title: Adaptive functional diversification of lysozyme in insectivorous bats.
abstract: The role of gene duplication in generating new genes and novel functions is well recognized and is exemplified by the digestion-related protein lysozyme. In ruminants, duplicated chicken-type lysozymes facilitate the degradation of symbiotic bacteria in the foregut. Chicken-type lysozyme has also been reported to show chitinase-like activity, yet no study has examined the molecular evolution of lysozymes in species that specialize on eating insects. Insectivorous bats number over 900 species, and lysozyme expression in the mouths of some of these species is associated with the ingestion of insect cuticle, suggesting a chitinase role. Here, we show that chicken-type lysozyme has undergone multiple duplication events in a major family of insect-eating bats (Vespertilionidae) and that new duplicates have undergone molecular adaptation. Examination of duplicates from two insectivorous bats-Pipistrellus abramus and Scotophilus kuhlii-indicated that the new copy was highly expressed in the tongue, whereas the other one was less tissue-specific. Functional assays applied to pipistrelle lysozymes confirmed that, of the two copies, the tongue duplicate was more efficient at breaking down glycol chitin, a chitin derivative. These results suggest that the evolution of lysozymes in vespertilionid bats has likely been driven in part by natural selection for insectivory.
authors.affiliation: Institute of Molecular Ecology and Evolution, East China Normal University, Shanghai, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Institute of Molecular Ecology and Evolution, East China Normal University, Shanghai, China.
authors.forename: Guimei
authors.initials: G
authors.lastname: He
authors.affiliation: Institute of Molecular Ecology and Evolution, East China Normal University, Shanghai, China.
authors.forename: Huihui
authors.initials: H
authors.lastname: Xu
authors.affiliation: Institute of Molecular Ecology and Evolution, East China Normal University, Shanghai, China.
authors.forename: Xiuqun
authors.initials: X
authors.lastname: Han
authors.affiliation: School of Biological Sciences, University of Bristol, Bristol, United Kingdom.
authors.forename: Gareth
authors.initials: G
authors.lastname: Jones
authors.affiliation: School of Biological and Chemical Sciences, Queen Mary University of London, London, United Kingdom s.j.rossiter@qmul.ac.uk syzhang@bio.ecnu.edu.cn.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Rossiter
authors.affiliation: Institute of Molecular Ecology and Evolution, East China Normal University, Shanghai, China s.j.rossiter@qmul.ac.uk syzhang@bio.ecnu.edu.cn.
authors.forename: Shuyi
authors.initials: S
authors.lastname: Zhang
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D002645:Chickens / Q000378:metabolism; D002685:Chiroptera / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D002686:Chitin / Q000031:analogs & derivatives / Q000378:metabolism; D002688:Chitinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D057075:Enzyme Assays; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D019143:Evolution, Molecular; D020440:Gene Duplication; D015870:Gene Expression; D014644:Genetic Variation; D007313:Insecta; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D009113:Muramidase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012641:Selection, Genetic; D014059:Tongue / Q000201:enzymology
chemical_list: D007527:Isoenzymes; D011994:Recombinant Proteins; D002686:Chitin; C031610:glycolchitin; D002688:Chitinases; D009113:Muramidase
keywords: Chiroptera; adaptive evolution; diet; gene duplication; lysozyme