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加，预计到2050年，全球人口将从目前的75亿增加到100亿，人们的饮食将显著转向越来越高热量的饮食。目前，几种主要粮食作物通过常规育种提高产量的速度已经放缓，全球气候变化正给粮食生产带来额外压力，尤其是极端天气事件。如果人类要成功避免未来的全球粮食危机，就迫切需要投资于单位土地面积的可持续和弹性作物生产力。C4作物Zea mays（玉米）目前是全球主要作物，全球产量为10.9亿吨。具有C4光合途径的作物通过将二氧化碳集中在其中心酶Rubisco周围，规避了卡尔文-本森-巴萨姆循环的一些低效率。C4物种的生理优势，如光合作用、水和氮的高效利用，使其中一些物种成为农业相关的作物或杂草，并在地球温暖地区的许多开放景观生物群系中占据主导地位。它们也构成了试图通过安装C4生物化学和解剖装置来提高C3作物（如水稻）产量的基本原理。然而，原产于热带和亚热带的作物往往对低温敏感，特别是在暴露于光的情况下，会产生寒流诱导的光抑制，即植物不能进行光合作用的时间延长，对吸收的阳光的损害非常敏感。玉米大约在9000年前由墨西哥的古代农民驯化，是温带地区种植的最易受寒冷诱导光抑制的作物之一。因此，高纬度地区的玉米产量受到相对较短的生长季节的限制，玉米对由于早、晚季节寒流和早期建立足够的叶面积以有效地捕获光和与杂草竞争而造成的产量损失很敏感。提高玉米的抗寒性将通过增加玉米的纬度范围和帮助减少逐年产量变异而产生强烈的经济影响。长期以来，人们已经知道不同的玉米品种在抗寒性和光抑制敏感性方面存在相当大的差异，这通常反映了品种发育地区的气候，例如美国玉米带的凹痕品种与西北欧、加拿大或阿根廷等温带地区开发的燧石品种之间的差异，但这种差异的机制和遗传基础仍未明确。本项目的中心目的是提高对低温光抑制敏感性遗传差异的理解，以帮助开发温带地区的优质玉米种质。该项目将使用一个具有结构遗传变异的新型玉米群体来确定与冷致光抑制有关的性状差异，这些性状与遗传变异有统计学上的相关性。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，该项目将确定在寒冷和强光条件下控制基因表达的特定基因，并查明玉米中哪些基因组位置显示出与这些控制基因表达相关的变异。该项目的成果将增加耐冷性状遗传标记的可获得性，并加深对基因表达响应在提高玉米耐冷性中的作用的认识。

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.