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The striking and unexpected cytogenetic diversity of genus Tanacetum L. (Asteraceae): a cytometric and fluorescent in situ hybridisation study of Iranian taxa.

Olanj N, Garnatje T, Sonboli A, Vallès J, Garcia S - BMC Plant Biol. (2015)

Bottom Line: We found striking cytogenetic diversity both in the number of GC-rich bands and rDNA loci.Reconstruction of ancestral genome size, number of CMA+ bands and number of rDNA loci show that ups and downs have occurred during the evolution of these traits, although genome size has mostly increased and the number of CMA+ bands and rDNA loci have decreased in present-day taxa compared with ancestral values.The labile scenario found in Tanacetum proves that some cytogenetic features previously regarded as relatively constant, or even diagnostic, can display high variability, which is better interpreted within a phylogenetic context.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Faculty of Basic Science, Malayer University, Malayer, Iran. n.olanj@malayeru.ac.ir.

ABSTRACT

Background: Although karyologically well studied, the genus Tanacetum (Asteraceae) is poorly known from the perspective of molecular cytogenetics. The prevalence of polyploidy, including odd ploidy warranted an extensive cytogenetic study. We studied several species native to Iran, one of the most important centres of diversity of the genus. We aimed to characterise Tanacetum genomes through fluorochrome banding, fluorescent in situ hybridisation (FISH) of rRNA genes and the assessment of genome size by flow cytometry. We appraise the effect of polyploidy and evaluate the existence of intraspecific variation based on the number and distribution of GC-rich bands and rDNA loci. Finally, we infer ancestral genome size and other cytogenetic traits considering phylogenetic relationships within the genus.

Results: We report first genome size (2C) estimates ranging from 3.84 to 24.87 pg representing about 11 % of those recognised for the genus. We found striking cytogenetic diversity both in the number of GC-rich bands and rDNA loci. There is variation even at the population level and some species have undergone massive heterochromatic or rDNA amplification. Certain morphometric data, such as pollen size or inflorescence architecture, bear some relationship with genome size. Reconstruction of ancestral genome size, number of CMA+ bands and number of rDNA loci show that ups and downs have occurred during the evolution of these traits, although genome size has mostly increased and the number of CMA+ bands and rDNA loci have decreased in present-day taxa compared with ancestral values.

Conclusions: Tanacetum genomes are highly unstable in the number of GC-rich bands and rDNA loci, although some patterns can be established at the diploid and tetraploid levels. In particular, aneuploid taxa and some odd ploidy species show greater cytogenetic instability than the rest of the genus. We have also confirmed a linked rDNA arrangement for all the studied Tanacetum species. The labile scenario found in Tanacetum proves that some cytogenetic features previously regarded as relatively constant, or even diagnostic, can display high variability, which is better interpreted within a phylogenetic context.

No MeSH data available.


Ancestral state reconstruction of number of rDNA signals (left) and genome size (right) for diploid Tanacetum taxa. The model of reconstruction was Parsimony as implemented in Mesquite (v.3.02), and ancestral state reconstruction was estimated using the 50 % majority-rule consensus topology obtained by Bayesian inference phylogenetic analysis of the internal transcribed spacer 1 (ITS1), ITS2 and trnH-psbA data sequence. The Bayesian clade-credibility values (posterior probability > 0.5) are given above branches. Schematic representation of chromosomes with the most commonly found numbers of rDNA signals and bars that depict genome sizes (2C values) with a red line indicating the mean 2C value at the diploid level. (*) Tanacetum polycephalum ssp. argyrophyllum
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Fig4: Ancestral state reconstruction of number of rDNA signals (left) and genome size (right) for diploid Tanacetum taxa. The model of reconstruction was Parsimony as implemented in Mesquite (v.3.02), and ancestral state reconstruction was estimated using the 50 % majority-rule consensus topology obtained by Bayesian inference phylogenetic analysis of the internal transcribed spacer 1 (ITS1), ITS2 and trnH-psbA data sequence. The Bayesian clade-credibility values (posterior probability > 0.5) are given above branches. Schematic representation of chromosomes with the most commonly found numbers of rDNA signals and bars that depict genome sizes (2C values) with a red line indicating the mean 2C value at the diploid level. (*) Tanacetum polycephalum ssp. argyrophyllum

Mentions: Statistical analyses at the genus level should consider phylogenetic relationships among taxa to be as unbiased as possible. However, due to lack of enough data, these comparisons could not be done in most cases. Still, we detected significant and positive correlations using the phylogenetic generalised least squares method (PGLS) between genome size (2C), ploidy, and number of rDNA signals (p < 0.0001), i.e. all parameters increase/decrease in concert. The reconstruction of character evolution into the phylogeny (Fig. 4), based on diploid taxa, provides ancestral 2C values ranging from 7.98 to 8.84 pg, from 10 to 13 for CMA+ bands, and from 4 to 6 rDNA signals for Tanacetum species.Fig. 4


The striking and unexpected cytogenetic diversity of genus Tanacetum L. (Asteraceae): a cytometric and fluorescent in situ hybridisation study of Iranian taxa.

