Isolation and Characterization of a Stress-Dependent Plastidial Δ¹² Fatty Acid Desaturase from the Antarctic Microalga Chlorella vulgaris NJ-7

• Published in: Lipids 2010, Vol.45 (2), p.179-187
• Main Authors: Lu, Yandu, Chi, Xiaoyuan, Li, Zhaoxin, Yang, Qingli, Li, Fuchao, Liu, Shaofang, Gan, Qinhua, Qin, Song
• Format: Article
• Language: English
• Subjects: acclimation; Antarctic Chlorella; Biomedical and Life Sciences; Chlorella vulgaris; Cold stress; cold tolerance; complementary DNA; fatty acid desaturation; gene expression regulation; Gene regulation; Life Sciences; Lipidology; Medical Biochemistry; Medicinal Chemistry; microalgae; Microbial Genetics and Genomics; molecular cloning; Neurochemistry; Nutrition; Original Article; plastids; Saccharomyces cerevisiae; Salt stress; salt tolerance; sequence analysis; stearoyl-CoA desaturase; Δ12 fatty acid desaturation
• ISSN: 0024-4201; 1558-9307
• DOI: 10.1007/s11745-009-3381-8

An acclimation to the changing physicochemical conditions and high amount of Δ¹²-unsaturated fatty acids of the Antarctic Chlorella vulgaris NJ-7 prompted us to speculate about the involvement of Δ¹²-fatty acid desaturases (FAD) in its adaptation to the extremely unfavorable ambience. A full-length cDNA sequence, designated CvFAD6, was isolated from C. vulgaris NJ-7 via RT-PCR and RACE methods. Sequence alignment showed that the gene was homologous to corresponding Δ¹²-FAD from other eukaryotes. Phylogenetic analysis showed that it was grouped with plastidial Δ¹²-FAD with conserved histidine boxes. Yeast cells transformed with a plasmid construct containing CvFAD6 coding region accumulated a considerable amount of linoleic acid (18:2Δ⁹,¹²), normally not present in wild-type yeast cells, suggesting that the isolated gene encodes a functional Δ¹² enzyme. The correlation between the accumulation of CvFAD6 and temperature has been examined by real time PCR. The analysis showed a constant expression of CvFAD6 from 25 to 15 °C whereas a fourfold increased from 25 to 4 °C. Moreover, CvFAD6 transcription was more sensitive to saline stress since a 20-fold increase at 6% NaCl was detected. Our data demonstrate that CvFAD6 is the enzyme responsible for the Δ¹² fatty acids desaturation involved in low temperature and high salinity acclimation for Antarctic C. vulgaris NJ-7.