TRANSCRIPTIONAL REGULATION OF RESILIENCE TO PHOTO-INHIBITION UNDER CHILLING CONDITIONS IN MAIZE.

未来几十年，全球粮食需求预计将大幅增长，预计到2050年，人口将从目前的75亿增加到100亿，并显著转向越来越高热量的饮食。与此同时，几种主要粮食作物通过传统育种提高生产率的速度已经放缓，全球气候变化正在给粮食生产带来额外压力，特别是通过极端天气事件。如果人类要成功地避免未来的全球粮食危机，迫切需要投资于每单位土地面积可持续和有弹性的作物生产力。C4作物玉米(玉米)目前是全球主导作物，全球产量为10.9亿吨。具有C4光合作用途径的作物物种通过将二氧化碳集中在其中心酶Rubisco周围，绕过了Calvin-Benson-Bassham循环的一些低效。C4物种的生理优势，如光合作用、水分和氮素的高效利用，使其中几个物种成为与农业相关的作物或杂草，并主导了地球上较温暖地区的许多开阔景观生物群。它们也构成了试图通过安装C4生物化学和解剖学来提高C3作物(如水稻)生产力的理论基础。然而，起源于热带和亚热带的作物通常对低温敏感，特别是与光暴露相结合，这会引起低温诱导的光抑制，即植物不能进行光合作用的较长时间，并且对吸收的太阳光非常敏感。大约9000年前，墨西哥的古代农民驯化了玉米，在温带地区种植的作物中，玉米是最容易受到冷害光抑制的作物之一。因此，高纬度地区的玉米产量受到相对较短的生长季的限制，而且玉米对由于早季和晚季寒流以及早季建立足够的叶面积以有效捕捉光线并与杂草竞争而造成的产量损失很敏感。提高玉米的耐冷性将通过增加玉米的纬度范围和帮助降低年产量变异性而产生强大的经济影响。长期以来，人们已经知道不同的玉米材料之间存在着相当大的耐冷性和光抑制敏感性的差异，这通常反映了品种发展地区的气候，例如来自美国玉米带的凹陷品种与更温和地区如西北欧、加拿大或阿根廷开发的打火石品种之间的差异，但这种差异的机制和遗传基础在很大程度上仍不清楚。本项目的中心目的是提高对冷害光抑制敏感性的遗传差异的理解，以帮助在温带地区开发优良的玉米种质资源。本项目将利用一个具有结构性遗传变异的新玉米群体来鉴定与冷害光抑制有关的性状差异，这些差异与遗传变异有关。同样，基因表达水平的变化将被测量并与特定基因组位置的序列变化相关联。利用这些在田间和受控环境条件下的平行实验方法，该项目将确定在低温和高光反应中控制基因表达的特定基因，并精确定位玉米中哪些基因组位置显示出与这些控制基因的表达相关的变异。该项目的成果将增加用于培育耐寒性状的遗传标记的可用性，并增强对基因表达反应在提高玉米耐冷性方面的作用的理解。

Global food demand is expected to increase substantially over the coming decades, with a predicted increase in human population from 7.5 billion currently to 10 billion by 2050 and significant shifts to increasingly calorie-rich diets. This comes at a time when productivity increases of several major food crops through conventional breeding have slowed down and global climate change is putting additional pressures on food production, especially via extreme weather events. Investing in sustainable and resilient crop productivity per unit land area is urgently needed, if humanity is to successfully avert future global food crises.The C4 crop Zea mays (maize) is currently the dominant global crop with a world-wide production volume of 1.09 billion metric tons. Crop species with the C4 photosynthetic pathway circumvent some of the inefficiencies of the Calvin-Benson-Bassham cycle by concentrating carbon dioxide around its central enzyme Rubisco. The physiological advantages of C4 species, such as high efficiency of photosynthetic light, water and nitrogen use, have allowed several of these species to become agriculturally relevant crops or weeds, and to dominate many of the open landscape biomes across warmer regions of the earth. They also form the rationale for attempts to improve productivity of C3 crops such as rice, by installing C4 biochemistry and anatomy.However, crops originating from the tropics and sub-tropics are often sensitive to chilling temperatures, in particular in combination with exposure to light which gives rise to chilling-induced photoinhibition, i.e. prolonged periods where plants are incapable of doing photosynthesis and are very sensitive to damage by absorbed sunlight. Maize was domesticated by ancient farmers in Mexico approximately 9000 years ago and is one of the most susceptible crops to chilling-induced photoinhibition amongst those grown in temperate regions. As a result, maize yields at higher latitudes are limited by a relatively short growing season and maize is sensitive to yield losses due to early and late season cold snaps and poor early season establishment of sufficient leaf area to efficiently capture light and compete with weeds.Improving chilling tolerance in maize will have strong economic impact by increasing the latitudinal range of maize and by helping to reduce year by year yield variability. It has been known for a long time that considerable variability in chilling tolerance and photoinhibition sensitivity exists amongst different maize accessions, often reflecting the climate at the region of cultivar development, such as between dent varieties from the US corn belt and flint varieties developed in more temperate regions like Northwest Europe, Canada or Argentina, but the mechanistic and genetic basis of this variation still remains largely undefined. The central aim of this project is to improve understanding of genetic differences in sensitivity to chilling-induced photoinhibition to aid development of superior maize germplasm for temperate regions.This project will use a novel maize population with structured genetic variation to identify differences in traits involved in chilling-induced photoinhibition that are statistically correlated to genetic variation. Similarly, variation in gene expression levels will be measured and correlated to sequence variation at specific genomic locations. Using these parallel experimental approaches under field and controlled environment conditions, the project will identify specific genes that are central in controlling gene expression in response to chilling and high light, as well as pinpoint which genomic locations in maize show variation that correlates with the expression of these control genes. The projects outcomes will increase availability of genetic markers for breeding of chilling-tolerant traits, as well as enhance understanding of the role of gene expression responses in improving chilling-tolerance in maize.