title: Screening and molecular identification of overproducing γ-linolenic acid fungi and cloning the delta 6-desaturase gene.
abstract: This research aims at isolating and identifying γ-linolenic acid (GLA)-producing fungi in the traditional Chinese salt-fermented soybean food, Douchi, from Yongchuan, People's Republic of China. In this study, Rhizopus oryzae DR3 was identified as a novel fungal species that produces large amounts of GLA. A full-length cDNA, designated as RoD6 D, with high homology to fungal △6 fatty acid desaturase genes was isolated from R. oryzae by using the rapid amplification of cDNA ends method. It had an open reading frame of 1,176 bp encoding a deduced polypeptide of 391 amino acids. Bioinformatics analysis characterized the putative RoD6 D protein as a typical membrane-bound desaturase, including three conserved histidine-rich motifs, a hydropathy profile, and a cytochrome b5 -like domain in the N-terminus. When the coding sequence was expressed in the Saccharomyces cerevisiae strain INVScl, the encoded product of RoD6 D exhibited △6 fatty acid desaturase activity that led to the accumulation of GLA. The results show that Douchi contains a large natural diverse composition, and some strains could be selected as starters for functional fermented foods. This study has also laid a foundation for developing functional Douchi products for further research.
authors.affiliation: Department of Microbiology, Chongqing Medical University, Chongqing, People's Republic of China.
authors.forename: He
authors.initials: H
authors.lastname: Lu
authors.affiliation: Department of Immunology, Chongqing Medical University, Chongqing, People's Republic of China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhu
mesh_terms: D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D005656:Fungal Proteins / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D005800:Genes, Fungal / Q000235:genetics; D050602:Linoleoyl-CoA Desaturase / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D060847:Metabolic Engineering; D008969:Molecular Sequence Data; D010802:Phylogeny; D012233:Rhizopus / Q000201:enzymology / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D017965:gamma-Linolenic Acid / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D017965:gamma-Linolenic Acid; D050602:Linoleoyl-CoA Desaturase
keywords: GLA; cloning; screening; △6 fatty acid desaturase gene