Data from: Mitochondria and Wolbachia titers are positively correlated during maternal transmission

Mothers provide their offspring with symbionts. Maternally transmitted, intracellular symbionts must disperse from mother to offspring with other cytoplasmic elements, like mitochondria. Here, we investigated how the intracellular symbiont Wolbachia interacts with mitochondria during maternal transmission. Mitochondria and Wolbachia may interact antagonistically and compete as each population tries to ensure its own evolutionary success. Alternatively, mitochondria and Wolbachia may cooperate as both benefit from ensuring the fitness of the mother. We characterized the relationship between mitochondria and Wolbachia titers in ovaries of D. melanogaster. We found that mitochondria and Wolbachia titers are positively correlated in common laboratory genotypes of D. melanogaster. We attempted to perturb this covariation through the introduction of Wolbachia variants that colonize at different titers. We also attempted to perturb the covariation through manipulating the female reproductive tract to disrupt maternal transmission. Finally, we also attempted to disrupt the covariation by knocking down gene expression for two loci involved in mitochondrial metabolism: NADH dehydrogenase and a mitochondrial transporter. Overall, we find that mitochondria and Wolbachia titers are commonly positively correlated, but this positive covariation is disrupted at high titers of Wolbachia. Our results suggest that mitochondria and Wolbachia have likely evolved mechanisms to stably coexist, but the competitive dynamics change at high Wolbachia titers. We provide future directions to better understand how their interaction influences the maintenance of the symbiosis.

母体向其子代传递共生体。母系传播的胞内共生体必须与线粒体等其他细胞质组分一同完成从母体到子代的扩散。本研究旨在探究胞内共生体沃尔巴克氏体（Wolbachia）在母系传播过程中与线粒体的互作模式。

线粒体与沃尔巴克氏体可能存在拮抗互作并彼此竞争——二者均需通过种群策略保障自身的演化成功；二者也可能相互协作，通过保障母体适合度实现共同获益。

我们对黑腹果蝇（Drosophila melanogaster）卵巢内线粒体与沃尔巴克氏体的载量关系进行了表征分析。

研究发现，在常见的实验室饲养黑腹果蝇品系中，二者的载量呈正相关。我们通过引入定植载量各异的沃尔巴克氏体变体，尝试打破这一协变关系；此外，我们还通过操控雌性生殖道以干扰母系传播的方式，试图破坏二者的载量关联；最后，我们还通过敲低参与线粒体代谢的两个基因座——烟酰胺腺嘌呤二核苷酸脱氢酶（NADH dehydrogenase）与线粒体转运体（mitochondrial transporter）的表达，来瓦解二者的协变模式。

总体而言，我们观察到线粒体与沃尔巴克氏体的载量普遍呈正相关，但在沃尔巴克氏体高载量条件下，这一正协变关系会被打破。研究结果表明，线粒体与沃尔巴克氏体可能演化出了稳定共存的机制，但当沃尔巴克氏体载量过高时，二者的竞争动态会发生改变。本研究为进一步探索二者的互作如何影响共生关系的维持提供了未来研究方向。