A Unique Recent Origin of the Allotetraploid Species Arabidopsis suecica: Evidence from Nuclear DNA Markers

Abstract

A coalescent-based method was used to investigate the origins of the allotetraploid Arabidopsis suecica, using 52 nuclear microsatellite loci typed in eight individuals of A. suecica and 14 individuals of its maternal parent Arabidopsis thaliana, and four short fragments of genomic DNA sequenced in a sample of four individuals of A. suecica and in both its parental species A. thaliana and Arabidopsis arenosa. All loci were variable in A. thaliana but only 24 of the 52 microsatellite loci and none of the four sequence fragments were variable in A. suecica. We explore a number of possible evolutionary scenarios for A. suecica and conclude that it is likely that A. suecica has a recent, unique origin between 12,000 and 300,000 years ago. The time estimates depend strongly on what is assumed about population growth and rates of mutation. When combined with what is known about the history of glaciations, our results suggest that A. suecica originated south of its present distribution in Sweden and Finland and then migrated north, perhaps in the wake of the retreating ice.

RNAi of met1 Reduces DNA Methylation and Induces Genome-Specific Changes in Gene Expression and Centromeric Small RNA Accumulation in Arabidopsis Allopolyploids

“…Modest demethylation levels detected in the A. arenosa centromeres in wild-type A. suecica strains indicate that repressive chromatin constraints were leaky during polyploid formation and evolution. This may be associated with relatively recent events in the formation of natural allopolyploids (Jakobsson et al 2006). The levels of centromeric sensitivity to perturbation in DNA methylation may increase over generational time and hence disrupt normal patterns of meiosis and/or gametogenesis as previously observed (Comai et al 2003), which leads to the increased severity of phenotypic effects in met1-RNAi A. suecica plants.…”

Cis- and trans-regulatory divergence between progenitor species determines gene-expression novelty in Arabidopsis allopolyploids

“…As a result, either At (shown in the diagram) or Aa alleles could increase expression levels. (b) Possible modes of At and Aa allele interactions leading to homoeologous genes expression changes within F1 allotetraploids, among allotetraploid lineages (F8), and a natural allotetraploid (A. suecica) that was formed 12,000-300,000 years ago 41 . Aa trans factors tended to upregulate At alleles, whereas At trans factors tended to either up-or down-regulate Aa alleles.…”

“…Moreover, the majority (~58%) of At and Aa allelic expression changes are in the same direction from F1 to F8 and natural A. suecica lines, supporting a notion of dominant trans regulatory changes during selfing. A. suecica had a single origin at 12,000-300,000 years ago 41 . Combination of predominant cis effects between species and predominant trans effects during selfing might act in concert to provide opportunities for new allopolyploids to increase levels of adaptation and diversification during evolution 3,4 .…”

The BOY NAMED SUE Quantitative Trait Locus Confers Increased Meiotic Stability to an Adapted Natural Allopolyploid of Arabidopsis

“…In the genus Arabidopsis, a natural allopolyploid species, Arabidopsis suecica (Nat), originated from a single hybridization event that took place 20 to 300 thousand years ago (Jakobsson et al, 2006) between Arabidopsis thaliana (n = 5) and Arabidopsis arenosa (n = 8). A. suecica is self-fertile and fecund and is well established in various regions of Fennoscandinavia in Northern Europe (Schmickl and Koch, 2011).…”