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Monotreme lactation protein Is highly expressed in monotreme milk and provides antimicrobial protection

Citation

Enjapoori, AK and Grant, TR and Nicol, SC and Lefevre, CM and Nicholas, KR and Sharp, JA, Monotreme lactation protein Is highly expressed in monotreme milk and provides antimicrobial protection, Genome Biology and Evolution, 6, (10) pp. 2754-2773. ISSN 1759-6653 (2014) [Refereed Article]


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 Copyright The Author(s) 2014

DOI: doi:10.1093/gbe/evu209

Abstract

Monotremes (platypus and echidna) are the descendants of the oldest ancestor of all extant mammals distinguished from other mammals by mode of reproduction. Monotremes lay eggs following a short gestation period and after an even briefer incubation period, altricial hatchlings are nourished over a long lactation period with milk secreted by nipple-less mammary patches located on the female’s abdomen. Milk is the sole source of nutrition and immune protection for the developing young until weaning. Using transcriptome and mass spectrometry analysis of milk cells and milk proteins, respectively, a novel Monotreme Lactation Protein (MLP) was identified as a major secreted protein in milk. We show that platypus and short-beaked echidna MLP genes show significant homology and are unique to monotremes. The MLP transcript was shown to be expressed in a variety of tissues; however, highest expression was observed in milk cells and was expressed constitutively from early to late lactation. Analysis of recombinant MLP showed that it is an N-linked glycosylated protein and biophysical studies predicted that MLP is an amphipathic, α-helical protein, a typical feature of antimicrobial proteins. Functional analysis revealed MLP antibacterial activity against both opportunistic pathogenic Staphylococcus aureus and commensal Enterococcus faecalis bacteria but showed no effect on Escherichia coli, Pseudomonas aeruginosa, Staphylococcus epidermidis, and Salmonella enterica. Our data suggest that MLP is an evolutionarily ancient component of milk-mediated innate immunity absent in other mammals. We propose that MLP evolved specifically in the monotreme lineage supporting the evolution of lactation in these species to provide bacterial protection, at a time when mammals lacked nipples.

Item Details

Item Type:Refereed Article
Keywords:monotreme, echidna, platypus, milk, evolution, antibiotic
Research Division:Biological Sciences
Research Group:Physiology
Research Field:Comparative Physiology
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Environmental Sciences
Author:Nicol, SC (Associate Professor Stewart Nicol)
ID Code:98200
Year Published:2014
Web of Science® Times Cited:8
Deposited By:Zoology
Deposited On:2015-02-04
Last Modified:2017-10-31
Downloads:233 View Download Statistics

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