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恶劣天气事件越来越频繁，这些条件已经导致产量损失和灾难性的农作物歉收。我们必须找到更有效的方法来稳定产量并确保粮食供应安全，最好减少灌溉、化肥和作物保护化学品等昂贵投入。然而，识别提高作物抗逆性性状的研究很少有商业化的成功案例。我们通常在作物物种或模型植物中寻找耐受性状，这些作物物种或模型植物要么通过连续的产量育种而失去了耐受性基因，和/或植物从一开始就从未具有这些耐受性状。高通量测序的出现使我们能够撒下更广泛的网来寻找耐受性状，我们的方法利用适应极端条件的野生作物相关物（一种“极端植物”）来识别耐受性状及其遗传基础。 Eutrema salsugineum 是一种与油菜籽密切相关的植物，但在高盐度、碱性土壤中生长茂盛。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，并且在植物必需营养素磷酸盐含量较低的土壤中茁壮成长。相比之下，中国山东的一种生态类型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遗传基础的方法，该遗传基础赋予对干旱和低磷酸盐的耐受性与敏感性。我们将部署一个特殊的遗传资源，其中包括 180 个重组近交作图群体 (RIL)，这些群体是通过育空地区和山东 E. salsugineum 亲本杂交产生的。我们将结合使用这些 RIL 的限制性位点相关 DNA 测序分析、生物信息学和通过基因编辑进行的下游验证，然后进行表型分析，以识别 E. salsugineum 基因组中与有效利用磷酸盐相关的基因区域作为初始目标，第二个目标是对缺水的耐受性。 通常，低磷酸盐植物的根较短，可以更有效地在上层土壤中更有效地获取磷酸盐，那里的磷酸盐更丰富。然而，在干旱期间，需要根部深入土壤剖面才能到达退缩的水。育空 E. salsugineum 的一个有趣特征是，对低磷酸盐的耐受性并不伴随着较短的根。与世界大部分地区一样，加拿大未来将面临夏季整体干燥和全球肥料用磷矿供应量减少的局面，育空盐沼已经利用我们农场迫切需要的特性在其自然栖息地成功应对了这些挑战。

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.