in lambda gt10 and subsequently isolated twenty-six fiber-specific cDNA clones using a differential screening method. The nucleotide and derived amino acid sequence data of one cDNA clone (GH3) suggest that it encodes a lipid transfer protein (LTP) of 120 amino acids. The fiber LTP has all structural features of plant nonspecific LTPs including the low molecular weight, a high isoelectric point, low numbers of aromatic amino acids, high contents of proline, glycine, alanine and serine, seven-eight conserved cysteine residues. The presence of a transmembrane signal peptide at the N-terminal would suggest its possible outer cellular location in fiber cells. Northern analysis indicates that the GH3 gene is developmentally regulated.