Cloning and functional characterization of auxin receptor TIR1 in Gossypium hirsutum

Transport inhibitor response 1 (TIR1), as an F-box family protein, is a nucleus receptor of auxin in plants. It is essential in the auxin signal transduction pathway and the expression of auxin-responsive genes. As the most important hormone in plants, auxin has a great influence on the ovule and fiber development of cotton (Gossypium hirsutum L.). Studies on the effect of auxin signal transduction pathway on cotton fiber development can fundamentally solve the problem of fiber yield and quality. The cDNA sequence of G. hirsutum TIR1 was obtained through homologous cloning and rapid-amplification of cDNA ends (RACE). The homology between GhTIR1 and that in Arabidopsis thaliana was 64.8%. To study the functions, subcellular localization, and the specific localization of GhTIR1 sequence, we constructed the fusion expression vector of GhTIR1 and its N-terminal or C-terminal deletion mutant genes with GFP. By transiently transforming Arabidopsis protoplasts and stably transforming Nicotiana tabacum BY-2 cell lines, GhTIR1 was localized in the nucleus through the N-terminal 1–197 amino acid sequence. The expression patterns of GhTIR1 in different organs and ovule and cotton fiber cells at different developmental stages showed that GhTIR1 was highly expressed in the initial and elongation stages of cotton fiber development. These results indicate that GhTIR1 plays an important role in the initiation and elongation of cotton fibers, especially the formation of primary fibers of cotton fiber cells.