The genus Arsenophonus represents one of the most widespread clades of insect endosymbionts, including reproductive manipulators and bacteriocyte-associated primary endosymbionts. Two strains belonging to the Arsenophonus clade have been identified as insect-vectored plant pathogens of strawberry and sugar beet. The bacteria accumulate in the phloem of infected plants, ultimately causing leaf yellows and necrosis. These symbionts therefore represent excellent model systems to investigate the evolutionary transition from a purely insect-associated endosymbiont towards an insect-vectored phytopathogen. Using quantitative PCR and transmission electron microscopy, we demonstrate that ‘Candidatus Phlomobacter fragariae’, bacterial symbiont of the planthopper Cixius wagneri and the causative agent of Strawberry Marginal Chlorosis disease, can be transmitted from an infected strawberry plant to multiple daughter plants through stolons. Stolons are horizontally growing stems enabling the nutrient provisioning of daughter plants during their early growth phase. Our results show that Phlomobacter was abundant in the phloem sieve elements of stolons and was efficiently transmitted to daughter plants, which rapidly developed disease symptoms. From an evolutionary perspective, Phlomobacter is, therefore, not only able to survive within the plant after transmission by the insect vector, but can even be transmitted to new plant generations, independently from its ancestral insect host.

中文翻译：

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跳过昆虫媒介：植物病原体'Ca的植物S传播。昆虫内生菌的Arsenophonus进化枝中的草莓红杆菌

Arsenophonus属是昆虫内共生体最广泛的进化枝之一，包括生殖操纵子和与细菌细胞相关的初级内共生体。已经确定了属于Arsenophonus进化枝的两种菌株是草莓和甜菜的昆虫媒介植物病原体。细菌在受感染植物的韧皮部积累，最终导致叶片发黄和坏死。因此，这些共生体代表了研究从纯昆虫相关内共生体向昆虫媒介植物病原体的进化过渡的优秀模型系统。使用定量PCR和透射电子显微镜，我们证明了“暂定Phlomobacter fragariae”，稻飞虱的细菌共生wixri Cixius和草莓边缘绿化病的病原体可以通过茎从受感染的草莓植物传播到多个子代植物。斯托隆是水平生长的茎，能够在子代植物的早期生长阶段为其提供养分。我们的研究结果表明，韧皮细菌在茎的韧皮部筛元素中含量丰富，并可以有效地传播给子代植物，后者迅速出现病害症状。因此，从进化的角度看，杆状杆菌不仅能够在昆虫载体传播后在植物内生存，而且甚至可以独立于其祖先的昆虫宿主而传播给新一代植物。