Responses of Plants to Acute and Chronic Heat Stress in a High-CO2 Environment: Linking Molecular Biology with Physiological Ecology

大气中二氧化碳和其他温室气体的浓度继续上升。这一现象可能会导致全球平均气温上升，以及气温的年变化，甚至每日变化。如果植物可能比现在更频繁地暴露在突然和严重的温度上升(即热冲击)中，温度变化增加的一个后果就是。植物抵御这些高温事件的能力很可能至少部分与它们提高某些热休克蛋白(HSP)水平的能力有关。关于植物中这些蛋白质的分子生物学存在着大量的信息。然而，在施加热胁迫之前，细胞或整个植物的生理状态如何影响热休克蛋白的合成和积累或植物生存的能力，目前还知之甚少。认识上的这一空白尤其重要，因为自然环境中的植物可能不仅以温度模式的变化为特征，而且几乎肯定会含有极高水平的空气污染物(例如二氧化碳、臭氧)以及降水和土壤中不断变化的养分含量。因此，了解植物生理状态在调节热激反应中可能发挥的作用，可能会为热休克蛋白在植物组织中获得和维持耐热性方面的作用提供新的重要数据。这项研究的总体目标是评估在细胞水平上热休克蛋白的合成和积累与生长在明显不同的生理环境下的整个植物和组织的整体胁迫反应之间的关系。玉米(Zea Mays)和番茄(Lycopersica Esculentum)的特定基因型将生长在碳(CO2)和氮素有效性不同的环境中，导致植株处于不同的生理状态。然后，这些植物将暴露在热应激或控制条件下。将同时检测热激蛋白合成的动力学和正常蛋白质合成的恢复模式(分子水平)；植物获取光和二氧化碳进行光合作用的能力(组织水平)；以及整体植物表现(全株水平)。这些结果应该有助于阐明热休克蛋白的生物学作用，因为它将分子现象与发生在组织和全植物水平上的过程联系起来。此外，农业和自然系统中的植物将如何对预测的全球气候变化做出反应是一个关键问题，了解植物在高二氧化碳环境中的胁迫反应可能会如何改变，将是解决这一问题的重要一步。

Atmospheric concentrations of CO2 and other greenhouse gases continue to rise. This phenomenon 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 if that plants may be exposed to sudden and severe increases in 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 exist. Yet, little is known how the physiological state of the cell or whole-plant prior to the imposition of heat stress affect the synthesis and accumulation of hsps or the ability of plants to survive heat stress. This void in understanding is particularly critical because plants in natural environmental of plants may not only be characterized by changes in temperature patterns, but will almost certainly contain extremely high levels of air pollutants (e.g., CO2, ozone) and changing nutrient contents in precipitation and soils. Thus, understanding the role that plant physiological status may play in governing the heat shock response may provide new essential data on the roles of heat shock proteins in the acquisition and maintenance of thermotolerance in plant tissues. The overall goal of this research is to assess the relationship between the synthesis and accumulation of heat shock proteins at the cellular level and the overall stress responses of whole-plants and tissues grown under distinctly different physiological environments. Specific genotypes of corn (Zea mays) and tomato (Lycopersicon esculentum) will be grown in environments with different availabilities of carbon (CO2) and nitrogen resulting in plants at different physiological states. These plants will then be exposed to heat stress or to control conditions. The kinetics of heat shock protein synthesis and the patterns of recovery of normal protein synthesis (molecular level); the capacity of plants to harvest light and CO2 for photosynthesis (tissue level); and overall plant performance (whole-plant level), will be examined simultaneously. The results should help to clarify the biological role of hsps by linking molecular phenomena to processes occurring at tissue and whole-plant levels. Furthermore, how plants in both agricultural and natural systems will respond to the predicted changes in the global climate is a critical question, and understanding how the stress response of plants might be altered in a high CO2 environment would be an important step in solving that problem.