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

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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.