Abstract:

Cotton (Gossypium hirsutum L.) is the most important fiber crop in the plant kingdom. In addition to their economic importance, cotton fibers are an ideal experimental material to study cell differentiation, cell elongation, cell wall biosynthesis. ADP-ribosylation factors (ARFs), a subfamily of the small GTP binding proteins superfamily, are believed to participate in vesicular transport and signal transduction events in the cell. The elongation of cotton fiber requires vesicle trafficking to deposit new wall material and increase plasma membrane area, but the function of ARF within the key developmental processes of fiber is still unknown. The positive clone was screened from cotton anther cDNA library using GHA27 as a probe, and its corresponding genome sequence was obtained by PCR. Southern and Northern blotting were employed to determine the gene copy number and gene expression level of GhARF1 in cotton. The cDNA, designated as GhARF1, encoded a polypeptide of 181 amino acid residues with significant homology to the ADP-ribosylation factor (ARF) of mammalian, plant, yeast. Its deduced amino acid sequence showed that the 20.7kDa protein had consensus with GTP-binding domain P(GLDAAGKT), G’(DVGGQ), G(NKQD). The DNA sequence of GhARF1 is 1.5kb in size, including five exons and four introns. Northern blotting showed that GhARF1 transcript was detected mainly in root and corolla rather than in shoot, bud, leaf, cotyledon and ovule, and maximally in fiber. Southern hybridization suggested that GhARF1 is encoded by multi-copies in the genome of Gossypium herbaceum or Gossypium hirsutum. High transcript level of GhARF1 in fiber cells suggests that GhARF1 may play a role in cotton fiber development, especially in fiber cell elongation.

Key words: ADP-ribosylation factor, structural characteristics, GTP-binding protein, cotton