Molecular cloning and stress-dependent expression of a gene encoding Delta(12)-fatty acid desaturase in the Antarctic microalga Chlorella vulgaris NJ-7.
The psychrotrophic Antarctic alga, Chlorella vulgaris NJ-7, grows under an extreme environment of low temperature and high salinity. In an effort to better understand the correlation between fatty acid metabolism and acclimation to Antarctic environment, we analyzed its fatty acid compositions. An extremely high amount of Delta(12) unsaturated fatty acids was identified which prompted us to speculate about the involvement of Delta(12) fatty acid desaturase in the process of acclimation. A full-length cDNA sequence, designated CvFAD2, was isolated from C. vulgaris NJ-7 via reverse transcription polymerase chain reaction (RT-PCR) and RACE methods. Sequence alignment and phylogenetic analysis showed that the gene was homologous to known microsomal Delta(12)-FADs with the conserved histidine motifs. Heterologous expression in yeast was used to confirm the regioselectivity and the function of CvFAD2. Linoleic acid (18:2), normally not present in wild-type yeast cells, was detected in transformants of CvFAD2. The induction of CvFAD2 at an mRNA level under cold stress and high salinity is detected by real-time PCR. The results showed that both temperature and salinity motivated the upregulation of CvFAD2 expression. The accumulation of CvFAD2 increased 2.2-fold at 15 degrees C and 3.9-fold at 4 degrees C compared to the alga at 25 degrees C. Meanwhile a 1.7- and 8.5-fold increase at 3 and 6% NaCl was detected. These data suggest that CvFAD2 is the enzyme responsible for the Delta(12) fatty acids desaturation involved in the adaption to cold and high salinity for Antarctic C. vugaris NJ-7.
Lu
Yandu
Y
Yantai Institute of Coastal Zone Research for Sustainable Development, Chinese Academy of Sciences, Yantai, People's Republic of China. luyandu@webmail.hzau.edu.cn
Chi
Xiaoyuan
X
Yang
Qingli
Q
Li
Zhaoxin
Z
Liu
Shaofang
S
Gan
Qinhua
Q
Qin
Song
S
D000222:Adaptation, Physiological / Q000235:genetics*; D020418:Algal Proteins / Q000235:genetics* / Q000302:isolation & purification; D000595:Amino Acid Sequence; D000864:Antarctic Regions; D048408:Chlorella vulgaris / Q000201:enzymology / Q000235:genetics*; D003001:Cloning, Molecular; D003080:Cold Temperature; D017124:Conserved Sequence; D018076:DNA, Complementary / Q000235:genetics; D044943:Fatty Acid Desaturases / Q000235:genetics* / Q000302:isolation & purification; D008969:Molecular Sequence Data; D010802:Phylogeny; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D012441:Saccharomyces cerevisiae; D054712:Salinity; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013312:Stress, Physiological / Q000235:genetics
D020418:Algal Proteins; D018076:DNA, Complementary; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D044943:Fatty Acid Desaturases; C040448:delta-12 fatty acid desaturase