Molecular mechanisms underlying plant adaptations to extreme environments

到2050年，世界人口预计将超过90亿。由于全球农业用地有限，我们在如何养活25亿新增人口方面面临巨大的不确定性。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越来越频繁，这些天气已经导致产量损失和灾难性的作物歉收。我们必须找到更有效的方法来稳定产量和确保安全可靠的粮食供应，最好是减少昂贵的投入，如灌溉、化肥和作物保护化学品。然而，鉴定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式植物中寻找耐受性性状，这些植物要么已经通过连续的产量育种失去了耐受性基因，要么从一开始就没有这些耐受性性状。现在，高通量测序技术的出现使我们能够为寻找耐受性性状撒下更大的网，我们的方法利用了一种适应极端条件的野生作物亲戚，一种“极端植物”，来识别耐受性性状及其遗传基础。Eutrema salsugineum是一种与油菜密切相关的植物，但在高盐，碱性土壤中茁壮成长。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，它在土壤中生长，土壤中必需的植物养分，磷酸盐含量很低。相比之下，来自中国山东的生态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鉴定遗传基础的方法，赋予耐受性与对干旱和低磷酸盐的敏感性。本研究将利用由育空和山东沙麻亲本杂交产生的180个重组自交系作图群体（RILs）组成的特殊遗传资源。我们将使用限制性内切位点相关DNA测序分析、生物信息学和基因编辑的下游验证，然后进行表型分析，以确定salsugineum基因组中与磷酸盐有效利用相关的基因区域作为初始目标，作为第二个目标，对缺水的耐受性。通常情况下，低磷的植物根系较短，以便更有效地在磷含量更丰富的上层土壤中获取磷酸盐。然而，在干旱期间，根系需要深入土壤剖面才能到达退水处。育空E. salsugineum的一个有趣的特点是，对低磷酸盐的耐受性并不伴随着较短的根。像世界上很多地方一样，加拿大正面临着整个夏季更干燥的未来，以及全球可获得的磷矿肥料供应减少，育空E. salsugineum已经在其自然栖息地成功地应对了这些挑战，利用了我们在农场迫切需要的特性。

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.