Molecular Identification and Expression Analysis of GhCYP51G1 Gene, a Homologue of Obtusifoliol-14Alpha-Demethylase Gene, from Upland Cotton

Abstract

For understanding the effects of phytosterols on the development of cotton ( Gossypium hirsutum L.) fibers and the molecular basic of sterol signaling in cotton fiber growth, a gene encoding a homologue of obtusifoliol 14α-demethylase from developing fibers of upland cotton cultivar Xuzhou 142 was cloned through screening cotton fiber express sequence tag (EST) database and contigging the candidate ESTs. The full length of GhCYP51G1 (GenBank accession number EU727154) was 1710 bp, including a 160 bp 5′-untranslated region (UTR), a 1461 bp open reading frame (ORF), and an 89 bp 3′-UTR. The GhCYP51G1 encoded a polypeptide of 486 amino acid residues with a predicted molecular mass of 55.2 kD. The deduced amino acid sequences had high homology with the members of CYP51 family in plant kingdom. Moreover, many typical conserved regions were characterized as the obtusifoliol 14α-demethylase, such as substrate recognition sites and heme-binding region presented in the deduced protein. Quantitative real-time reverse transcript PCR analysis revealed that the higher expression levels of GhCYP51G1 gene were detected in fibers that were 8, 12, and 18 d post anthesis (DPA), and the 12-DPA ovules. These results indicate that GhCYP51G1 gene plays an important role in fiber elongation. Furthermore, auxin significantly down regulates the expression level of GhCYP51G1 in cotton fiber growth, suggesting that phytosterols play a role in the interaction of plant hormones, especially in the interaction of brassinosteroids and auxin.