NSF Young Investigator

9357302科尔曼大气中二氧化碳和其他温室气体的浓度继续上升。这可能导致全球平均温度的上升，以及每年甚至每天的温度变化。温度变化增加的一个后果是，植物可能会比现在更频繁地暴露于突然而严重的温度升高（即热冲击）。植物承受这些高温事件的能力很可能与它们提高某些热休克蛋白（hsps）水平的能力有关，至少部分有关。关于这些蛋白质在植物中的分子生物学研究已经有了大量的资料。然而，关于细胞或整个植物在施加热胁迫之前的生理状态如何影响热休克蛋白的合成和积累或植物在热胁迫下生存的能力，人们知之甚少。美国国家科学基金会青年研究者奖支持在不同碳、光和氮可用性的环境中使用几种基因型的东部棉杨（杨树）进行研究，从而使植物具有不同的生理状态。然后将这些植物暴露在温度急剧升高、慢性亚致死温度胁迫或控制条件下，以回答以下问题。(1)植物的生理状态如何影响单个急性热休克反应中特定胁迫蛋白的积累动力学和程度，以及长时间高温事件和正常蛋白合成的恢复速度？(2)在急性和慢性热应激期间和之后，叶片中热休克蛋白的合成和积累模式与光合机构的功能有何关系？(3)胁迫蛋白的合成是否代替了光合酶的产生或激活？(4)氮的限制是否加剧了权衡？(5)在细胞水平上胁迫蛋白生产的动态与整个植株的生产性能之间是否存在相关性？(6)这些关系如何受到植物发育阶段或植物基因型的影响？这项工作的结果很重要，原因有很多。首先，全球气候模式预测，未来大气中的二氧化碳浓度将极高，二氧化碳的积累以及其他因素可能导致温度模式受到极端波动的影响。此外，二氧化碳含量的增加，就其本身而言，将对植物的生理状态产生实质性的影响。因此，了解植物在高二氧化碳环境下的应激反应是如何改变的，将是了解农业和自然环境下植物如何对预测的全球气候变化做出反应的重要一步。其次，应激蛋白在获得应激耐受性中的作用正处于激烈的争论之中。了解植物生理状态在控制热休克反应中的作用，可能为了解胁迫蛋白何时以及是否在促进植物组织的胁迫耐受性中起作用提供重要的联系。* * *

9357302 Coleman Atmospheric concentrations of carbon dioxide and other greenhouse gases continue to rise. This may lead to increases in the mean global temperature as well as in yearly, and even daily, variations in temperature. One consequence of increasing variation in temperatures is that plants may be exposed to sudden and severe increases of temperature (i.e., heat shocks) at a greater frequency than they are now. The ability of plants to withstand these hyperthermic episodes is most likely related, at least in part, to their capacity for elevating levels of certain heat shock proteins (hsps). A great deal of information regarding the molecular biology of these proteins in plants exists. Yet, little is known regarding how the physiological state of the cell or whole-plant prior to the imposition of heat stress affects the synthesis and accumulation of hsps or the ability of plants to survive heat stress. This NSF Young Investigator Award supports research using several genotypes of eastern cottonwood (Populus deltoides) in environments with different availabilities of carbon, light and nitrogen resulting in plants with different physiological states. These plants will then be exposed to acute increases in temperature, to chronic sub-lethal temperature stress, or to control conditions to answer the following questions. (1) How does the physiological state of the plant affects the kinetics and extent of accumulation of specific stress proteins in response to a single acute heat shock, as well as a prolonged high- temperature event and the recovery rate of normal protein synthesis? (2) How are patterns of heat shock protein synthesis and accumulation in leaves correlated to the functioning of the photosynthetic apparatus during and after acute and chronic heat stress? (3) Does the synthesis of stress proteins occur in lieu of the production or activation of photosynthetic enzymes? (4) Are any tradeoffs exacerbated when nitrogen is limiting? (5) Is there a correlation between the dynamics of stress protein production at the cellular level and whole-plant performance? (6) How are these relationships affected by plant development stage or plant genotype? The results of this work are important for a number of reasons. First, global climate models predict that the future atmosphere will have extremely high concentrations of carbon dioxide, and that the accumulation of carbon dioxide, as well as other factors, may result in temperature patterns that are subject to extreme fluctuations. Furthermore, increasing levels of carbon dioxide, in and of itself, will have substantial effects on the physiological status of plants. Understanding how the stress response of plants might be altered in a high-carbon dioxide world would therefore be an important step towards understanding how plants in both agricultural and natural settings will respond to the predicted changes in the global climate. Second, the role of stress proteins in the acquisition of stress tolerance is in the midst of an intense debate. Understanding the role that plant physiological status plays in governing the heat shock response may provide essential links to understanding when and if stress proteins function in promoting stress tolerance in plant tissues. ***