Isolation and characterization of cDNAs that are preferentially expressed in cotton fiber



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Texas Tech University


Cotton (Gossypium hirsutum L.) fibers are elongated epidermal cells of the ovule. In view of the commercial desirability for long fibers, the study of factors involved in controlling the extent of fiber growth is important. Five cDNAs, Gh-1,-2, -3, -4, and -5, that are preferentially expressed in cotton fiber were isolated by various cloning techniques: Gh-1 by the reverse transcriptase-polymerase chain reaction (RT-PCR) method, Gh-2 by the differential display of mRNA technique, Gh-3 by the combination of differential display of mRNA and arbitrarily-primed fingerprinting of RNA techniques, and Gh-4 and -5 by the rapid amplification of DNA ends (RACE) technique. Expression of Gh-1, -2, and -3 was detected throughout the development of ovules, yet it peaked at around 8- to 10-days post-anthesis. Expression of G/7-2and -3 was also highly abundant in petals. Sequence analysis revealed that Gh-1 contains a tandemly repeated insert and shares homology with the previously reported cotton fiber cDNA, pCKE6. Gh-2 had a sequence similar to Zea mays cDNAs which have the conserved Nterminal region of Tat-binding protein, the frans-activator of HIV-1, suggesting a role of Gh-2 as a transcription factor. The deduced amino acid sequence of Gh-3 revealed that it is a rather hydrophilic protein with a potential signal polypeptide at the N-terminus indicating that Gh-3 may be targeted to a certain organelle. The deduced amino acid sequence of Gh-4 showed that it may code for part of vacuolar H*-ATPase subunit. Sequence analysis through the data base indicated that Gh-5 may encode glutathione S-transferase. Further characterization of these cDNAs was discussed.