Map-Based Dissection of Sorghum Drought Tolerance Gene Networks

谷物提供了世界上70%的卡路里，而水是世界范围内粮食生产最有限的自然资源。高粱，一种起源于非洲的草，是世界上第五大谷物。高粱已经进化出了一些特性，可以在炎热干燥的环境中生产粮食（即，厚的叶蜡，深的根系），并在水分有限的情况下促进持续生长。高粱的基因序列也与水稻、玉米和小麦等其他重要谷物相似，而且基因组相对较小（仅为水稻的两倍，比小麦小20倍）。一些高粱基因型表现出明显的耐旱性。特别有趣的是，植物在经历水分限制时仍能继续生长，从而表现出“保持绿色”表型。基因组学方法将使科学家能够了解构成保持绿色性状基础的基因网络。为了实现这一目标，将进一步开发高粱的基因组资源。已经建立的TAMU-ARS高粱遗传和物理图谱将进一步开发，并将与水稻基因组序列对齐。对高粱染色体进行鉴定，建立病毒诱导基因沉默系统（VIGS/RNAi）。育种者正在开发能够精确定位耐旱基因的遗传群体，这对候选基因的鉴定至关重要。所有这些遗传工具将用于精细定位，分离和表征控制高粱保持绿色性状表达的基因网络，这是在缺水环境下粮食生产的核心。信息将通过科学和大众出版物、在会议上的发言、与开发国家牧草关系数据库Gramene的小组合作（http://www.gramene.org）以及在当地项目网站（http://SorghumGenome.tamu.edu）上公开提供。几个高粱BAC的完整序列、BAC序列等序列数据将提交给GenBank， DNA序列数据将提供给Gramene的策展人。所产生的信息和技术将帮助公共和私人谷物育种者提高美国作物的抗旱性和生产力，并将促进“保持绿色”性状转移到其他缺乏高粱抗旱性的谷物品种上。

Cereals provide seventy percent of the world's calories and water is the most limiting natural resource for grain production worldwide. Sorghum, a grass with its origin in Africa, is the fifth most important cereal worldwide. Sorghum has evolved characteristics that permit grain production in hot dry environments (i.e., thick leaf wax, deep root system) and that facilitate continued growth when water availability is limited. Sorghum is also similar in gene sequence to other important cereals such as rice, corn, and wheat and has a relatively small genome (only twice the size of rice and 20-fold smaller than wheat). Some sorghum genotypes show distinct drought-tolerance. Of particular interest are plants that continue to grow when experiencing water limitation, thus showing a 'stay-green' phenotype. A genomics approach will allow scientists to understand the network of genes that form the basis to stay green traits. To accomplish this, genomic resources will be further developed in Sorghum. The TAMU-ARS sorghum genetic and physical map, already established, will be further developed and will be aligned to the rice genome sequence. Sorghum chromosomes will be characterized and a virus-induced gene silencing system (VIGS/RNAi) will be established. Breeders are developing the genetic populations that permit precise chromosomal localization of drought tolerance genes, which is essential for candidate gene identification. All these genetic tools will be used to fine map, isolate, and characterize this network of genes that control expression of the sorghum stay-green trait that is central to grain production in water limited environments.Information will be made publicly available through scientific and popular publications, presentations at meetings, and through collaboration with the groups developing Gramene, a national relational database for grasses (http://www.gramene.org) and on a local project web site (http://SorghumGenome.tamu.edu). The complete sequence of several sorghum BACs, BAC sequence and other sequence data will be submitted to GenBank and DNA sequence data will be provided to the curators of Gramene. The information and technology generated will help public and private cereal breeders to improve US crop drought tolerance and productivity and will facilitate the transfer of the 'stay green' trait to other cereal species that lack sorghum's tolerance to drought.