• A dodder (Cuscuta) often simultaneously parasitizes two or more adjacent hosts. Phosphate (Pi) deficiency is a common stress for plants, and plants often interact with soil microbes, including arbuscular mycorrhizal fungi (AMF), to cope with Pi stress. Little is known about whether dodder transmits Pi deficiency-induced systemic signals between different hosts.
• In this study, dodder-connected plant clusters, each composed of two tobacco (Nicotiana tabacum) plants connected by a dodder, were established, and in each cluster, one of the two tobacco plants was treated with Pi starvation. AMF colonization efficiency, rhizosphere bacterial community, and transcriptome were analyzed in the other dodder-connected Pi-replete tobacco plant to study the functions of interplant Pi signals.
• We found that dodder transfers Pi starvation-induced systemic signals between host plants, resulting in enhanced AMF colonization, changes of rhizosphere bacterial communities, and alteration of transcriptomes in the roots of Pi-replete plants. Importantly, genetic analyses indicated that microRNA399s (miR399s) and strigolactones suppress the systemic Pi signals and negatively affect AMF colonization in the Pi-replete plants.
• These findings provide new insight into the ecological role of dodder in mediating host–host and host–microbe interactions and highlight the importance of strigolactone and miR399 pathways in systemic Pi signaling.

中文翻译：

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MicroRNA399s 和独脚金内酯介导菟丝子连接的寄主植物之间的系统磷酸盐信号传导，并控制寄主植物与根际微生物的关联

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  菟丝子 （Cuscuta） 通常同时寄生在两个或多个相邻的宿主上。磷酸盐 （Pi） 缺乏症是植物的常见压力，植物经常与土壤微生物相互作用，包括丛枝菌根真菌 （AMF），以应对 Pi 压力。关于菟丝子是否在不同宿主之间传递 Pi 缺陷诱导的全身信号知之甚少。
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  在这项研究中，建立了菟丝子连接的植物簇，每个簇由菟丝子连接的两种烟草 （Nicotiana tabacum） 植物组成，在每个簇中，两种烟草植物中的一种接受 Pi 饥饿处理。在另一株菟丝子连接的充满 Pi 的烟草植物中分析 AMF 定植效率、根际细菌群落和转录组，以研究植物间 Pi 信号的功能。
• 
  我们发现菟丝子在寄主植物之间传递 Pi 饥饿诱导的系统信号，导致 AMF 定植增强、根际细菌群落的变化以及 Pi 充满植物根部转录组的改变。重要的是，遗传分析表明，microRNA399s （miR399s） 和独脚金内酯抑制全身性 Pi 信号，并对 AMF 在充满 Pi 的植物中的定植产生负面影响。
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  这些发现为菟丝子在介导宿主-宿主和宿主-微生物相互作用中的生态作用提供了新的见解，并强调了独脚金内酯和 miR399 通路在全身性 Pi 信号传导中的重要性。