Positive Darwinian Selection on Crustacean Hyperglycemic Hormone (CHH) of the Green Shore Crab, Carcinus maenas

• Published in: In silico biology 2007, Vol.7 (4-5), p.355-367
• Main Authors: Padhi, Abinash, Verghese, Bindhu, Otta, Subhendu K., Varghese, Binu, Ramu, Karri
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Amino Acid Substitution; Animals; Arthropod Proteins; Biological and medical sciences; Brachyura - genetics; Carcinus maenas; Codon; Computational Biology; Decapoda; Evolution, Molecular; Fundamental and applied biological sciences. Psychology; Genetics of eukaryotes. Biological and molecular evolution; Invertebrata; Invertebrate Hormones - genetics; Molecular Sequence Data; Nerve Tissue Proteins - genetics; Population genetics, reproduction patterns; Selection, Genetic
• ISSN: 1386-6338; 1434-3207
• DOI: 10.3233/ISI-2007-00294

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 (ω) for the entire coding region is 0.5096, few codon sites showed significantly higher ω (10.95). Comparison of models that incorporate positive selection (ω > 1) with models not incorporating positive selection (ω