Division of Biological Sciences, University of Montana, Missoula, Montana 59812
Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599.
Genetics. 2020 Aug;215(4):1117-1132. doi: 10.1534/genetics.120.303330. Epub 2020 Jun 16.
Maternally transmitted bacteria infect about half of all insect species. They usually show imperfect maternal transmission and often produce cytoplasmic incompatibility (CI). Irrespective of CI, frequencies tend to increase when rare only if they benefit host fitness. Several , including Mel that infects , cause weak or no CI and persist at intermediate frequencies. On the island of São Tomé off West Africa, the frequencies of Mel-like infecting (Yak) and (San) fluctuate, and the contributions of imperfect maternal transmission, fitness effects, and CI to these fluctuations are unknown. We demonstrate spatial variation in Yak frequency and transmission on São Tomé. Concurrent field estimates of imperfect maternal transmission do not predict spatial variation in Yak frequencies, which are highest at high altitudes where maternal transmission is the most imperfect. Genomic and genetic analyses provide little support for effects on Yak transmission. Instead, rearing at cool temperatures reduces Yak titer and increases imperfect transmission to levels observed on São Tomé. Using mathematical models of frequency dynamics and equilibria, we infer that temporally variable imperfect transmission or spatially variable effects on host fitness and reproduction are required to explain Yak frequencies. In contrast, spatially stable San frequencies are plausibly explained by imperfect transmission, modest fitness effects, and weak CI. Our results provide insight into causes of Mel-like frequency variation in divergent hosts. Understanding this variation is crucial to explain spread and to improve Mel biocontrol of human disease in transinfected mosquito systems.
母体传播的细菌感染了大约一半的昆虫物种。它们通常表现出不完全的母体传播，并且经常产生细胞质不相容性 (CI)。无论是否存在 CI，如果它们有益于宿主适应性，那么稀有时频率往往会增加。包括感染 的 Mel 在内的几种细菌会导致较弱或没有 CI，并以中等频率持续存在。在西非的圣多美岛，感染 的类似于 Mel 的 （Yak）和 （San）的频率波动，并且不完全的母体传播、适应性影响和 CI 对这些波动的贡献是未知的。我们证明了 Yak 在圣多美岛的传播和传播存在空间变异。同时进行的不完全母体传播现场估计并不能预测 Yak 频率的空间变化，而 Yak 频率在高海拔地区最高，而在高海拔地区，母体传播最不完善。基因组和遗传分析几乎没有提供 Yak 传播的影响的支持。相反，在凉爽的温度下饲养会降低 Yak 的滴度，并增加不完全传播到在圣多美岛观察到的水平。我们使用 频率动态和平衡的数学模型推断，需要暂时可变的不完全传播或对宿主适应性和繁殖的空间可变影响来解释 Yak 频率。相比之下，空间稳定的 San 频率很可能可以通过不完全的传播、适度的适应性影响和较弱的 CI 来解释。我们的研究结果为不同宿主中类似于 Mel 的频率变化的原因提供了深入的了解。理解这种变化对于解释 的传播以及改善在转感染蚊子系统中 Mel 对人类疾病的生物控制至关重要。
