Gene expression in a wild autopolyploid sunflower series.

Polyploidy, or genome doubling, is a common mechanism in the evolution of plants. This genome duplication can rapidly lead to genomic changes between ploidy levels. In particular, allopolyploids that result from interspecific hybridization can show a large number of changes in gene expression immediately after the polyploidy event. These are likely due to epigenetic changes that do not alter the underlying DNA sequence. This may be due in part to the hybrid origin of these allopolyploids. In autopolyploids, a small number of studies have shown that there may also be some gene expression changes between ploidy levels, albeit to a much smaller degree. However, these studies have focused on inbred lines of single populations. This study examines silencing and/or novel gene expression in diploid, autotetraploid, and autohexaploid lineages of Helianthus decapetalus. Using cDNA-amplified fragment length polymorphism, we examined gene expression in 5 populations of these lineages. The results show no ploidy level-specific differences in gene silencing or novel gene expression. All gene expression differences are among populations and may be due to independent evolutionary origins. These results support the conclusions of previous studies that gene expression differences among allopolyploids are likely due in large part to the hybrid nature of these lineages.