Molecular mechanisms underlying plant adaptations to extreme environments

到2050年，世界人口预计将超过90亿。由于全球农业的土地基础有限，我们在如何养活另外25亿人方面面临着巨大的不确定性。我们必须用更少的土地生产更多的粮食，但同时面临的挑战是，不可预测的、严重的不利天气、已经导致产量损失和灾难性作物歉收的情况越来越频繁。我们必须找到更有效的方法来稳定产量和确保安全的粮食供应，理想的情况是减少灌溉、化肥和作物保护化学品等昂贵的投入。然而，识别提高作物抗逆性的特征的研究几乎没有商业化的成功案例。我们通常在作物物种内或在模式植物中寻找耐性性状，这些作物或者已经通过连续的产量育种失去了耐性基因，和/或植物从一开始就没有这些耐性性状。高通量测序的出现现在使我们能够撒下更大的网来寻找耐性性状，我们的方法利用一种适应极端条件的野生作物亲戚--一种“极端植物”--来识别耐性性状及其遗传基础。 Eutrema salsugineum是一种与油菜密切相关的植物，但在高度盐碱的土壤上茁壮成长。我们发现，在加拿大育空地区发现的一种生态型对干旱表现出非凡的耐受性，它在植物基本营养磷酸盐水平较低的土壤上茁壮成长。相比之下，来自山东的生态型植物中国对干旱和低磷的耐受性要差得多。这种差异敏感性提供了一种识别对干旱和低磷耐受性与敏感性的遗传基础的方法。我们将部署一个特殊的遗传资源，其中包括180个重组自交系作图群体(RIL)，这些群体是由育空和山东鹅掌菇亲本杂交而成的。我们将结合限制性内切酶位点相关DNA测序分析、生物信息学和下游基因编辑的验证，然后进行表型分析，以确定与高效利用磷酸盐相关的基因区域，作为第一个目标，在第二个目标中，耐受水分亏缺。通常情况下，低磷植物的根较短，以便更有效地在表层土壤中寻找磷酸盐，那里的磷酸盐含量更丰富。然而，在干旱期间，需要深入土壤剖面的根才能到达后退的水分。Yukon E.salsugineum的一个有趣的特征是，对低磷的耐受性不伴随着较短的根。和世界上的许多地方一样，加拿大也面临着整个夏季更加干旱，以及全球可获得的磷矿肥料供应日益减少的未来，这两个挑战的组合已经在其自然栖息地利用我们迫切需要的农场特征成功地应对了。

The world's population is expected to exceed 9 billion by 2050. With a finite global land base for agriculture, we face huge uncertainties in how we can feed 2.5 billion more people. We must produce more food with less land but a concurrent challenge is the increasing frequency of unpredictable, severe episodes of adverse weather, conditions already leading to yield loss and catastrophic crop failures. We must find more effective ways of stabilizing yields and ensuring a secure and safe food supply, ideally involving fewer costly inputs like irrigation, fertilizers and crop protection chemicals. However, research identifying traits to improve crop stress tolerance has enjoyed few commercialization success stories. We typically source tolerance traits within crop species or in model plants that have either already lost their tolerance genes through successive breeding for yield and/or the plants never had those tolerance traits to begin with. The advent of high through-put sequencing now allows us to cast a wider net for finding tolerance traits and our approach exploits a wild crop-relative adapted to extreme conditions, an “extremophyte”, to identify tolerance traits and their genetic basis. Eutrema salsugineum is a plant that is closely related to canola but thrives on highly saline, alkaline soil. We discovered that an ecotype found in the Yukon, Canada, displays exceptional tolerance to drought and it thrives on soil that has low levels of the essential plant nutrient, phosphate. In contrast, an ecotype from Shandong, China, is far less tolerant to both drought and low phosphate. This differential sensitivity offers a means of identifying the genetic basis conferring tolerance versus sensitivity to drought and low phosphate. We will deploy an exceptional genetic resource comprising 180 recombinant inbred mapping populations (RILs) that were produced by crossing Yukon and Shandong E. salsugineum parents. We will use a combination of Restriction site Associated DNA sequencing analysis of these RILs, bioinformatics, and down-stream validation by gene editing followed by phenotypic profiling to identify regions of genes in the E. salsugineum genome associated with efficient use of phosphate as an initial objective, and in a second objective, tolerance to water deficits. Typically, plants on low phosphate have shorter roots to forage more effectively for phosphate in upper soil layers where it is more plentiful. However, roots penetrating deeply into soil profiles are needed to reach receding water during drought. An intriguing feature of Yukon E. salsugineum is that a tolerance to low phosphate is not accompanied by shorter roots. Canada, like much of the world, is facing a future of drier overall summers and dwindling global supplies of accessible rock phosphate for fertilizers, a combination of challenges that Yukon E. salsugineum already copes with successfully in its natural habitat using traits we urgently need on the farm.