IntBIO: Coordinating and integrating whole-plant responses to abiotic and biotic stress signals via changes in plasma membrane proteomes

农业生产依赖于在许多不同的环境条件下成功种植农作物。了解植物如何优先考虑和整合来自不同环境压力的信号对提高作物产量很重要，因为它可以帮助避免育种出对一种压力更有耐受性的植物，而无意中却对其他压力更敏感。本研究探讨了一种新发现的植物对细菌病原体的反应之间的相互作用，这种相互作用与植物对低营养物质的反应相交叉并改变了植物对低营养物质的反应，特别是铁，一种植物和人类必需的微量营养素。重要的是，这些数据表明，植物优先考虑对细菌病原体的反应，而不是低营养可用性。这项工作的目标是了解这两种环境信号是如何以及在植物的哪些部分整合在一起的。这一目标将通过汇集铁营养反应、细菌病原体反应、细胞生物学和植物信号的专业研究人员团队来实现，以检查单个细胞、特定组织以及叶和根之间的通信中发生的变化。单独检查任何一个方面——无论是只有一个应力还是只有一种组织类型——都只能提供对更大的综合过程的部分理解。除了阐明可以提高作物产量的以前未知的生物过程外，该项目还将为下一代科学家提供理想的培训环境，因为个体研究人员将在具有不同专业知识的实验室之间流动，对复杂的生物系统进行现代的多学科研究。铁响应转运蛋白1 （iron - responsive Transporter 1, IRT1）仅局限于根系，是植物从土壤中吸收铁的主要途径。质膜上的IRT1蛋白水平与植物的铁状态成反比。如果植物的铁含量较低，IRT1蛋白在PM积聚以增加铁的吸收；然而，如果铁水平足够，IRT1蛋白通过内吞去除而减少。研究小组最近发现，当植物受到细菌感染的挑战时，IRT1的水平会迅速下降，即使在应该增加IRT1的低铁条件下。此外，研究小组还发现了三种突变体，它们改变了植物的免疫反应，在低铁条件下，它们也大大降低了IRT1的水平。这些结果表明：(a)生物胁迫信号与铁信号相结合，(b)生物胁迫信号覆盖低铁信号。该项目的目标是确定这些信号如何以及在何处集成。由于铁传感主要发生在叶片中，并将未知信号传递到根以调节IRT1水平，因此本研究的一个重要方面将是确定生物胁迫信号是否改变叶片中的铁信号，直接影响根中的IRT1水平，或者以某种信号整合的组合起作用。这些可能性将通过结合突变体的细胞特异性互补测定以及仅用细菌激发子感染叶子或根来解决。在根或叶中整合转录组学和PM蛋白质组学分析将确定根和/或叶中其他铁响应转录物或蛋白质是否发生改变，潜在地揭示共同调节转录物/蛋白质的组织特异性网络，以及揭示三种突变体是否表现出相似或明显的差异，从而确定突变体在信号通路中的作用。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Agricultural production relies on successfully growing crop plants under many different environmental conditions. Understanding how plants prioritize and integrate signals from diverse environmental stresses is important for improving crop yields because it can help to avoid breeding plants that may be selected for a greater tolerance to one stress while inadvertently becoming more susceptible to others. This research investigates a newly discovered interaction between plant responses to bacterial pathogens that intersects with and modifies the plant’s responses to low nutrient availability, particularly iron, an essential micronutrient for plants and humans. Importantly, the data indicates that the plant prioritizes responses to bacterial pathogens over low nutrient availability. The goal of this work is to understand how and in which parts of the plant these two environmental signals are integrated. This goal will be accomplished by bringing together a team of researchers with expertise in iron nutritional responses, bacterial pathogen responses, cellular biology, and plant signaling, to examine changes that occur in individual cells, in specific tissues, and in communication between leaves and roots. Examining any one aspect alone – whether only one of the stresses or in only one tissue type – would only provide a partial understanding of the larger, integrated process. In addition to elucidating a previously unknown biological process that could improve crop yields, this project will provide an ideal training environment for the next generation of scientists as the individual researchers will move fluidly between laboratories with different expertise to conduct modern, multidisciplinary investigations of a complex biological system. Iron-Responsive Transporter 1 (IRT1) is localized only to roots and is the main path for iron uptake from the soil. IRT1 protein levels at the plasma membrane (PM) are inversely proportional to the iron status of the plant. If the plant’s iron levels are low, IRT1 protein accumulates at the PM to increase iron uptake; whereas if iron levels are sufficient, IRT1 protein decreases by endocytic removal. The research team recently found that when a plant is challenged by a bacterial infection, the levels of IRT1 rapidly decrease, even under low iron conditions that should increase IRT1. In addition, the team has identified three mutants that alter plant immune responses that also have greatly reduced levels of IRT1 under low iron conditions. These results indicate that (a) biotic stress signaling is integrated with iron signaling, and (b) that biotic stress signaling overrides low iron signaling. The goal of this project is to determine how and where these signals are integrated. Because iron sensing occurs primarily in leaves with an unknown signal being transmitted to the roots to regulate IRT1 levels, an important aspect of this research will be to determine if biotic stress signaling alters iron signaling in leaves, directly affects IRT1 levels in roots, or acts in some combination of signal integration. These possibilities will be addressed through a combination of cell-specific complementation assays of the mutants as well as infecting only leaves or only roots with bacterial elicitors. An integration of transcriptomic and PM proteomic analyses in either roots or leaves will determine if other iron-responsive transcripts or proteins are altered in roots and/or leaves, potentially revealing tissue-specific networks of co-regulated transcripts/proteins, as well as revealing whether the three mutants show similar or distinct differences, thus defining where the mutants may function in the signaling pathway(s).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.