EAGER: Allopolyploidy and photosynthesis: a whole-transcriptome approach

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Allopolyploidy (whole genome duplication following hybridization) is an important speciation mechanism in flowering plants; many crop species, including soybean (Glycine max), are polyploids. Allopolyploidy is known to lead to structural and regulatory changes that can result in morphological, physiological, and ecological novelty. There is considerable interest in ascertaining whether there are emergent properties ('rules') that could be responsible for the apparent success of so many allopolyploids. Glycine is an excellent model for addressing this question; among its approximately 30 species is a group of eight recently formed allotetraploid species uniting genomes from eight diploid progenitors in various combinations. Unlike any of the diploids, which are all confined to Australia, five of the eight allopolyploids have colonized islands of the Pacific Ocean, suggesting that they have a greater ecological breadth than their progenitors. Photoprotection - a set of mechanisms for dissipating potentially damaging excess light energy - is an adaptively important physiological process that could contribute to the success of Glycine allopolyploids. We are using a "next generation," high-throughput sequencing method (Illumina) to obtain a deep and detailed profile of gene expression in three Glycine allopolyploid species and their diploid progenitors under normal light and high light stress conditions to assess which genes are involved in photoprotection, how they are regulated in diploids and polyploids, what the contribution of the two diploid progenitor genomes is at each of thousands of expressed genes in each polyploid, and whether there are shared patterns of gene expression in independently formed allopolyploids that could constitute predictable 'rules' governing photoprotection in polyploid species of Glycine and other flowering plants. Broader impacts include deepening our understanding of polyploidy, a process that has shaped the genomes of many agriculturally important plant species; the project will also support training of a graduate student.