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The Selective Cause of an Ancient Adaptation
Author(s) -
Michael Antony
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a210-b
Subject(s) - isocitrate dehydrogenase , idh1 , nad+ kinase , biology , isocitrate lyase , adaptation (eye) , phenotype , gene , genetics , dehydrogenase , phylogenetic tree , enzyme , biochemistry , mutation , glyoxylate cycle , neuroscience
A central goal in evolutionary biology is to understand the origins and mechanisms underlying ancient adaptive events. Guided by phylogenetic analysis, genetic engineering has been used to reconstruct ancestral genes allowing ancient phenotypes to be revealed. However, direct investigation of adaptation requires an examination of the fitness consequences of these reconstructions. We replaced the wildtype gene encoding the NADP‐dependent isocitrate dehydrogenase of Escherichia coli by an engineered one possessing the ancestral NAD‐dependent phenotype. The engineered enzyme is disfavored during competition for acetate and selection intensifies in genetic backgrounds where other sources of reduced NADP have been removed. Further confirmation that wildtype isocitrate dehydrogenase is an important source of reduced NADP during growth on acetate comes from a survey of sequenced prokaryotic genomes. Those encoding isocitrate lyase, which is essential for growth on acetate, always have an NADP‐dependent isocitrate dehydrogenase. Those with only an NAD‐dependent isocitrate dehydrogenase never have isocitrate lyase. Hence, the NADP‐dependence of prokaryotic isocitrate dehydrogenase appears to be an adaptation to growth on acetate. The metabolic basis of an ancient adaptive event is thus revealed.