Plasmodesmata as regulators of the growth-defence trade-off

植物细胞与它们的邻居相连，进行通信和资源交换，这种相互连接使多细胞组织和器官之间的协调生长和反应成为可能。细胞与细胞的连接是通过胞间连丝实现的，胞间连丝是质膜内衬的“隧道”，其穿过细胞壁连接相邻细胞并在相邻细胞之间建立质膜和细胞质的连续性。胞间连丝有效地充当“闸门”来调节可溶性分子的通量，响应于一系列刺激而关闭和打开。排列在胞间连丝上的质膜在功能上与膜的其余部分不同，允许对它们的反应进行离散和独立的功能控制。胞间连丝通过启动导致其关闭的信号级联反应来响应许多应激信号，并且当细胞感知微生物威胁时，观察到这对于最佳免疫信号至关重要。除了有助于免疫应答之外，胞间连丝闭合还诱导细胞隔离，这必须限制诸如碳和与其他细胞过程相关的信号的资源交换。事实上，胞间连丝作为糖通过植物分布的关键通道，提高了胞间连丝关闭在糖被需要维持生长的背景下对碳分配产生重大影响的可能性。我们最近发现，与成熟叶片相比，嫩叶不会关闭它们的胞间连丝以响应微生物的感知。这支持了年轻组织优先考虑生长而不是防御的假设，保持胞间连丝开放以维持来自源组织的糖的流动以维持生长过程。这一点，以及观察到的plasmodesmal反应是独立调节，表明plasmodesmata是一个中心组成部分的机制，通过该机制的权衡之间的增长和国防是balanced.The建议将测试这个模型，确定是否plasmodesmal关闭是不同的调节在一系列的发展阶段，生理状态和压力context。我们将利用我们的知识，胞间连丝调节免疫反应的幅度和时间，配置如何胞间连丝操纵扰动的生长防御权衡在sink tissues.How胞间连丝可以差异响应必须依赖于本机执行的响应，因此，我们将探讨不同的蛋白质组成的胞间连丝的组织，做和不关闭他们的胞间连丝。此外，由于胞间连丝的结构已被证明与汇或源状态有一定的相关性，我们将分析胞间连丝的结构，以确定哪些功能定义胞间连丝的反应。因此，我们将确定所需的一个胞间连丝的机制要素，以应对压力。该提案将详细说明胞间连丝如何在免疫信号背景下调节碳分配，以及它们如何作为控制生长-防御权衡的信号中枢的组成部分发挥作用。除了免疫反应，碳分配的调节与一系列生理背景有关，因此，该提案将建立对碳资源如何分配和消耗的一般理解，并在植物生长，发育和环境反应中找到应用。

Plant cells are connected to their neighbours for communication and resource exchange, with this interconnectivity enabling co-ordinated growth and responses across multicellular tissues and organs. Cell-to-cell connectivity is enabled by plasmodesmata, plasma membrane-lined 'tunnels' that connect neighbouring cells across the cell wall and establish both plasma membrane and cytoplasmic continuity between neighbouring cells. Plasmodesmata effectively act as 'sluice gates' to regulate the flux of soluble molecules, closing and opening in response to a range of stimuli. The plasma membrane that lines plasmodesmata is functionally distinct from the rest of the membrane, allowing discrete and independent functional control of their responses. Plasmodesmata respond to many stress signals by initiating a signalling cascade that results in their closure, and this was observed to be critical for optimal immune signalling when cells perceive microbe threats. In addition to contributing to immune responses, plasmodesmal closure induces cellular isolation that must limit the exchange of resources such as carbon, and signals relevant to other cellular processes. Indeed, plasmodesmata act as a key passage through which sugar is distributed through a plant, raising the possibility that plasmodesmal closure carries significant consequences for carbon allocation in a context in which sugars are required to maintain growth. We recently discovered that by contrast with mature leaves, young leaves do not close their plasmodesmata in response to microbe perception. This supports the hypothesis that young tissues prioritise growth over defence, keeping plasmodesmata open to maintain the flow of sugar from source tissues to sustain growth processes. This, and the observation that plasmodesmal responses are independently regulated, suggests plasmodesmata are a central component of the mechanism by which the trade-off between growth and defence is balanced.The proposal will test this model, determining whether plasmodesmal closure is differently regulated across a range of developmental stages, physiological states and stress contexts. We will exploit our knowledge that plasmodesmata regulate the amplitude and timing of immune responses, to profile how plasmodesmal manipulation perturbs the growth-defence trade-off in sink tissues.How plasmodesmata can differentially respond must depend on the machinery present to execute a response and therefore we will characterise the different protein composition of plasmodesmata in tissues that do and do not close their plasmodesmata. Further, as the structure of plasmodesmata has been shown to have some correlation with the sink or source status, we will profile plasmodesmal structure to identify what features define plasmodesmal responsiveness. Thus, we will define the mechanistic elements required for a plasmodesma to respond to stress. This proposal will detail how plasmodesmata regulate carbon allocation in an immune signalling context and how they function as a component of the signalling hub that controls the growth-defence trade-off. Beyond immune responses, regulation of carbon allocation is relevant to a range of physiological contexts and this proposal will therefore establish general understanding of how carbon resources are partitioned and consumed, finding application across plant growth, development and environmental responses.