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Parasites as Biological Weapons: How Microsporidia Might Be Facilitating the Invasive Success of the Ladybird Harmonia axyridisAndreas Vilcinskas1, Heiko
Vogel2 The harlequin ladybird Harmonia axyridis has emerged as an invasive species that outcompetes and threatens native ladybird species and displays high pathogen and parasite resistance. We discovered that H. axyridis has become resistant against microsporidia, obligate intracellular parasites it harbors in its hemolymph. These microsporidia wil kill native ladybirds such as Coccinella septempunctata both upon predation of H. axyridis eggs or larvae and upon experimental injection of spores isolated from hemolymph of H. axyridis. The identified novel microsporidia species can, therefore, be considered as a biological weapon against intraguild predators which may contribute to the remarkable invasive success of the harlequin ladybird. We also purified in hemolymph of H. axyridis, a secondary metabolite called harmonine. This compound displays a strong activity against a broad spectrum of pathogens and parasites. Strikingly, next generation-sequencing of the H. axyridis immunity-related transcriptome elucidated an impressive diversification of antimicrobial peptides. These findings invite studies addressing trade-offs and fitness-costs in investment in either innate immunity or chemical defenses. The overall goal of the project is to identify trade-offs, mechanisms and determinants of the interaction between H. axyridis, the microsporidia it harbors and conspecific ladybirds. Using an advanced set of methods and combining complementary analyses at biochemical (bioassays, proteomics), molecular (RNA-Seq, epigenetics analysis) and cellular (cell lines & toxicity assays) level, we aim to decipher the coevolution between H. axyridis and its microsporidia with emphasis on host adaptations providing resistance or tolerance against its own biological weapons. |
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