DISSERTATION RESEARCH: Genome Evolution of a Polyploid Complex in Sorghum (Poaceae)

非技术性摘要当今系统学中最具挑战性的问题之一是了解密切相关物种之间的关系，特别是那些经历了杂交和多倍体等过程的物种，即生物体基因组加倍。 本研究探讨了这些过程对禾本科高粱组种间关系的影响。 高粱组包括栽培高粱[Sorcerium bicolor（L.）Moench]和约翰逊草（Johnsongrass）[Sorghalepense（L.）.]，世界上最毒的杂草之一 S. halepense是一个多倍体，被认为是来自S.双色的。 S. bicolor和S. Halepense不是遗传隔离的，可能会杂交，产生复杂的关系模式。 来自该物种复合体个体的植物核和叶绿体基因组多个部分的DNA序列数据将用于重建进化关系。 这些关系可以被检查的模式，这可能与地理，植物外观，入侵，或其他factors.In光的经济重要性，这一物种复杂的Sorcerium，更好地了解它们的关系是必不可少的。栽培高粱是世界上第五大谷类作物，也是半干旱热带地区的主要谷物。相对于玉米，它具有较小的基因组大小，使其成为禾本科比较基因组学研究的理想模式生物。S.假俭草是世界上十种最有害的杂草之一。 入侵物种仅次于栖息地破坏，是全球生物多样性的第二大威胁，每年造成作物减产数十亿美元。 这项研究也将有助于更好地了解多倍体的过程及其对植物进化的影响。 多倍体的过程与广泛的基因组变化有关。 目前的估计表明，至少有50-70%的被子植物在其进化史上的某个时刻经历了基因组复制，使多倍性成为植物进化中的一个重要因素。 多倍性也塑造了许多其他生物体的基因组，如脊椎动物，包括人类，并在某些癌症中发挥作用。 多倍体和杂交都有可能增加物种内的遗传变异性，并可能增加入侵能力。 更好地了解这些过程及其对这些经济上重要的物种的进化的影响，可能有利于各种领域，包括植物育种和杂草控制工作。

NSF DDIG Non-technical AbstractOne of the most challenging problems in systematics today is understanding the relationships between closely related species, especially those that have been subject to processes such as hybridization and polyploidy, the doubling of an organism's genome. This research investigates the effects of these processes on the relationships among species of Sorghum sect. Sorghum (Poaceae). Sorghum sect. Sorghum includes cultivated sorghum [Sorghum bicolor (L.) Moench] and johnsongrass [Sorghum halepense (L.) Pers.], one of the world's most noxious weeds. S. halepense is a polyploid, thought to be derived from S. bicolor. S. bicolor and S. halepense are not genetically isolated and may hybridize, creating complex patterns of relationship. DNA sequence data for multiple sections of the plants' nuclear and chloroplast genomes from individuals of this species complex will be used to reconstruct evolutionary relationships. These relationships can be examined for the presence of patterns, which may be correlated with geography, plant appearance, invasiveness, or other factors.In light of the economic importance of this species complex in Sorghum, a better understanding of their relationships is essential. Cultivated sorghum is the fifth most important cereal crop in the world and a staple grain in the semi-arid tropics. It has a small genome size relative to that of maize, making it an ideal model organism for comparative genomics studies in the grasses. S. halepense is one of the ten most noxious weeds worldwide. Invasive species rank second behind only habitat destruction as the largest threat to biodiversity worldwide and cost billions of dollars each year in reductions in crop yields. This research also will contribute to a greater understanding of the process of polyploidy and its impact on plant evolution. The process of polyploidy has been linked to extensive genomic changes. Current estimates suggest that at least 50-70% of angiosperms have undergone genome duplication at some point in their evolutionary past, making polyploidy a significant factor in plant evolution. Polyploidy has also shaped the genomes of many other organisms, such as vertebrates, including humans, and plays a role in some cancers. Polyploidy and hybridization both have the potential to increase genetic variability within a species, and possibly invasive ability. A greater understanding of these processes and their effects on the evolution of these economically important species may be beneficial to a variety of fields, including plant breeding and weed control efforts.