Collaborative Research: Production and Dynamics of DMSP and Related Compounds in Response to Oxidative Stress in Marine Phytoplankton

合作研究：海洋浮游植物氧化应激反应中 DMSP 及相关化合物的产生和动态

• 批准号: 0221106
• 负责人: David Kieber
• 金额: $ 27.65万
• 依托单位: SUNY College of Environmental Science and Forestry
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-09-01 至 2006-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0221106&HistoricalAwards=false
• 关键词: Collaborative; Research; Production; Dynamics; DMSP

Oxidative stress is a pervasive problem for oxygen-evolving plants, and is likely to be especially important for marine phytoplankton growing in nutrient-impoverished waters with high fluxes of visible and ultraviolet (UV) solar radiation. Very little is known about how marine algae cope with oxidative stress. In this study, a new hypothesis is presented that dimethylsulfoniopropionate (DMSP) is a unique and very important antioxidant in the ocean that serves as a primary defense in combatting and alleviating oxidative stress. Its role as an antioxidant is likely because DMSP is the dominant cellular sulfur compound in, and a major organic constituent of many marine algae worldwide. Furthermore, preliminary results indicate that DMSP and its enzymatic lysis product, DMS are highly effective scavengers of toxic reactive oxygen species (e.g., hydroxyl radicals) in cells, removing these species faster, in some cases, than the well documented antioxidants, ascorbic acid and glutathione. DMSP and DMS oxidation yield dimethylsulfoxide (DMSO), which is also an effective oxidant scavenger as is acrylate, the other product of DMSP lysis. Together, these related compounds should serve as a multifunctional, highly flexible antioxidant system in DMSP-containing algae. To investigate this DMSP antioxidant system, the following related hypotheses are being tested by this research team: 1) Intracellular DMSP concentrations in phytoplankton will increase in response to chronic oxidative stress, and will decrease in response to acute oxidative stress. 2) Turnover of cellular DMSP is induced by oxidative stress, resulting in increased production of putative antioxidants. 3) Phytoplankton with high DMSP content and high DMSP lyase activity will be more resistant to oxidative stress than phytoplankton with low DMSP or low lyase activity. To test these hypotheses, axenic cultures of ecologically-important phytoplankton species and natural seawater populations are being exposed to various forms of oxidative stress, including high photon fluxes of visible light (400-700 nm) and/or UV radiation (290-400 nm), nutrient limitation (Fe and N), and addition of paraquat or copper. During these exposures, changes in cellular DMSP and related compounds will be determined along with DMSP lyase activity. Complementary measurements of other antioxidant defense systems (e.g., ascorbate, reduced and oxidized glutathione, ascorbate peroxidase, superoxide dismutase) will provide information on how the DMSP system varies in relation to these well-established antioxidant defenses. This project will elucidate the mechanisms that control DMSP levels in the ocean and its rate of conversion to DMS, which is globally-significant because of the important role of DMS in atmospheric chemistry and, possibly, climate. If the DMSP antioxidant hypothesis is correct, then an important, hitherto unknown, cellular function of DMSP will have been identified. Understanding the cellular physiology of DMSP and its relationship to other poorly-understood algal antioxidant systems will increase our understanding of the factors that control the distribution of ecologically-important phytoplankton in the sea. This study will also result in the interdisciplinary training of advanced undergraduate and graduate students in algal physiological ecology and oceanography. The PIs and students will disseminate results of this study through scholarly and public presentations, scientific journals, popular articles and freely-accessible web pages.

氧化应激对于产氧植物来说是一个普遍存在的问题，对于在可见光和紫外线 (UV) 太阳辐射高通量的营养贫乏水域中生长的海洋浮游植物来说可能尤其重要。 人们对海藻如何应对氧化应激知之甚少。 在这项研究中，提出了一个新的假设，即二甲基磺基丙酸酯（DMSP）是海洋中一种独特且非常重要的抗氧化剂，可作为对抗和减轻氧化应激的主要防御手段。 其作为抗氧化剂的作用可能是因为 DMSP 是全球许多海藻中主要的细胞硫化合物，也是其主要有机成分。 此外，初步结果表明，DMSP 及其酶裂解产物 DMS 是细胞中有毒活性氧（例如羟基自由基）的高效清除剂，在某些情况下，比有据可查的抗氧化剂、抗坏血酸和谷胱甘肽更快地清除这些物质。 DMSP 和 DMS 氧化产生二甲亚砜 (DMSO)，它与 ​​DMSP 裂解的另一种产物丙烯酸酯一样，也是一种有效的氧化剂清除剂。 这些相关化合物一起应在含 DMSP 的藻类中充当多功能、高度灵活的抗氧化系统。 为了研究DMSP抗氧化系统，该研究小组正在测试以下相关假设：1）浮游植物细胞内DMSP浓度会因慢性氧化应激而增加，并会因急性氧化应激而降低。 2) 细胞 DMSP 的更新是由氧化应激诱导的，导致假定的抗氧化剂的产生增加。 3）高DMSP含量和高DMSP裂解酶活性的浮游植物比低DMSP或低裂解酶活性的浮游植物更能抵抗氧化应激。 为了检验这些假设，对生态重要的浮游植物物种和天然海水种群的无菌培养物正暴露于各种形式的氧化应激，包括可见光（400-700 nm）和/或紫外线辐射（290-400 nm）的高光子通量、营养限制（Fe和N）以及添加百草枯或铜。 在这些暴露过程中，细胞 DMSP 和相关化合物的变化以及 DMSP 裂解酶活性将被确定。 其他抗氧化防御系统（例如，抗坏血酸、还原型和氧化型谷胱甘肽、抗坏血酸过氧化物酶、超氧化物歧化酶）的补充测量将提供有关 DMSP 系统如何与这些完善的抗氧化防御相关的变化的信息。 该项目将阐明控制海洋中 DMSP 水平及其转化为 DMS 的速率的机制，由于 DMS 在大气化学以及可能的气候中的重要作用，这具有全球意义。 如果 DMS​​P 抗氧化假说是正确的，那么 DMSP 的一个重要的、迄今为止未知的细胞功能将被确定。 了解 DMSP 的细胞生理学及其与其他知之甚少的藻类抗氧化系统的关系将增加我们对控制海洋中具有重要生态意义的浮游植物分布的因素的理解。这项研究还将对高级本科生和研究生进行藻类生理生态学和海洋学的跨学科培训。 PI 和学生将通过学术和公开演讲、科学期刊、热门文章和免费访问的网页来传播这项研究的结果。