Tick innate immunity involves humoral and cellular responses. Among the humoral effector molecules in ticks are the defensins which are a family of small peptides with a conserved γ-core motif that is crucial for their antimicrobial activity. Defensin families have been identified in several hard and soft tick species. However, little is known about the presence and antimicrobial activity of defensins from the Australian paralysis tick Ixodes holocyclus. In this study the I. holocyclus transcriptome was searched for the presence of defensins. Unique and non-redundant defensin sequences were identified and designated as holosins 1 - 5. The antimicrobial activity of holosins 2 and 3 and of the predicted γ-cores of holosins 1-4 (HoloTickCores 1-4), was assessed using Gram-negative and Gram-positive bacteria as well as the fungus Fusarium graminearum and the yeast Candida albicans. All holosins had molecular features that are conserved in other tick defensins. Furthermore holosins 2 and 3 were very active against the Gram-positive bacteria Staphylococcus aureus and Listeria grayi. Holosins 2 and 3 were also active against F. graminearum and C. albicans and 5 μM of peptide abrogate the growth of these microorganisms. The activity of the synthetic γ-cores was lower than that of the mature defensins apart from HoloTickCore 2 which had activity comparable to mature holosin 2 against the Gram-negative bacterium Escherichia coli. This study reveals the presence of a multigene defensin family in I. holocyclus with wide antimicrobial activity.

Centre for Comparative Genomics Murdoch University Perth WA 6150 Australia

Department of Biochemistry and Genetics La Trobe Institute for Molecular science La Trobe University Melbourne Victoria 3086 Australia

Faculty of Science University of South Bohemia 37005 České Budějovice Czech Republic; Institute of Parasitology Biology Center Czech Academy of Sciences 37005 České Budějovice Czech Republic; Department of Virology Veterinary Research Institute Brno Czech Republic

INRA UR1264 MycSA 71 Avenue Edouard Bourlaux 33882 Villenave d'Ornon cedex France

Institute for Insect Biotechnology Justus Liebig University of Giessen Heinrich Buff Ring 26 32 35392 Giessen Germany; LOEWE Centre for Translational Biodiversity Genomics Senckenberganlage 25 60325 Frankfurt Germany

Institute for Insect Biotechnology Justus Liebig University of Giessen Heinrich Buff Ring 26 32 35392 Giessen Germany; LOEWE Centre for Translational Biodiversity Genomics Senckenberganlage 25 60325 Frankfurt Germany; Fraunhofer Institute for Molecular Biology and Applied Ecology Department of Bioresources Winchester Strasse 2 35394 Giessen Germany

LOEWE Centre for Translational Biodiversity Genomics Senckenberganlage 25 60325 Frankfurt Germany

Queensland Alliance for Agriculture and Food Innovation The University of Queensland St Lucia Queensland 4072 Australia

SaBio Instituto de Investigación de Recursos Cinegéticos IREC CSIC UCLM JCCM Ciudad Real Spain

UMR BIPAR INRA ANSES Ecole Nationale Vétérinaire d'Alfort Université Paris Est Maisons Alfort 94700 France

Citace poskytuje Crossref.org

The immune factors involved in the rapid clearance of bacteria from the midgut of the tick Ixodes ricinus

Tick defensin γ-core reduces Fusarium graminearum growth and abrogates mycotoxins production with high efficiency