Collaborative Research: Competing Sinks as Constraints on Plant Defense Responses

植物通常通过激活复杂的防御反应来应对害虫和病原体的攻击，其中包括产生有毒或威慑性化学物质。然而，所有的植物组织对攻击的反应并不相同。在自然界中，植物防御的分布是不均匀的，而且众所周知难以预测，植物防御提供了抗病虫害和提高收获质量。最近，防御反应激活的关键第一步被发现。在杨树中，研究表明受伤的组织必须通过植物维管系统输入资源，在这种情况下是糖，以支持防御物质的产生。在这些树木中，受伤的组织改变了它们的新陈代谢，成为更强的“糖汇”，并从植物的其他地方吸取资源。因此，更强的糖汇有更强的防御反应，当糖流被中断时，防御反应就会消失。这一观察结果有助于解释为什么植物防御在自然界中分布不均匀。它还提出了几种控制植物产品水平的策略，包括那些来自农业重要物种的产品。该项目将确定伤害是否会增强其他植物物种和类型的“糖库”强度，包括草本植物和藤蔓植物，它们产生各种防御性物质，如单宁、生物碱、蛋白质和硫代葡萄糖苷。该项目涉及大规模实验，以验证许多不同的植物为应对攻击而改变糖和其他资源的长距离流动的假设。它还将研究自然界中扰乱糖流的因素，比如花和水果的发育，它们与受伤的组织竞争糖资源，或者同时受到多种昆虫或病原体的攻击。更广泛的影响这些研究的结果将提供深入了解影响植物抗虫害的因素，并可能被操纵以提高作物或树木的生产力。植物用来控制糖流的策略在农业中很重要，因为它们决定了生产和收获的时间和质量。所研究的机制也是植物固碳和释放的核心，并可能影响全球碳收支。结果将决定像杨树这样的树木是否可以改变以将额外的碳封存在地下。该项目将吸引来自两个不同的（大/小）机构的大量本科生进行跨学科、合作研究和推广（包括K-12学校）。

INTELLECTUAL MERITPlants often respond to attack by pests and pathogens by activating complex defense responses, which include the production of toxic or deterrent chemicals. However, all plant tissues are not equally responsive to attack. In nature the distribution of plant defenses, which provide pest and pathogen resistance and enhance harvest quality, is uneven and notoriously difficult to predict. Recently, a critical first step in the activation of defense responses was discovered. In poplar trees, it was shown that wounded tissues must import resources, in this case sugars, via the plant vascular system to support the production of defensive substances. In these trees, wounded tissues alter their metabolism, becoming stronger "sugar sinks" and drawing resources away from elsewhere in the plant. As a result, stronger sugar sinks have stronger defense responses which disappear whenever the flow of sugars is interrupted. This observation helps to explain why plant defenses are unevenly distributed in nature. It also suggests several strategies for manipulating levels of plant products, including those from agriculturally-important species. This project would determine if wounding boosts the "sugar sink" strength of other plant species and types, including herbs and vines producing a wide variety of defensive substances such as tannins, alkaloids, proteins, and glucosinolates. The project involves large-scale experiments to test the hypothesis that many different plants shift the long-distance flow of sugars and other resources in response to attack. It will also examine factors that would disrupt sugar flow in nature, such as the development of flowers and fruits which out-compete wounded tissues for sugar resources or the simultaneous attack by multiple insects or pathogens. BROADER IMPACTS Results of these studies will provide insight into factors that influence pest resistance of plants and may be manipulated to enhance crop or tree productivity. The strategies plants use to manipulate sugar flow are important in agriculture, since they determine both the timing and quality of production and harvest. The mechanisms studied are also central to carbon sequestration and release by plants and may impinge on the global carbon budget. Results should determine whether trees like poplar can be altered to sequester additional carbon belowground. The project will engage a substantial number of undergraduates from two contrasting (large/small) institutions in interdisciplinary, collaborative research and outreach (including K-12 schools).