Geographic origin and Wolbachia infection influence Aedes aegypti stress tolerance

Aedes aegypti mosquitoes carrying self-spreading, virus-blocking Wolbachia bacteria are being deployed to suppress dengue transmission. Aedes aegypti are widespread across tropical and subtropical regions but their adaptation to local climate conditions is poorly understood. Wolbachia-infected Ae. aegypti are sensitive to environmental conditions, likely contributing to the variable Wolbachia establishment success across release zones in different climates. With releases of Wolbachia-infected Ae. aegypti taking place in the hot and arid city of Jeddah, Saudi Arabia, it is important to understand the interaction between Wolbachia infections and genetic background within this local context. We introduced two Wolbachia transinfections (wAlbB and wMelM) into Ae. aegypti laboratory populations originating from Cairns, Australia and Jeddah, Saudi Arabia. Both wAlbB and wMelM showed complete maternal transmission and reduced infection and dissemination of dengue virus (DENV2) in Saudi Arabian Ae. aegypti, demonstrating their suitability for field release. We then assessed the contributions of genetic background and Wolbachia infection to desiccation, storage and heat stress tolerance. Saudi Arabian Ae. aegypti had lower egg viability but higher adult desiccation tolerance than Australian mosquitoes, with a slower rate of water loss in males, likely reflecting adaptation to local conditions. Wolbachia infection reduced adult heat tolerance in one background and egg viability in both backgrounds, particularly when eggs were exposed to high temperatures or stored before hatching. We also observed differential thermal stability between Wolbachia strains and severe fitness costs of wAlbB infection in females hatching from stored eggs. Wolbachia effects were similar across mosquito backgrounds, but the background effects themselves are expected to influence Wolbachia invasion dynamics, reinforcing the need to use local genotypes for mosquito release programs.

携带自我传播、病毒阻断型沃尔巴克氏体（Wolbachia）的埃及伊蚊（Aedes aegypti）已被用于抑制登革热的传播。埃及伊蚊广泛分布于热带与亚热带区域，但学界对其适应局地气候条件的机制尚不清楚。感染沃尔巴克氏体的埃及伊蚊对环境条件较为敏感，这大概率是导致不同气候区释放区域中沃尔巴克氏体定殖成功率存在差异的关键因素。随着感染沃尔巴克氏体的埃及伊蚊释放工作在沙特阿拉伯炎热干旱的城市吉达启动，明确该局地情境下沃尔巴克氏体感染与蚊类遗传背景之间的相互作用至关重要。本研究将wAlbB与wMelM两种沃尔巴克氏体转染菌株，分别引入源自澳大利亚凯恩斯与沙特阿拉伯吉达的埃及伊蚊实验种群。结果显示，在沙特阿拉伯来源的埃及伊蚊中，wAlbB与wMelM均表现出完全的母系传播能力，并可有效降低登革病毒2型（DENV2）的感染与播散，证实二者具备田间释放的应用潜力。随后，我们评估了遗传背景与沃尔巴克氏体感染对蚊类耐干燥、贮藏及热胁迫能力的影响。相较于澳大利亚来源的埃及伊蚊，沙特阿拉伯来源的埃及伊蚊虫卵存活率更低，但成虫耐干燥能力更强，雄性个体的水分流失速率更缓慢，这一特征大概率反映了其对当地干旱炎热环境的适应性演化。沃尔巴克氏体感染会降低特定遗传背景下成虫的耐热性，同时降低两种遗传背景下的虫卵存活率；尤其当虫卵暴露于高温环境或孵化前进行贮藏时，该抑制效应更为显著。此外，我们还观察到不同沃尔巴克氏体菌株的热稳定性存在显著差异，且wAlbB感染对从贮藏虫卵中孵化的雌性个体存在严重的适合度代价。整体而言，沃尔巴克氏体对蚊类的影响在不同遗传背景下表现相似，但遗传背景本身会对沃尔巴克氏体的种群入侵动态产生显著影响，这进一步强调了在蚊类生物防治释放项目中采用本地基因型的必要性。