title: Positive Darwinian selection on crustacean hyperglycemic hormone (CHH) of the green shore crab, Carcinus maenas.
abstract: The tissue-specific expression and differential function of the crustacean hyperglycemic hormone (CHH) in Carcinus maenas indicate an interesting evolutionary history. Previous studies have shown that CHH from the sinus gland X-organ (XO-type) has hyperglycemic activity, whereas the CHH from the pericardial organ (PO-type) neither shows hyperglycemic activity nor it inhibits Y-organ ecdysteroid synthesis. Here we examined the types of selective pressures operating on the variants of CHH in Carcinus maenas. Maximum likelihood-based codon substitution analyses revealed that the variants of this neuropeptide in C. maenas have been subjected to positive Darwinian selection indicating adaptive evolution and functional divergence among the CHH variants leading to two unique groups (PO and XO-type). Although the average ratio of nonsynonymous to synonymous substitution (omega) for the entire coding region is 0.5096, few codon sites showed significantly higher omega (10.95). Comparison of models that incorporate positive selection (omega > 1) with models not incorporating positive selection (omega <1) at certain codon sites failed to reject (p=0) evidence of positive Darwinian selection.
authors.affiliation: Department of Biological Science, University of Tulsa, Tulsa, OK 74104, USA. abinash-padhi@utulsa.edu
authors.forename: Abinash
authors.initials: A
authors.lastname: Padhi
authors.forename: Bindhu
authors.initials: B
authors.lastname: Verghese
authors.forename: Subhendu K
authors.initials: SK
authors.lastname: Otta
authors.forename: Binu
authors.initials: B
authors.lastname: Varghese
authors.forename: Karri
authors.initials: K
authors.lastname: Ramu
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D060829:Arthropod Proteins; D003386:Brachyura / Q000235:genetics; D003062:Codon; D019295:Computational Biology; D019143:Evolution, Molecular; D007447:Invertebrate Hormones / Q000235:genetics*; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics*; D012641:Selection, Genetic
chemical_list: D060829:Arthropod Proteins; D003062:Codon; D007447:Invertebrate Hormones; D009419:Nerve Tissue Proteins; C015947:hyperglycemic hormone, crustacean; C012445:molt-inhibiting hormone