菟丝子介导寄主间磷系统性信号对寄主根际微生物的影响

菟丝子是农业和林业上重要的寄生性杂草，能够同时寄生多个寄主，并在不同寄主间传递多种信号。磷缺乏是植物经常面临的逆境，且低磷胁迫可以改变植物与根际微生物的互作。我们前期工作发现，菟丝子能够介导磷系统性信号在不同寄主间的传递，并引起寄主独脚金内酯合成相关基因的变化，但其传递的生态学意义如何，仍缺乏研究。在本项目中，我们将利用菟丝子连接两个烟草寄主，对其中一个寄主进行磷胁迫处理，测定另一个寄主根际菌群和丛枝菌根真菌共生效率，并获得寄主生长相关数据，从而明确菟丝子介导的寄主间磷系统性信号对寄主根际微生物的影响，探讨系统性信号对寄主磷吸收和生长的调控作用。此外，我们将利用磷信号途径miR399和独脚金内酯合成途径ccd8的烟草为遗传材料，揭示菟丝子传递的磷系统性信号的调控机制。本项目对了解寄生植物-寄主-微生物三者的复杂互作有较重要意义，也将丰富我们对寄生植物生态功能的了解。

Dodder (Cuscuta) is a stem holoparasitic plant, and it is an important parasitic weed in agriculture and forestry. A dodder often simultaneously connects multiple hosts to form a “Cuscuta-connected plant cluster”. It has been found that in these plant clusters, dodder mediates the transmission of insect herbivory, salt stress, and nitrogen stress-related systemic signals between hosts. However, whether dodder also mediates phosphate systemic signals and the ecological significance are still unknown. Previously we found that dodder can mediate phosphate systemic signals between hosts and these signals cause changes of strigolactone-related gene expression in the hosts. Based on these results, we will use different tobacco hosts with dodders and determine when one host suffers from low phosphate stress, whether the rhizosphere microbiome and colonization of arbuscular mycorrhizal fungi will be affected in the phosphate-normal tobacco host, and we will study if the phosphate stress-induced systemic signals influence host phosphate assimilation and growth and development. In addition, using genetically modified tobacco in which miR399 and strigolactone pathway are silenced, we will study the functions of these pathways in controlling dodder-mediated phosphate systemic signaling. This project is necessary for understanding the complex interactions in the parasitic plant-host plant-microbiome system and provides new insight into the ecological functions of parasitic plants.