Untangling the molecular mechanisms underlying adaptive difference between autopolyploid and its diploid ancestor: A case study of Hordeum bulbosum species

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Polyploidization has been proposed as a major force for speciation and genome evolution. Despite enormous research progress, many basic questions concerning the genetic consequences of polyploid evolution remain unanswered, specifically molecular mechanisms that might promote speciation after whole-genome duplication, especially in ecology, physiology, and evolution.Molecular studies of allopolyploids have revealed structural and functional changes caused by polyploidization as the key to the success of polyploids, which might be induced by either hybridization or genome doubling or a combination of both. The effect of genome doubling can only be examined using diploids and autopolyploids. Previous studies suggested that genome doubling has a greater influence on stress tolerance than hybridization. Some studies on synthetic autopolyploids showed that an autopolyploid has a stronger stress tolerance than its diploid. However, we still lack evidence that observed transcriptional and genomic changes actually lead to greater adaptation of autopolyploids, in natural populations. MicroRNAs not only play an important role in regulating gene expression during genome doubling but also in various stresses response, resulting in allopolyploids that adapt to different environmental conditions. However, how miRNAs in autopolyploids respond relative to its diploid to environmental changes has rarely been studied. Although limited or no changes on genome reorganization and structure were reported in synthetic autopolyploids, methylation changes in these polyploids occurred, which may contribute to ecological and physiological novelty. However, changes to methylation patterns do not always accompany genome doubling. It is unclear why the effect was observed in particular plant systems but not in others.Hordeum bulbosum has both diploid and autotetraploid cytotypes, and is an excellent model system for autoployploidy studies. We will use innovative molecular and experimental approaches to test the hypothesis that natural autotetraploids have experienced major genetic and epigenetic changes to promote evolution via increased adaptability. Specific objectives are: 1) to reveal the molecular basis to explain the adaptive difference between diploid and autopolyploid at the transcriptome, proteome, and miRNA levels; 2) to determine if methylation changes induced by genome doubling per se promote autopolyploid adaption, and if these are linked to different ecotypes; 3) to train students in novel interdisciplinarity both in molecular biology and evolution. The outcome of this study will reveal the adaptive role of polyploidy in response to environmental changes, will provide novel knowledge on the role of polyploidy per se on speciation, and will be of both practical and theoretical interest since the generated knowledge can be used in polyploidy breeding.