Genome size variation among accessions of Arabidopsis thaliana.
ABSTRACT Estimates of the amount of nuclear DNA of Arabidopsis thaliana, known to be among the lowest within angiosperms, vary considerably. This study aimed to determine genome size of a range of accessions from throughout the entire Eurasian range of the species.
Twenty accessions from all over Europe and one from Japan were examined using flow cytometry.
Significant differences in mean C-values were detected over a 1.1-fold range. Mean haploid (1C) genome size was 0.215 pg (211 Mbp) for all analysed accessions. Two accessions were tetraploid.
A closer investigation of the DNA fractions involved in intraspecific genome size differences in this experimentally accessible species may provide information on the factors involved in stability and evolution of genome sizes.
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ABSTRACT: Polyploidization and subsequent changes in genome size are fundamental processes in evolution and diversification. Little is currently known about the extent of genome size variation within taxa and the evolutionary forces acting on this variation. Arabidopsis kamchatica has been reported to contain both diploid and tetraploid individuals. The aim of this study was to determine the genome size of A. kamchatica, whether there is variation in ploidy and/or genome size in A. kamchatica, and to study how genome size has evolved. We used propidium iodide flow cytometry to measure 2C DNA content of 73 plants from 25 geographically diverse populations of the putative allotetraploid Arabidopsis kamchatica and its parents, A. lyrata and A. halleri. All A. kamchatica plants appear to be tetraploids. The mean 2C DNA content of A. kamchatica was 1.034 pg (1011 Mbp), which is slightly smaller than the sum of its diploid parents (A.lyrata: 0.502 pg, A. halleri: 0.571 pg). A. kamchatica appears to have lost approximately 37.594 Mbp (3.6%) of DNA from its 2C genome. Tetraploid A. lyrata from Germany and Austria appear to have lost approximately 70.366 Mbp (7.2%) of DNA from the 2C genome, possibly due to hybridization with A. arenosa, which has a smaller genome than A. lyrata. We did find genome size differences among A. kamchatica populations, which varied up to 7%. A. kamchatica ssp. kawasakiana from Japan appears to have a slightly larger genome than A. kamchatica ssp. kamchatica from North America, perhaps due to multiple allopolyploid origins or hybridization with A. halleri. However, the among population coefficient of variation in 2C DNA content is lower in A. kamchatica than in other Arabidopsis taxa. Due to its close relationship to A. thaliana, A. kamchatica has the potential to be very useful in the study of polyploidy and genome evolution.AoB PLANTS 05/2014; · 1.74 Impact Factor
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ABSTRACT: Background Wild relatives in the genus Arabidopsis are recognized as useful model systems to study traits and evolutionary processes in outcrossing species, which are often difficult or even impossible to investigate in the selfing and annual Arabidopsis thaliana. However, Arabidopsis as a genus is littered with sub-species and ecotypes which make realizing the potential of these non-model Arabidopsis lineages problematic. There are relatively few evolutionary studies which comprehensively characterize the gene pools across all of the Arabidopsis supra-groups and hypothesized evolutionary lineages and none include sampling at a world-wide scale. Here we explore the gene pools of these various taxa using various molecular markers and cytological analyses.ResultsBased on ITS, microsatellite, chloroplast and nuclear DNA content data we demonstrate the presence of three major evolutionary groups broadly characterized as A. lyrata group, A. halleri group and A. arenosa group. All are composed of further species and sub-species forming larger aggregates. Depending on the resolution of the marker, a few closely related taxa such as A. pedemontana, A. cebennensis and A. croatica are also clearly distinct evolutionary lineages. ITS sequences and a population-based screen based on microsatellites were highly concordant. The major gene pools identified by ITS sequences were also significantly differentiated by their homoploid nuclear DNA content estimated by flow cytometry. The chloroplast genome provided less resolution than the nuclear data, and it remains unclear whether the extensive haplotype sharing apparent between taxa results from gene flow or incomplete lineage sorting in this relatively young group of species with Pleistocene origins.Conclusions Our study provides a comprehensive overview of the genetic variation within and among the various taxa of the genus Arabidopsis. The resolved gene pools and evolutionary lineages will set the framework for future comparative studies on genetic diversity. Extensive population-based phylogeographic studies will also be required, however, in particular for A. arenosa and their affiliated taxa and cytotypes.BMC Evolutionary Biology 10/2014; 14(1):224. · 3.41 Impact Factor
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ABSTRACT: passed away unexpectedly on 1 July 2012, at his home in Northeim, Germany, due to a heart attack. He was 73 years old. His death brings to a close a remarkably varied ca-reer that made him one of the most prominent and enigmatic plant evolutionary biologists of Continental Europe for the last 30 years. Bachmann, known to many for his work on Microseris (Asteraceae: Lactuceae), made substantial contributions to our understanding of genome size variation in both plants and animals, plant evolu-tionary genetics, and a diverse array of topics in plant molecular biodiversity research. My objective here is to summarize the basic facts of his exceptional career and bring back into memory his many accomplishments that influenced more than one research generation studying plant variation and evolution in natural popula-tions. I had only a few, but memorable, personal encounters with Bachmann: it was his genetic work on Microseris I struggled with during my Ph.D., in the early 1990s, studying the genetic basis of speciation in Senecio (supervised by Joachim W. Kadereit). Born in Leipzig, Germany, on 8 March 1939, Bachmann was educated at the Max-Planck-Gym-nasium in Göttingen (1950–1958), where he published his first scien-tific paper at the age of 18 in the field of archaeology (Bachmann, 1957). Following his studies in Biology/Zoology at the Univer-sities of Göttingen and Munich (1958–1960), he received a master's degree in Biology (. In addition, he served in various committees and editorial boards, e.g., The Netherlands Commission on Genetic Modification (COGEM), Acta Botanica Neerlandica, Molecular Ecology, Plant Species Biology and Plant Systematics and Evolution. Bachmann's scientific pro-file defies placement in any one category due to his kaleidoscopic career history, spanning multiple and partly disparate fields across zoology, genetics, botany and even biomedicine. In a nutshell, he was a developmental animal physiolo-gist by training, an experimental geneticist by inclination, and, from about the late 1970s onwards, a plant evolutionary biologist by much of his professional occupa-tion and outside recognition from the scientific community. This cross-disciplinary experience was a hallmark of his career and likely endowed him with a characteris-tic freedom and courage to think outside the box. Bachmann also had an exceptional knowledge of biological and evolutionary facts and was widely informed about the history and philosophy of science. Konrad Bachmann in his post-retirement (2004) office at the Institute of Plant Genetics and Crop Plant Research (IPK), Gatersleben, Ger-many, in 2007. — Photo credit: IPK Archives.Taxon 03/2013; 62(1):191-195. · 3.05 Impact Factor