Collaborative Research: Patterns and Mechanisms of Gene Expression in Recent Allopolyploids of Recurrent Origin

多倍体（基因组复制）是植物进化的主要力量，也是其他生物的重要进化过程，但基因组加倍的生态、生理、遗传和基因组后果尚不清楚。大多数多倍体是通过两个物种之间的杂交形成的，目前尚不清楚多倍体是否表达了双亲的所有属性，还是将每个亲本的某些特征结合在一起的马赛克。最近对多倍体基因表达的研究主要集中在拟南芥、棉花和小麦中人工产生的多倍体，而不是自然产生的多倍体。此外，尽管大多数多倍体物种在自然界中是反复形成的，但人们对这种反复形成对基因表达的影响一无所知。一个有待解决的核心问题是，不同起源的个体是否表现出相似或不同的基因表达谱。为研究天然种群近期多倍体和复发多倍体提供了一个模型系统。20世纪初，随着三种二倍体物种（T. dubius、T. pratensis和T. porrifolius）从欧洲传入北美西部，形成了两个新的多倍体物种（T. mirus和T. miscellus）。混合角象特别有趣，因为它也是相互形成的（即一次以可疑角象为母本，多次以pratensis为母本）。该项目将涉及分子和基因组方法来解决一系列问题，这些问题对增加对多倍体的理解至关重要。例如，在这些新近形成的多倍体中是否会出现新的基因表达？基因表达模式在独立起源的多倍体群体中不同吗？基因表达是否受到父母贡献的影响？F1杂交种和新产生的多倍体的基因表达模式与自然产生的多倍体不同吗？什么类型的基因在天然多倍体中经历差异表达，什么类型的机制导致观察到的基因表达差异？这些问题在目前的作物系统或再合成多倍体中无法轻易解决。这项研究将首次对自然多倍体种群的基因表达进行严格的评估，并为两种新的多倍体物种的快速进化成功提供新的见解。此次合作由p.d. Soltis, p.s oltis， J. Tate（佛罗里达大学）和zz . J. Chen（德州农机大学）组成，他们将各自在进化生物学和分子遗传学方面的专业知识结合在一起。培养本科生和研究生、博士后和K-12教师的机会被纳入该项目。

Polyploidy (genome duplication) represents a major force in plant evolution and an important evolutionary process in other organisms, but the ecological, physiological, genetic, and genomic consequences of genome doubling remain mostly unknown. Most polyploids are formed via hybridization between two species, and it is unclear whether the polyploids express all of the attributes of both parents or are mosaics that combine some characters of each parent. Recent studies of polyploid gene expression have focused on artificially produced polyploids in Arabidopsis, cotton, and wheat rather than on naturally occurring polyploids. In addition, although most polyploid species have formed repeatedly in nature, nothing is known about the consequences of this recurrent formation on gene expression. A central question yet to be addressed is whether individuals of separate origin show similar or divergent gene expression profiles. A model system for the study of recent and recurrent polyploidy in natural populations is provided by Tragopogon (Asteraceae, the Sunflower family). Two new polyploid species (T. mirus and T. miscellus) were formed following the introduction of three diploid species (T. dubius, T. pratensis, and T. porrifolius) from Europe to western North America during the early 1900s. Tragopogon miscellus is particularly interesting because it has also formed reciprocally (that is, once with T. dubius as the maternal parent and multiple times with T. pratensis as the maternal parent). This project will involve molecular and genomic approaches to address a series of questions that are fundamental to an increased understanding of polyploidy. For example, does novel gene expression occur in these recently formed polyploids? Do gene expression patterns differ among polyploid populations of independent origin? Is gene expression affected by maternal and paternal contributions? Do gene expression patterns in F1 hybrids and newly produced polyploids differ from those of the naturally occurring polyploids? What types of genes undergo differential expression in the natural polyploids, and what types of mechanisms lead to the observed differences in gene expression? Such questions cannot be readily addressed in current crop systems or with resynthesized polyploids. This research will provide the first rigorous assessment of gene expression in natural polyploid populations, plus new insights into the rapid evolutionary success of two new polyploid species. The collaboration among PIs D. Soltis, P. Soltis, J. Tate (University of Florida) and Z. J. Chen (Texas A&M University) combines their respective expertise in evolutionary biology and molecular genetics. Opportunities for training of undergraduate and graduate students, post-docs, and K-12 teachers are integrated into the project.