DISSERTATION RESEARCH: Supply-Side Regulation of Herbivore-Induced Phenolics in Plants

论文研究：植物中草食动物诱导的酚类物质的供给侧调节杰克·舒尔茨和托尼·谢弗酚类化合物是在所有植物中合成的碳基化合物。木质素是木材的主要成分，是一种酚类物质。除了木质素的结构作用外，许多其他酚类物质在所有植物的生活中都扮演着不同的角色，既是结构元素，也是防御元素。酚类产物的变化构成了植物病虫害研究中研究最多的一类“防御”。许多关于植物如何分配碳和营养资源的生态学理论假设，植物能够根据环境的变化，改变用于合成酚类物质的资源比例。世界上大多数碳通过生物合成途径导致酚类合成(一旦它在光合作用过程中被植物从大气中带走)。因此，这些途径是全球碳循环的关键组成部分。迄今为止的所有证据都表明，全球变化将加强这些生物合成途径的重要性。然而，植物对酚类物质产生的调控仍然知之甚少。这可能部分是因为植物用来合成酚类物质的两种生物合成途径传统上是分开研究的。莽草酸途径(SP)是芳香族氨基酸的来源，苯丙烷途径(PP)是防御和木质素的来源。大多数植物学家把重点放在PP的详细调控上，PP是这条管道中的第二条途径，而忽略了这些途径中的早期步骤。这项研究的核心假设是，酚类物质的调节是在SP内合成的“供给侧”完成的，即第一条途径，以及PP内的下游。通过一系列温室实验，本研究旨在确定植物如何协调调节这条合成管道的顶端和底端，即两种调节酶(DAHPS和PAL)。另一个正在探索的想法是，当植物改变其酚类生产时，它们能够利用储存的碳基途径中间体的池。通过比较模式草本植物烟草和模式木本植物杨树的酚类调节策略，本研究将有助于解释碳资源是如何在非常不同的植物中分配到这些重要途径和产物的。这一结果将阐明植物碳分配模式的调节和演变。这些信息将指出培育或改造植物以最大限度地为各种目的分配碳的方法，并将有助于更好地了解植物的生长、防御和生产力。

DISSERTATION RESEARCH: Supply-side Regulation of Herbivore-Induced Phenolics in PlantsJack Schultz and Toni SchaefferPhenolics are carbon-based chemicals synthesized within all plants. Lignin, the major component of wood, is a phenolic. In addition to the structural role of lignin, many other phenolics play diverse roles in the lives of all plants as both structural and defensive elements. Changes in phenolic production comprise the most-studied class of "defenses" in research on plant pests. Much ecological theory on how plants allocate their carbon and nutrient resources presumes that plants, in response to changes in their environment, are able to vary the proportion of their resources that they use to synthesize phenolics. The majority of the world's carbon passes through the biosynthetic pathways leading to phenolic synthesis (once it is taken from the atmosphere by the plant during photosynthesis). Hence, these pathways are critical components of global carbon cycling. All evidence to date suggests that global change will enhance the importance of these biosynthetic pathways. However, plant regulation of phenolic production is still poorly understood. This may be partly because the two biosynthetic pathways that plants use to synthesize phenolics have traditionally been studied separately. The shikimate pathway (SP) has been studied as the source of aromatic amino acids, and the phenylpropanoid pathway (PP) as the source of defenses and lignin. Most plant scientists have focused on the detailed regulation of the PP, the second pathway in this pipeline, ignoring earlier steps in these pathways. The core hypothesis of the proposed research is that regulation of phenolics is accomplished at the "supply-side" of synthesis within the SP, the first pathway, as well as downstream within the PP. Using a series of greenhouse experiments, this research aims to determine how plants coordinately regulate the "top" and "bottom" of this synthetic pipeline, namely two regulatory enzymes (DAHPS and PAL). Also being explored is the idea that plants are able to exploit stored pools of carbon-based pathway intermediates when they change their phenolic production. By comparing the phenolic regulation strategy of a model herbaceous plant, tobacco, to a model woody plant, poplar, this research will help explain how carbon resources are allocated to these important pathways and products in very different plants. The results will clarify the regulation and evolution of carbon allocation patterns in plants. This information will point to ways in which plants may be bred or engineered to maximize carbon allocation for various purposes, and will facilitate better understanding of plant growth, defense, and productivity.