New insight into the transovarial transmission of the symbiont Rickettsia in whitefly
New insight into the transovarial transmission of the symbiont Rickettsia in whitefly
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对粉虱共生立克次体经卵巢传播的新见解
DOI：
10.1007/s11427-020-1801-7
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
刘树生
中科院分区：
文献类型：
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作者：
单红伟;刘银泉;栾军波;刘树生
内共生菌通过卵传给下一代寄主已被认为是其在昆虫寄主中持续存在的主要策略，但其传播机制尚未阐明。在这里，我们描述了在全球重要的害虫烟粉虱卵子发生和胚胎发生过程中立克次体在卵巢和卵子中的动态位置。烟粉虱田间种群有很高的立克次体感染率，在所有感染立克次体的个体中，细菌都分布在寄主的体腔内，尤其是中肠、脂肪体、血细胞、血淋巴和细菌细胞附近。在卵子发生过程中，立克次体在卵巢中的分布是动态变化的，我们的超微结构观察表明，在发育早期，立克次体通过两条途径感染寄主卵巢：(I)通过内吞作用侵入滋养室，然后通过营养索传播到卵黄室；(Ii)通过劫持细菌细胞易位进入卵黄室。在卵子发生后期，大多数立克次体在卵母细胞胞质中降解。然而，少数存在于成熟卵黄膜下，扩散到胚胎中，并在胚胎发生期间增殖，以维持高保真的传递给下一代。我们的发现为支持昆虫共生体持续和传播的母体传播提供了新的见解。
Endosymbiont transmission via eggs to future host generations has been recognized as the main strategy for its persistence in insect hosts; however, the mechanisms for transmission have yet to be elucidated. Here, we describe the dynamic locations ofRickettsiain the ovarioles and eggs during oogenesis and embryogenesis in a globally significant pest whiteflyBemisia tabaci. Field populations of the whitefly have a high prevalence ofRickettsia, and in all Rickettsia-infected individuals, the bacterium distributes in the body cavity of the host, especially in the midgut, fat body, hemocytes, hemolymph, and near bacteriocytes. The distribution ofRickettsiawas subjected to dynamic changes in the ovary during oogenesis, and our ultrastructural observations indicated that the bacteria infect host ovarioles during early developmental stages via two routes: (i) invasion of the tropharium by endocytosis and then transmission into vitellarium via nutritive cord and (ii) entry into vitellarium by hijacking bacteriocyte translocation. Most of theRickettsiaare degraded in the oocyte cytoplasm in late-stage oogenesis. However, a few reside beneath the vitelline envelope of mature eggs, spread into the embryo, and proliferate during embryogenesis to sustain high-fidelity transmission to the next generation. Our findings provide novel insights into the maternal transmission underpinning the persistence and spread of insect symbionts.