Plasmodesmata and chloroplasts in integrative defense signaling

阻止传染病传播的最有效方法之一是自我隔离。然而，当自我隔离没有在正确的时机发生时，疾病的传播可能会变得难以控制。无论是动物还是植物系统，在细胞水平上也是如此。一旦成功识别了入侵的病原体，宿主细胞就会部署防御程序来击退病原体。这通常涉及一种称为程序性细胞死亡的现象，这是一种有效的免疫反应。然而，如果一个细胞或一组细胞在没有适当沟通以使相邻细胞存活的情况下经历细胞死亡，可能会导致整个有机体的意外死亡。因此，了解细胞如何调节细胞死亡或健康信号的传递，不仅对增进我们的知识至关重要，而且有助于设计新的方法来提高宿主免疫力。在植物中，叶绿体产生各种免疫信号，众所周知，叶绿体和称为胞间连丝的细胞间桥对植物的防御至关重要。通过该项目提出的多学科研究，研究团队旨在研究植物中受感染的细胞如何将叶绿体免疫信号传递到胞间连丝，并与周围细胞进行沟通，以便在正确的时间和正确的地点差异化地传递死亡和健康信号。这些研究将使用最先进的活细胞成像技术和基因编码的荧光传感器引入到叶绿体迁移率或胞间连结功能改变的突变植物中。一旦病原体感染，植物可以引发超敏反应(HR)，触发受感染细胞的程序性细胞死亡(PCD)，同时保护周围细胞的健康。HR-PCD是一种高效的植物免疫形式，可以潜在地为提高农业生产力带来新的解决方案，而不严重依赖杀菌剂。然而，目前尚不清楚HR-PCD是如何被感染部位内和附近的细胞所包含的。在这里，研究小组建议探索HR-PCD细胞和它们周围的健康细胞之间的信号传递。具体地说，他们将把重点放在过氧化氢(H2O2)上，这是HR-PCD所需的一种关键类型的活性氧(ROS)。该团队将跟踪细胞内叶绿体中爆发的过氧化氢是如何传递的，以限制分子通过连接HR-PCD部位内的细胞和周围健康细胞的胞间连丝的运动。主要研究目标包括：1)建立H_2O_2猝发与PD状态之间的时间线；2)研究PD时局部H_2O_2猝发的可能性；3)探索HR-PCD细胞内外PD的调节模式。该研究小组设想首次提供高分辨率、实时的胞间连丝渗透性图，显示叶绿体-胞间连丝如何在细胞内和胞间发生相互作用。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

One of the most effective ways to stop spreading a contagious disease is self-isolation. However, when self-isolation does not happen at the right timing, the spread of disease could go unruly. This is also true at the cellular level whether it concerns an animal or plant system. Upon a successful recognition of invading pathogen, host cells deploy defense programs to fight off pathogens. This often involves a phenomenon called programmed cell death, which is an effective immune response. However, if a cell or group of cells undergo cell death without appropriately communicating for neighboring cells to survive, it could result in an unwanted death of the whole organism. Therefore, understanding how cells regulate the relay of cell death or health signal is not only critical to advance our knowledge but also to help engineer new ways to boost host immunity. In plants, various immune signals are produced in chloroplasts, and it is known that both chloroplasts and the intercellular bridges called plasmodesmata are vital for plant defense. Through multi-disciplinary research proposed in this project, the research team aims to investigate how infected cells in plants might deliver chloroplastic immune signals to plasmodesmata and communicate with their surrounding cells to differentially relay death and health signals at the right time and right place. These investigations will be performed using state-of-the-art live-cell imaging techniques and genetically encoded fluorescent sensors introduced into mutant plants that are altered in chloroplasts mobility or plasmodesmal function.Upon pathogen infection, plants can elicit the hypersensitive response (HR), triggering programmed cell death (PCD) of the infected cells while preserving the health of the surrounding cells. HR-PCD is a highly effective form of plant immunity that can potentially lead to new solutions for boosting agricultural productivity without relying heavily on biocides. However, it remains unknown how HR-PCD is contained to just those cells within and near the infection sites. Here, the research team proposes to explore the signal relay between the HR-PCD cells and the healthy cells bordering them. Specifically, they will focus on hydrogen peroxide (H2O2), which is a key type of reactive oxygen species (ROS) required for HR-PCD. The team will track how the H2O2 burst from intracellular chloroplasts is delivered to restrict molecular movement through the plasmodesmata connecting cells within the HR-PCD site and healthy cells surrounding it. Major research aims include: 1) Establishing the timeline between H2O2 burst and PD status; 2) Investigating the potential of a localized H2O2 burst at PD; 3) Exploring the modes of PD regulation within and outside HR-PCD cells. The research team envisions delivering, for the first time, a high-resolution, real-time plasmodesmal permeability map displaying how chloroplast-plasmodesmata interactions may occur at the intra- and intercellular levels.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.