Abstract：Brown cotton processes the natural brown fiber color, without dyeing during spinning and processing process, which is really the "ecological", "environmental protection" cotton. Molecular cloning and understanding of the brown pigment synthesis-related gene in cotton fiber is very important to reveal molecular mechanism in the formation and accumulation of brown pigment. The brown fiber Asian cotton (Gossypium arboreum) Cixizimian and white fiber Yuyaozhongmian were selected in this study. Cotton fiber total RNA was extracted from the cotton fiber different development period. Ultimately, only one expressed fragment of 500 bp was obtained from the cDNA of brown cotton fiber. With sequencing and bioinformatics analysis, one gene named GaTT12a (GenBank accession number: JX013908) was cloned using the RT-PCR method. The sequence of the gene showed 75% homologous with testa brown pigment synthesis TT12 gene of Arabidopsis thaliana in amino acid sequence. The gene encoded 490 amino acid residues with the molecular weight of 52.7 kD, belonging to MATE super-gene family. Real-time quantitative PCR analysis of the gene showed that the gene presented super-dominant expression both in the brown cotton fiber, testa of brown and white cotton, while which not detected in white fiber. The result indicated that The GaTT12a gene was involved in the formation of brown pigment in cotton fiber, the result further suggested that there was the same synthesis metabolic pathway of the brown pigment in both testa and fiber. The above result gives the fundamental information for further understanding its function participating in the formation of brown pigment of cotton, the relationship of brown pigment of cotton fiber and brown pigment of seed coat.
