Ovodefensins, an Oviduct-Specific Antimicrobial Gene Family, Have Evolved in Birds and Reptiles to Protect the Egg by Both Sequence and Intra-Six-Cysteine Sequence Motif Spacing1

• Published in: Biology of reproduction Vol. 92; no. 6
• Main Authors: Whenham, Natasha, Lu, Tian Chee, Maidin, Maisarah B.M, Wilson, Peter W, Bain, Maureen M, Stevenson, M. Lynn, Stevens, Mark P, Bedford, Michael R, Dunn, Ian C
• Format: Journal Article
• Language: English
• Published: Society for the Study of Reproduction, Inc 01.06.2015
• Subjects: antimicrobial; chicken; defensin; egg; Escherichia coli; evolution; oviduct; Staphylococcus aureus; steroid
• ISSN: 0006-3363; 1529-7268
• DOI: 10.1095/biolreprod.114.126839

Ovodefensins are a novel beta defensin-related family of antimicrobial peptides containing conserved glycine and six cysteine residues. Originally thought to be restricted to the albumen-producing region of the avian oviduct, expression was found in chicken, turkey, duck, and zebra finch in large quantities in many parts of the oviduct, but this varied between species and between gene forms in the same species. Using new search strategies, the ovodefensin family now has 35 members, including reptiles, but no representatives outside birds and reptiles have been found. Analysis of their evolution shows that ovodefensins divide into six groups based on the intra-cysteine amino acid spacing, representing a unique mechanism alongside traditional evolution of sequence. The groups have been used to base a nomenclature for the family. Antimicrobial activity for three ovodefensins from chicken and duck was confirmed against Escherichia coliand a pathogenic E. colistrain as well as a Gram-positive organism, Staphylococcus aureus, for the first time. However, activity varied greatly between peptides, with Gallus gallusOvoDA1 being the most potent, suggesting a link with the different structures. Expression of Gallus gallusOvoDA1 (gallin) in the oviduct was increased by estrogen and progesterone and in the reproductive state. Overall, the results support the hypothesis that ovodefensins evolved to protect the egg, but they are not necessarily restricted to the egg white. Therefore, divergent motif structure and sequence present an interesting area of research for antimicrobial peptide design and understanding protection of the cleidoic egg.