Positive selection in glycolysis among Australasian stick insects.
BACKGROUND
The glycolytic pathway is central to cellular energy production. Selection on individual enzymes within glycolysis, particularly phosphoglucose isomerase (Pgi), has been associated with metabolic performance in numerous organisms. Nonetheless, how whole energy-producing pathways evolve to allow organisms to thrive in different environments and adopt new lifestyles remains little explored. The Lanceocercata radiation of Australasian stick insects includes transitions from tropical to temperate climates, lowland to alpine habitats, and winged to wingless forms. This permits a broad investigation to determine which steps within glycolysis and what sites within enzymes are the targets of positive selection. To address these questions we obtained transcript sequences from seven core glycolysis enzymes, including two Pgi paralogues, from 29 Lanceocercata species.


RESULTS
Using maximum likelihood methods a signature of positive selection was inferred in two core glycolysis enzymes. Pgi and Glyceraldehyde 3-phosphate dehydrogenase (Gaphd) genes both encode enzymes linking glycolysis to the pentose phosphate pathway. Positive selection among Pgi paralogues and orthologues predominately targets amino acids with residues exposed to the protein's surface, where changes in physical properties may alter enzyme performance.


CONCLUSIONS
Our results suggest that, for Lancerocercata stick insects, adaptation to new stressful lifestyles requires a balance between maintaining cellular energy production, efficiently exploiting different energy storage pools and compensating for stress-induced oxidative damage.
Landcare Research, Private Bag 92170, Auckland, New Zealand. l.dunning@imperial.ac.uk.
Luke T
LT
Dunning
Alice B
AB
Dennis
Geoffrey
G
Thomson
Brent J
BJ
Sinclair
Richard D
RD
Newcomb
Thomas R
TR
Buckley
D000818:Animals; D003062:Codon; D017753:Ecosystem; D005956:Glucose-6-Phosphate Isomerase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000235:genetics* / Q000378:metabolism; D006019:Glycolysis; D007313:Insecta / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*; D016013:Likelihood Functions; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D012641:Selection, Genetic
D003062:Codon; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D005956:Glucose-6-Phosphate Isomerase