Tracking the altitudinal adaptation of Andean maize using archaeogenomics

在我们考虑新的农业环境以满足我们的粮食安全需求时，了解作物如何适应较低的水供应、较低的温度和较短的生长季条件是很重要的。这种适应在过去也发生过，特别是对高海拔的适应。玉米从海平面低地适应到海拔4000米以上的安第斯山脉高地，是所有作物中最极端的海拔适应之一，记录在跨越过去2600年的一系列玉米考古样本中，因为一系列复杂的安第斯文化扩展到了山脉。关于这些文化是如何相互作用的，以及玉米是如何在相对较短的时间内实现如此极端的适应，人们仍然不太清楚。近年来，我们发现玉米不是一次而是多次地从其teosinte祖先向外扩展，每一波都携带不同的遗传多样性成分，这些成分可能具有不同的适应潜力。特别是，后来的玉米扩张浪潮携带了第二个野生祖先物种teosinte的遗传多样性，该物种适应了中美洲高原。我们不知道后一波浪潮在多大程度上导致玉米进化到高海拔，也不知道高海拔适应是否已经通过当地的新适应实现了。我们也不知道这种玉米是如何在不同的文化领域进行交换的。为了梳理出这些因素，理想的做法是检查当时玉米的基因组，以确定它们适应的性质和它们的祖先，以及它们何时发生变化。考古基因组学技术的现状是这样的，从考古材料中提取基因组已成为主流，并可以大规模进行。我们有一个独特的277个考古玉米样本，涵盖了玉米从略高于海平面到4000米以上的扩张--比目前已知的任何玉米都要高。在这个项目中，我们将从安第斯地区的10个培养物中回收至少150个古基因组，以追踪玉米对高海拔的适应情况。通过这种方式，我们将能够回答上面的问题，即玉米如何适应，是否以及如何在不同文化之间进行交换，以及过去的玉米是否具有意味着它可以比今天的玉米生长得更高的特性。总而言之，这些发现对于理解安第斯考古学、玉米生物学和进化研究以及未来玉米育种的潜在产出都将是重要的。

Understanding how crops can adapt to conditions of lower water availability, lower temperatures and shorter growing seasons is of importance as we consider new environments for agriculture to meet our food security needs. Such adaptations have occurred in the past, in particular adaptations to high altitude. The adaptation of maize from the sea level lowlands to the heights of the Andes at over 4000 metres above sea level represents one of the most extreme altitudinal adaptations of any crop and is recorded in a series of archaeological samples of maize over time spanning the last 2600 years as a complex series of Andean cultures expanded into the mountain chain. Much is still not understood about how these cultures may have interacted, and how maize achieved such an extreme adaptation in a relatively short period of time. In recent years we have discovered that maize expanded out of its area of origin from its teosinte progenitor not once but on multiple occasions, each wave carrying different compositions of genetic diversity that may have had different adaptive potential. In particular, later waves of maize expansion carried genetic diversity from a second wild progenitor species of teosinte that was adapted to the highlands of Mesoamerica. We do not know to what extent this later wave was responsible for maize's progression to high altitude or whether high altitude adaptations had already been achieved through novel adaptations locally. Nor do we know how such maize might have been exchanged throughout the different cultural spheres. To tease apart these factors it would be ideal to examine the genomes of the maize of that time to identify the nature of their adaptations and their ancestry and when they changed.The state of archaeogenomics technology is such now that recovery of genomes from archaeological materials has become mainstream and can be carried out at scale. We have a unique collection of 277 archaeological maize samples that cover the expansion of maize from just above sea level to over 4000 metres - higher than any maize is known to grow today. In this project we will recover at least 150 archaeogenomes from across 10 cultures in the Andean area to track the adaptation of maize to high altitude. In this way we will be able to answer the questions above about how maize adapted, if and how it was exchanged between cultures, and whether the maize of the past had properties that meant that it could grow higher than maize today. Together these findings will be important for understanding Andean archaeology, maize biology and evolutionary studies in general with potential outputs for maize breeding in the future.