title: Fungal infection dynamics in response to temperature in the lepidopteran insect Galleria mellonella.
abstract: This study examines how the dynamics of fungus-insect interactions can be modulated by temperature. The wax moth, Galleria mellonella, is a well-studied and important model insect whose larvae in the wild develop optimally at around 34 °C in beehives. However, surprisingly little research on wax moths has been conducted at relevant temperatures. In this study, the entomopathogenic fungus Metarhizium robertsii inflicted rapid and substantial mortality on wax moth larvae maintained at a constant temperature of 24 °C, but at 34 °C a 10 fold higher dose was required to achieve an equivalent mortality. The cooler temperature favored fungal pathogenicity, with condial adhesion to the cuticle, germination and hemocoel invasion all significantly enhanced at 24 °C, compared with 34 °C. The wax moth larvae immune responses altered with the temperature, and with the infective dose of the fungus. Enzyme-based immune defenses (lysozyme and phenoloxidase) exhibited enhanced activity at the warmer temperature. A dramatic upregulation in the basal expression of galiomicin and gallerimycin was triggered by cooling, and this was augmented in the presence of the fungus. Profiling of the predominant insect epicuticular fatty acids revealed a 4-7 fold increase in palmetic, oleic and linoleic acids in larvae maintained at 24 °C compared with those at 34 °C, but these failed to exert fungistatic effects on topically applied fungus. This study demonstrates the importance of choosing environmental conditions relevant to the habitat of the insect host when determining the dynamics and outcome of insect/fungus interactions, and has particular significance for the application of entomopathogens as biocontrol agents.
authors.affiliation: Institute of Systematics and Ecology of Animals, Siberian Branch of Russian Academy of Science, Novosibirsk, Russia.
authors.forename: Vadim Y
authors.initials: VY
authors.lastname: Kryukov
authors.affiliation: Institute of Systematics and Ecology of Animals, Siberian Branch of Russian Academy of Science, Novosibirsk, Russia.
authors.forename: Olga N
authors.initials: ON
authors.lastname: Yaroslavtseva
authors.affiliation: Institute of Life Science, College of Medicine, Swansea University, Swansea, Wales, UK.
authors.forename: Miranda M A
authors.initials: MMA
authors.lastname: Whitten
authors.affiliation: Institute of Systematics and Ecology of Animals, Siberian Branch of Russian Academy of Science, Novosibirsk, Russia.
authors.forename: Maksim V
authors.initials: MV
authors.lastname: Tyurin
authors.affiliation: Department of Biosciences, College of Science, Swansea University, Swansea, Wales, UK.
authors.forename: Katherine J
authors.initials: KJ
authors.lastname: Ficken
authors.affiliation: Department of Biosciences, College of Science, Swansea University, Swansea, Wales, UK.
authors.forename: Carolyn
authors.initials: C
authors.lastname: Greig
authors.affiliation: Institute of Life Science, College of Medicine, Swansea University, Swansea, Wales, UK.
authors.forename: Nadja R
authors.initials: NR
authors.lastname: Melo
authors.affiliation: Institute of Systematics and Ecology of Animals, Siberian Branch of Russian Academy of Science, Novosibirsk, Russia.
authors.forename: Viktor V
authors.initials: VV
authors.lastname: Glupov
authors.affiliation: Institute of Systematics and Ecology of Animals, Siberian Branch of Russian Academy of Science, Novosibirsk, Russia.
authors.forename: Ivan M
authors.initials: IM
authors.lastname: Dubovskiy
authors.affiliation: Department of Biosciences, College of Science, Swansea University, Swansea, Wales, UK.
authors.forename: Tariq M
authors.initials: TM
authors.lastname: Butt
mesh_terms: D000818:Animals; D023082:Defensins / Q000378:metabolism; D005227:Fatty Acids / Q000502:physiology; D054884:Host-Pathogen Interactions; D052981:Metarhizium / Q000502:physiology*; D014442:Monophenol Monooxygenase / Q000378:metabolism; D009036:Moths / Q000382:microbiology*; D009113:Muramidase / Q000378:metabolism; D010572:Pest Control, Biological; D013172:Spores, Fungal / Q000502:physiology
chemical_list: D023082:Defensins; D005227:Fatty Acids; C512107:gallerimycin; D014442:Monophenol Monooxygenase; D009113:Muramidase
keywords: Metarhizium; biocontrol; entomopathogenic fungus; immunity; temperature