Olanj N, Garnatje T, Sonboli A, Vallès J, Garcia S - BMC Plant Biol. (2015)

Ancestral state reconstruction of number of rDNA signals (left) and genome size (right) for diploid Tanacetum taxa. The model of reconstruction was Parsimony as implemented in Mesquite (v.3.02), and ancestral state reconstruction was estimated using the 50 % majority-rule consensus topology obtained by Bayesian inference phylogenetic analysis of the internal transcribed spacer 1 (ITS1), ITS2 and trnH-psbA data sequence. The Bayesian clade-credibility values (posterior probability > 0.5) are given above branches. Schematic representation of chromosomes with the most commonly found numbers of rDNA signals and bars that depict genome sizes (2C values) with a red line indicating the mean 2C value at the diploid level. (*) Tanacetum polycephalum ssp. argyrophyllum
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4494159&req=5

Fig4: Ancestral state reconstruction of number of rDNA signals (left) and genome size (right) for diploid Tanacetum taxa. The model of reconstruction was Parsimony as implemented in Mesquite (v.3.02), and ancestral state reconstruction was estimated using the 50 % majority-rule consensus topology obtained by Bayesian inference phylogenetic analysis of the internal transcribed spacer 1 (ITS1), ITS2 and trnH-psbA data sequence. The Bayesian clade-credibility values (posterior probability > 0.5) are given above branches. Schematic representation of chromosomes with the most commonly found numbers of rDNA signals and bars that depict genome sizes (2C values) with a red line indicating the mean 2C value at the diploid level. (*) Tanacetum polycephalum ssp. argyrophyllum
Mentions: Statistical analyses at the genus level should consider phylogenetic relationships among taxa to be as unbiased as possible. However, due to lack of enough data, these comparisons could not be done in most cases. Still, we detected significant and positive correlations using the phylogenetic generalised least squares method (PGLS) between genome size (2C), ploidy, and number of rDNA signals (p < 0.0001), i.e. all parameters increase/decrease in concert. The reconstruction of character evolution into the phylogeny (Fig. 4), based on diploid taxa, provides ancestral 2C values ranging from 7.98 to 8.84 pg, from 10 to 13 for CMA+ bands, and from 4 to 6 rDNA signals for Tanacetum species.Fig. 4

Bottom Line: We found striking cytogenetic diversity both in the number of GC-rich bands and rDNA loci.Reconstruction of ancestral genome size, number of CMA+ bands and number of rDNA loci show that ups and downs have occurred during the evolution of these traits, although genome size has mostly increased and the number of CMA+ bands and rDNA loci have decreased in present-day taxa compared with ancestral values.The labile scenario found in Tanacetum proves that some cytogenetic features previously regarded as relatively constant, or even diagnostic, can display high variability, which is better interpreted within a phylogenetic context.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Faculty of Basic Science, Malayer University, Malayer, Iran. n.olanj@malayeru.ac.ir.

ABSTRACT

Background: Although karyologically well studied, the genus Tanacetum (Asteraceae) is poorly known from the perspective of molecular cytogenetics. The prevalence of polyploidy, including odd ploidy warranted an extensive cytogenetic study. We studied several species native to Iran, one of the most important centres of diversity of the genus. We aimed to characterise Tanacetum genomes through fluorochrome banding, fluorescent in situ hybridisation (FISH) of rRNA genes and the assessment of genome size by flow cytometry. We appraise the effect of polyploidy and evaluate the existence of intraspecific variation based on the number and distribution of GC-rich bands and rDNA loci. Finally, we infer ancestral genome size and other cytogenetic traits considering phylogenetic relationships within the genus.

Results: We report first genome size (2C) estimates ranging from 3.84 to 24.87 pg representing about 11 % of those recognised for the genus. We found striking cytogenetic diversity both in the number of GC-rich bands and rDNA loci. There is variation even at the population level and some species have undergone massive heterochromatic or rDNA amplification. Certain morphometric data, such as pollen size or inflorescence architecture, bear some relationship with genome size. Reconstruction of ancestral genome size, number of CMA+ bands and number of rDNA loci show that ups and downs have occurred during the evolution of these traits, although genome size has mostly increased and the number of CMA+ bands and rDNA loci have decreased in present-day taxa compared with ancestral values.

Conclusions: Tanacetum genomes are highly unstable in the number of GC-rich bands and rDNA loci, although some patterns can be established at the diploid and tetraploid levels. In particular, aneuploid taxa and some odd ploidy species show greater cytogenetic instability than the rest of the genus. We have also confirmed a linked rDNA arrangement for all the studied Tanacetum species. The labile scenario found in Tanacetum proves that some cytogenetic features previously regarded as relatively constant, or even diagnostic, can display high variability, which is better interpreted within a phylogenetic context.

No MeSH data available.