RUI Collaboraitve Research: Mechanisms of induced pathogen resistance in seagrasses

海草容易受到迷路菌属（迷路菌门）网状原生生物的攻击。这些无处不在的腐生或弱寄生生物可以周期性地变成致命的病原体，导致这些沙草萎缩性疾病，并导致种群数量突然下降。这些科学家认为，海草种群对迷路虫攻击的易感性差异是由于不断变化的环境条件改变了海草通过莽草酸/苯基丙烯（SA/PP）途径产生酚类化合物来维持或发展抗病性的能力。海草叶片和嫩枝中酚类化合物的浓度是与抗萎蔫病有关的唯一特征。以往的研究表明，某些物种的抗病性与酚酸和其他聚合酚类物质的含量有关，酚类物质可以通过迷路菌的攻击和/或伤害诱导产生，海草酚类物质在培养中抑制了该病原体的生长。虽然海草酚类物质与抗病性之间存在关联的证据是相关的，并且来自相对较少的对有限数量物种的研究，但它表明，与迄今为止研究的所有陆生植物一样，海草对病原体的攻击表现出诱导防御。证据还表明，海草的反应涉及激活SA/PP途径，导致植物酚类物质的产生。然而，SA/PP通路的调控尚未在海草中得到研究，我们也不完全了解环境因素如何影响海草的抗病性。Drs。Arnold， Boettcher和Tanner将研究SA/PPpathway的调控和海草对迷路菌感染的抗性。具体来说，研究的目标是：(1)验证SA/PP通路关键酶受迷路虫攻击诱导的假设，(2)确定哪些酚类物质在SA/PP通路诱导下积累，(3)在体内测试酚酸/缩合单宁水平与海草抗性之间的联系，(4)确定SA/PP通路诱导和酚类化合物积累是否受到特定环境条件的影响，(5)验证这些条件之间的联系。SA/PP代谢的改变和海草对迷宫虫攻击的抵抗力的变化。这些问题将在热带/亚热带海草海草（Thalassia testudinum）和温带海草（Zostera marina）这两种海草的中生态种群中得到解决，这两种海草都受到周期性消耗性疾病爆发的影响，并表现出对病原体攻击和/或伤害的诱导产生酚类化合物的反应。SA/PP途径酶的活性、酚酸和聚合酚的浓度以及生理健康指标（生长、光合作用、碳水化合物和蛋白质的浓度）将在感染和无病原体的植物中进行检测。他们还将比较这些海草在不同环境条件下对感染的反应。最后，将使用特定SA/PP途径酶的人工抑制剂来确定植物在无法产生SA/PP酚类物质时抵抗迷路虫攻击的能力。

Seagrasses are susceptible to attack by net-forming protists within the genusLabyrinthula (Phylum Labyrinthulomycota). These ubiquitous, largely saprophytic orweakly parasitic organisms can periodically become virulent pathogens, causing theseagrass wasting disease and contributing to sudden population declines. These scientists suggest that differences in susceptibility of seagrass populations to Labyrinthula attack arise as changing environmental conditions alter the ability of seagrasses to maintain or develop disease resistance by the production of phenolic compounds via the shikimic acid /phenylpropenoid (SA/PP) pathway. The concentrations of phenolic compounds in seagrass leaves and shoots are the only characteristics that have been linked with resistance to the wasting disease. Previous studies indicate that, for certain species, disease resistance is correlated with the contentof phenolic acids and other polymeric phenolics, that phenolic production can be induced by Labyrinthula attack and/or wounding, and that seagrass phenolics inhibit the growth of this pathogen in culture. While the evidence for a link between seagrass phenolics and disease resistance is correlative and comes from relatively few studies on a limited number of species, it indicates that seagrasses, like all terrestrial plants examined to date, exhibit induced defenses against pathogen attack. The evidence also suggests that seagrass responses involve activation of the SA/PP pathway leading to the production of plant phenolics. However, the regulation of the SA/PP pathway has not yet been examined in seagrasses, and we do not fully understand how environmental factors may affect disease resistance in seagrasses. Drs. Arnold, Boettcher and Tanner will investigate the regulation of the SA/PPpathway and the resistance of seagrasses to infection by Labyrinthula. Specifically, thegoals of the research are: (1) to test the hypothesis that key SA/PP pathwayenzymes are induced by Labyrinthula attack, (2) to determine which phenolicsaccumulate in response to SA/PP pathway induction, (3) to test, in vivo, the link between phenolic acid / condensed tannin levels and seagrass resistance, (4) to determine whether SA/PP pathway induction and the accumulation of phenolic compounds are affected by specific environmental conditions, and (5) to test the proposed link between these conditions, altered SA/PP metabolism and changes in seagrass resistance to Labyrinthula attack. These questions will be addressed in mesocosm populations of two species, the tropical/subtropical seagrass Thalassia testudinum and the temperate seagrass Zostera marina, both of which are subject to periodic wasting disease outbreaks and exhibit induced production of phenolic compounds in response to pathogen attack and/or wounding. Activities of SA/PP pathway enzymes, concentrations of phenolic acids and polymeric phenols, and indicators of physiological health (growth, photosynthesis, concentrations of carbohydrates and proteins) will be examined in infected and pathogen-free plants. They will also compare the responses of these seagrasses to infection underdifferent environmental conditions. Finally, artificial inhibitors of specific SA/PPpathway enzymes will be used to determine the ability of plants to resist Labyrinthulaattack when they are unable to produce SA/PP phenolics.