Nitrogen-intensive Plastic Responses to Herbivory: Primary Role for a Secondary Metabolite

大多数研究人员认为，草食动物的生长在很大程度上受到植物含氮量的限制。当一种植物被吃掉时，它剩下的组织表现出过多的反应，不仅包括“次生”代谢物浓度的急剧增加(推测诱导的防御反应可能有助于植物对草食的抗性)，而且还包括一系列生理反应，包括光合作用速度的增加(这可能有助于植物对草食的弹性)。这项提案研究了植物如何整合这两套反应，从而询问植物如何解决其对食草动物攻击的“防御性”和“民用”生化反应的潜在冲突要求。这种代谢整合将在一种植物(烟草)中进行检验，在这种植物中，“防御”反应--产生有毒生物碱--和“民用”反应--包括光合作用能力--都对植物的氮素收支有很大的需求。由于氮经常是植物生长的重要限制元素，我们将安排氮在生物碱和蛋白质合成之间的移动，以检查这种代谢整合。农业中的抗虫性研究主要集中在两个方面：赋予植物抗虫害能力的化学和物理特性，以及与抗草食性有关的植物生理属性。几乎没有研究探索对食草动物的防御和容忍的整合。如果我们要超越“杀虫剂方法”来进行植物保护，对这种整合的理解是至关重要的。这将是第一个检查化学防御作为生理过程的组成部分的项目，植物通过这些过程再生失去给食草动物的组织。

The growth of herbivores is recognized by most researcher to be limited in large part by a plant's nitrogen content. When a plant is eaten, its remaining tissues exhibit a plethora of responses that include not only the dramatic increases in the concentrations of "secondary" metabolites (the putative induced defenses which presumably contribute to a plant's resistance to herbivory) but also a suite of physiological responses that include increases in photosynthetic rates( which presumably contribute to a plant's resilience to herbivory). This proposal examines how a plant integrates these two suites of responses and thus asks how a plant resolves the potentially conflicting demands of its "defensive" and "civilian" biochemical responses to herbivore attack. This metabolic integration will be examined in a species of plant (Nicotiana sylvestris) where both the "defensive" responses--the production of toxic alkaloids--and the "civilian" responses--included photosynthetic capacity--make large demands on a plant's nitrogen budget. Since nitrogen is frequently the important limiting element for plants growth, we will choreograph the movement of nitrogen between alkaloid and protein synthesis in order to examine this metabolic integration. Research on pest-resistance in agriculture has been focused on two fronts: the chemical and physical of plants that confer resistance to pest attack and the physiological attributes of plants associated with resilience to herbivory. Little, if any research has explored the integration of both the defense against and the tolerance to herbivory. And understanding of this integration is essential if we are to proceed beyond the "pesticide-approach" to plant protection. This will be the first project to examine chemical defense as an integral part of the physiological processes by which plants regrow those tissues lost to herbivores.