FOR 496: Poplar - a model to address tree-specific questions

德国杨树研究小组的主要目标是解决有关树木营养和适应环境压力的具体问题。此外，还可以分析这两个因素之间潜在的相互作用。-树木营养方面的具体问题：在森林生态系统中，氮的可用性限制了树木的生长，与一年生草本植物拟南芥的模式植物相反，树木的氮获取受到与菌根真菌的共生相互作用的强烈影响。此外，由于养分需求的季节性波动和暴露于不断变化的环境胁迫，树木对氮营养的调节更为复杂。采用生态生理、生物化学和分子生物学相结合的方法研究根系对氮的吸收调控。这些数据将被用来建立一个整个植物氮通量的模型。为了实现这一目标，氮转运的机制，转运系统和酶的组织特异性表达和调控将被分析。除氮外，磷和钾对生长和木材形成也很重要。通过使用解剖学、电生理学和分子技术以及采用显微解剖，将解决大量营养素的供应在多大程度上影响木材形成的问题。——适应环境压力。盐度是当今世界面临的一个重大问题。在杨树属中，胡杨的耐盐性是突出的。因此，这棵模型树为德国杨树研究小组研究结构、生理和分子适应压力提供了完美的先决条件。研究了胡杨耐盐性的生理和分子基础。通过微阵列分析，将确定与应激诱导变化相关的新的候选基因。与草本植物相比，杨树释放出大量的异戊二烯。异戊二烯在树木中大量产生的一个潜在功能是提高耐温性。将研究异戊二烯生物合成途径过表达基因的转基因杨树的耐热性。这些结果可以用来获得能够更好地抵御盐胁迫和延长热期的树木，并在胁迫条件下表现出更好的生长。

The main aim of the Poplar Research Group Germany is to address tree-specific questions with respect to nutrition and adaptation to environmental stresses. Furthermore it is possible to analyse potential interactions between both factors. -- Tree specific questions in respect of nutrition:In forest ecosystems the availability of nitrogen limits the growth of trees and its acquisition in trees is - in contrast to the model plant for annual herbs Arabidopsis - strongly affected by symbiotic interactions with mycorrhizal fungi. Furthermore, regulation of nitrogen nutrition in trees is more complex because of seasonally fluctuating nutrient demand and exposure to changing environmental stresses. By combination of ecophysiological, biochemical and molecular methods the regulation of nitrogen uptake into roots will be studied. These data will be used to create a model of a whole-plant-N-flux. Towards this goal the mechanism of nitrogen transport, the tissue-specific expression and regulation of transport systems and enzymes will be analysed. In addition to nitrogen, phosphorus and potassium are important for growth and wood formation. By use of anatomical, electrophysiological and molecular techniques and by employing microdissection the question will be addressed to which extent the supply with macronutrients influences wood formation. -- Adaptation to environmental stresses:Salinity is a major problem in the world. In the genus Populus, Populus euphratica is outstanding with respect to its salt tolerance. Therefore this model tree offers perfect prerequisites for the Poplar Research Group Germany to study structural, physiological and molecular adaptations to stress. The physiological and molecular basis for salt tolerance will be identified in Populus euphratica. By microarray analyses new candidate genes related to stress-induced changes will be identified. In contrast to herbs poplar trees emit high amounts of isoprene. One potential function of the strong isoprene production in trees is to increase temperature tolerance. Transgenic poplars overexpressing genes of the isoprene biosynthesis pathway will be investigated for thermotolerance. These results can be utilised to obtain trees which are better capable of surviving salt stress and extended heat periods and show better growth under stress conditions.