Temperature adaptation in Dictyostelium: role of Delta5 fatty acid desaturase.
Membrane fluidity is critical for proper membrane function and is regulated in part by the proportion of unsaturated fatty acids present in membrane lipids. The proportion of these lipids in turn varies with temperature and may contribute to temperature adaptation in poikilothermic organisms. The fundamental question posed in this study was whether the unsaturation of fatty acids contributes to the ability to adapt to temperature stress in Dictyostelium. First, fatty acid composition was analysed and it was observed that the relative proportions of dienoic acids changed with temperature. To investigate the role of dienoic fatty acids in temperature adaptation, null mutants were created in the two known Delta5 fatty acid desaturases (FadA and FadB) that are responsible for the production of dienoic fatty acids. The fadB null mutant showed no significant alteration in fatty acid composition or in phenotype. However, the disruption of fadA resulted in a large drop in dienoic fatty acid content from 51.2 to 4.1 % and a possibly compensatory increase in monoenoic fatty acids (40.9-92.4 %). No difference was detected in temperature adaptation with that of wild-type cells during the growth phase. However, surprisingly, mutant cells developed more efficiently than the wild-type at elevated temperatures. These results show that the fatty acid composition of Dictyostelium changes with temperature and suggest that the regulation of dienoic fatty acid synthesis is involved in the development of Dictyostelium at elevated temperatures, but not during the growth phase.
Saito
Tamao
T
Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo, 060-0810 Japan.
Kato
Atsushi
A
Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo, 060-0810 Japan.
Ochiai
Hiroshi
H
Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo, 060-0810 Japan.
Morita
Naoki
N
Research Institute of Genome-based Biofactory, National Institute of Advanced Industrial Science and Technology (AIST), Toyohira-ku, Sapporo 062-8517 Japan.
D000222:Adaptation, Physiological; D000818:Animals; D003470:Culture Media; D004023:Dictyostelium / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development*; D044943:Fatty Acid Desaturases / Q000378:metabolism*; D005227:Fatty Acids / Q000032:analysis; D018507:Gene Expression Regulation, Developmental; D018869:Heat-Shock Response; D009154:Mutation; D013696:Temperature
D003470:Culture Media; D005227:Fatty Acids; D044943:Fatty Acid Desaturases