Plant tolerance to abiotic stress: Physiological and metabolic mechanisms

我们研究了一种耐逆性很强的原生植物--沙棘。在加拿大，在育空和穿过草原到安大略省西部的碱性盐碱地上发现了Eutrema。正如它的分布和土壤偏好所暗示的那样，它具有非凡的天生能力，可以在水分有限、养分不足的寒冷地区生长。Eutrema是研究抗逆性特征的一个很好的模式，因为它与加拿大珍贵的油料作物油菜籽有着密切的亲缘关系。在过去的四年里，出现了许多遗传和基因组资源，以促进对这种植物的研究，我领导的Eutrema基因组学小组为这些进展做出了巨大贡献。有了完全测序的基因组和转录本，我们可以很好地研究这种植物抵御不利条件的特殊能力背后的机制，以期在胁迫敏感的作物(包括油菜)中增强这些特性。*耐旱和耐盐植物合成并积累非扰动的有机溶质，使它们能够建立浓度梯度，推动水分进入根。利用生理学和代谢组学的方法，我们报道了Eutrema在胁迫下产生的溶质显示出可塑性。在育空地区的高盐碱地，氮素含量低，Eutrema积累碳水化合物以进行渗透调节，而在我们的橱柜里，盐胁迫下的植物定期施肥，它们积累氨基酸脯氨酸。值得注意的是，盐胁迫下的橱柜植物提供的氮素很少，但充足的氮素水平与提供充足氮素的胁迫植物在视觉上难以区分。正常情况下，氮素缺乏会导致植株严重发育迟缓。通过我们最近的转录组工作，我们发现育空地区的Eutrema生态型在我们的橱柜中生长时实际上是缺硫的，尽管它们定期受精，而且看起来并不缺硫。硫是一种营养物质，在植物对胁迫的反应中也扮演着重要的角色，特别是在抑制活性氧产生的损害方面。在磷的情况下，Eutrema可以非常节俭，植物在低磷含量的介质中生长得很好，就像它们在这种养分的无限供应中所做的那样，即使在有盐的情况下也是如此。很明显，我们可以从Eutrema如何管理低养分可获得性中学到很多东西，特别是在压力下。我们的研究目标集中在探索这种植物管理非生物胁迫的特殊能力背后的机制，特别是在有限的营养条件下。作物的高养分利用效率对变化的天气模式更有弹性，是可持续作物生产的理想特征组合，特别是在全球气候变化的全面影响显现的情况下。

We study a highly stress tolerant native plant, Eutrema salsugineum. In Canada, Eutrema is found on alkaline, saline soils in the Yukon and across the Prairies to western Ontario. As its distribution and soil preference implies, it has an extraordinary innate capacity to grow in cold areas where water is limiting and nutrients are low. Eutrema is an excellent model to study stress tolerance traits because of its close phylogenetic relationship to canola, Canada's valuable oilseed crop. In the past four years many genetic and genomic resources have emerged to facilitate research on this plant and the Eutrema genomics group that I lead has made strong contributions to these advances. With fully sequenced genomes and transcriptomes available, we are in an excellent position to investigate the mechanisms underlying the exceptional capacity of this plant to withstand adverse conditions with a view to enhancing these traits in stress sensitive crops, including canola.****     Drought and salt tolerant plants synthesize and accumulate non-perturbing organic solutes that enable them to establish a concentration gradient to drive water movement into the roots. Using physiology and metabolomics approaches, we reported that Eutrema shows plasticity with respect to the solutes they produce under stress. In the highly saline fields of the Yukon where nitrogen is low, Eutrema accumulates carbohydrates for osmotic adjustment and in our cabinets where salt-stressed plants are fertilized regularly, they accumulate the amino acid proline. Remarkably, salt-stressed cabinet plants provided low, but sufficient levels of nitrogen were visually indistinguishable from stressed plants given ample nitrogen. Normally a deficiency in nitrogen produces a severely stunted plant. Through our more recent transcriptome work we discovered that the Eutrema ecotype from the Yukon is actually sulfur deficient when grown in our cabinets although they are fertilized regularly and they do not look like they lack sulfur. Sulfur is a nutrient that also figures prominently in how plants respond to stress, particularly in suppressing the damage produced by reactive oxygen species. In the case of phosphorous, Eutrema can be extremely frugal and plants grow as well in a medium with a low content of phosphate as they do with a non-limiting supply of this nutrient, even in the presence of salt. It is clear that we have much to learn from how Eutrema manages low nutrient availability, particularly under stress. Our research objectives are focused on exploring mechanisms underlying the exceptional capacity for this plant to manage abiotic stresses, particularly under limiting nutrient conditions. High nutrient use efficiencies in crops that are more resilient against fluctuating weather patterns is an ideal combination of traits for sustainable crop production, particularly as the full impact of global climate change unfolds.*********