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.
"It has been correlated with several environmental traits, affecting the plant life-histories (Bennett 1972; Nandini and Murray 1997; Price and Bachmann 1975), phenology (Baranyi and Greilhuber 1999; Grime and Mowforth 1982) and plant species distribution (Bennett 1976; Bottini et al. 2000; Knight and Ackerly 2002; Levin and Funderburg 1979; Mac Gillivray and Grime 1995; Ohri and Khoshoo 1986; Poggio et al. 1989, 1998; Wakamiya et al. 1993). Moreover, correlations between DNA variation and geographic or climatic parameters were suggested for many plant species (Bennett 1995; Caceres et al. 1998; Rayburn and Auger 1990; Schmuths et al. 2004; Temsch and Greilhuber 2000, 2001). Considering Lathyrus species, the DNA content variation observed in a few species of the Northern Hemisphere was associated to the life cycles, breeding systems (Nandini and Murray 1997; Rees and Hazarika 1969; Rees and Narayan 1988) and to the frequency of chiasmata in meiotic cells (Narayan and McIntre 1989). "
[Show abstract][Hide abstract] ABSTRACT: The genome size was surveyed in 13 Notolathyrus species endemic to South America by flow cytometry and analyzed in an evolutionary and biogeographic context. A DNA content variation of 1.7-fold was registered, and four groups of species with different DNA content were determined. Although, the 2C values were correlated with the total chromosome length and intrachromosomal asymmetry index (A1), the karyotype formula remained almost constant. The conservation of the karyotype formula is in agreement with proportional changes of DNA in the chromosome arms. Species with annual life cycle and shorter generation time had the lowest DNA content and the data suggest that changes in DNA content involved reductions of genome size in the perennial to annual transitions. The variation of 2C values was correlated with precipitation of the coldest quarter and, to some extent, with altitude. Additional correlations with other variables were observed when the species were analyzed separately according to the biogeographic regions. In general, the species with higher DNA content were found in more stable environments. The bulk of evidence suggests that changes on genome size would have been one of the most important mechanisms that drove or accompanied the diversification of Notolathyrus species.
Journal of Plant Research 05/2014; 127(4). DOI:10.1007/s10265-014-0637-z · 1.82 Impact Factor
"This result suggests that the contigs were mapped to the same A. thaliana genes because they are homologs rather than because they are partial sequences derived from different regions of the same genes by incomplete assembly. This is consistent with Dipterocarpaceae having a larger genome size than A. thaliana (Ohri & Kumar 1986; Schmuths et al. 2004) and thus possibly more genes (Hou & Lin 2009). Therefore , we treated these contigs as different genes in the following analyses. "
[Show abstract][Hide abstract] ABSTRACT: Community-level mass flowering, known as general flowering, which occurs in South-East Asia at supra-annual irregular intervals, is considered a particularly spectacular phenomenon in tropical ecology. Recent studies have proposed several proximate factors inducing general flowering, such as drought and falls in minimum temperature. However, limited empirical data on the developmental and physiological processes have been available to test the significance of such factors. To overcome this limitation and test the hypotheses that general flowering is triggered by the proposed factors, we conducted an 'ecological transcriptome' study of a mass flowering species, Shorea beccariana, comparing meteorological data with genome-wide expression patterns obtained using next-generation sequencing. Among the 98 flowering-related genes identified, the homologs of a floral pathway integrator, SbFT, and a floral repressor, SbSVP, showed dramatic transcriptional changes before flowering, and their flowering functions were confirmed using transgenic Arabidopsis thaliana. Expression in drought-responsive and sucrose-induced genes also changed before flowering. All these expression changes occurred when the flowering-inducing level of drought was reached, as estimated using data from the preceding 10 years. These genome-wide expression data support the hypothesis that drought is a trigger for general flowering.
"Several studies found a correlation of genome size with life history, breeding system, and ecology within several taxonomic groups (Albach and Greilhuber 2004; Weiss- Schneeweiss et al. 2006) and even within single species. Within-species genome size variation has been found in samples from geographically separated populations (Jakob et al. 2004; Schmuths et al. 2004; S ˇ marda and Bureš 2006), while in other cases variation in DNA content was correlated with ecological differences (Kalendar et al. 2000; Knight and Ackerly 2002; Jakob et al. 2004) or with differences in plant phenotype (Knight et al. 2005; Murray 2005; Beaulieu et al. 2007; Achigan-Dako et al. 2008). However, neither spatial pattern nor correlation of genome size with vegetation types or microclimatic conditions was found in a highly variable population of Festuca pallens Host (S ˇ marda et al. 2008). "
[Show abstract][Hide abstract] ABSTRACT: Allium subgenus Melanocrommyum is a species-rich group of perennial onions with quite uniform karyology, ecology and breeding system. Thus, the cytological, ecological and physiological factors often correlated with genome size should have negligible effect on genome size variation in Melanocrommyum. We measured DNA content in subgenus Melanocrommyum using flow cytometry based on propidium iodide staining and analyzed the evolution of genome size in a phylogenetic context. The observed 2C genome size variation in 160 accessions of 70 species of the subgenus is quite high, varying from 26.26 to 78.73 pg. The significant phylogenetic signal in genome size data suggests that distribution of genome size is in accordance with phylogenetic clades identified by the analysis of nuclear ITS sequences. Estimation of ancestral genome sizes using generalized least squares revealed lineages with increasing as well as decreasing DNA content. We found within species genome size variation to be mostly below 2.5%. In species where intraspecific genome size differences were in a range of 6 – 9% they indicate the occurrence of cryptic species, as previously inferred by molecular markers. Thus, genome size variation reflects incipient speciation or diversification in Allium subgenus Melanocrommyum. About two-fold differences in DNA content in several Melanocrommyum species indicate the occurrence of diploid and tetraploid cytotypes in these taxa, which for some species has been confirmed by chromosome counts.
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