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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.


Related in: MedlinePlus

Chromomycin A3-positive (CMA+) FISH images of cytogenetically variable Tanacetum species, in which CMA+ bands are marked yellow, 26S-5S rDNA signals and marked orange. (a, b) T. archibaldii (2x) with 56 CMA signals (asterisks indicate interacalary CMA+ bands) and with 4 rDNA signals; (c, d) T. balsamita, 2x, with 40 CMA+ signals (many of them pericentromeric, indicated with asterisks) and with four rDNA signals – a slightly decondensed rDNA is indicated with an arrow; cultivated (e, f) and wild (g,h) T. parthenium (from Shahid Beheshti University, 1633 and Tochal, 1483, respectively), both 2x with 14 and six CMA+ and six and two rDNA signals observed, respectively; (i, j) T. kotschyi (Tabriz, Mishodagh, 1339), 3x, with 44 CMA+ signals and six rDNA signals and (k, l) T. joharchii, 3x, with 24 CMA and six rDNA signals; note faint or interstitial CMA+ bands indicated with asterisks and decondensed rDNAs indicated with arrows in both pictures. Scale bars = 10 μm
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Fig3: Chromomycin A3-positive (CMA+) FISH images of cytogenetically variable Tanacetum species, in which CMA+ bands are marked yellow, 26S-5S rDNA signals and marked orange. (a, b) T. archibaldii (2x) with 56 CMA signals (asterisks indicate interacalary CMA+ bands) and with 4 rDNA signals; (c, d) T. balsamita, 2x, with 40 CMA+ signals (many of them pericentromeric, indicated with asterisks) and with four rDNA signals – a slightly decondensed rDNA is indicated with an arrow; cultivated (e, f) and wild (g,h) T. parthenium (from Shahid Beheshti University, 1633 and Tochal, 1483, respectively), both 2x with 14 and six CMA+ and six and two rDNA signals observed, respectively; (i, j) T. kotschyi (Tabriz, Mishodagh, 1339), 3x, with 44 CMA+ signals and six rDNA signals and (k, l) T. joharchii, 3x, with 24 CMA and six rDNA signals; note faint or interstitial CMA+ bands indicated with asterisks and decondensed rDNAs indicated with arrows in both pictures. Scale bars = 10 μm

Mentions: Table 1 shows the results of fluorochrome banding with chromomycin and FISH assays, and Figs. 2 and 3 present selected representative Tanacetum metaphases. For the sake of clarity, only three chromosomal locations have been considered both for chromomycin A3 (CMA) and rDNA signals, following the treatment used in the www.plantrdnadatabase.com. These are: (peri)centromeric, interstitial and (sub)terminal. Results of chromomycin banding, which stains GC-rich DNA portions, are highly variable within and between Tanacetum species and even among individuals in some cases. In only four species is the number of bands always constant (the diploids T. parthenifolium Sch. Bip., T. persicum (Boiss.) Mozaff., T. pinnatum and T. budjnurdense (Rech.f.) Tzvelev) and low — four, see picture of T. pinnatum (Fig. 2a). However, from a minimum of two CMA+ bands in a wild population of the diploid T. parthenium (Fig. 3g) to a maximum of 66 bands for the diploid T. archibaldii Podlech (Fig. 3a) there are myriad variations. In most cases, however, there is a considerable range of variability within a species. The preferred position is usually (sub)terminal, and sometimes detached or terminal decondensed DNA (probably rDNA) is clearly seen with this staining (see Fig. 3k). Several species also present pericentromeric bands, and in two species (T. archibaldii and T. joharchii), several intercalary signals are also visible (Fig. 3a and 3k). Pericentromeric (and to a lesser extent, intercalary) bands appear in species that already present a high number of GC-rich bands.Fig. 2


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)

Chromomycin A3-positive (CMA+) FISH images of cytogenetically variable Tanacetum species, in which CMA+ bands are marked yellow, 26S-5S rDNA signals and marked orange. (a, b) T. archibaldii (2x) with 56 CMA signals (asterisks indicate interacalary CMA+ bands) and with 4 rDNA signals; (c, d) T. balsamita, 2x, with 40 CMA+ signals (many of them pericentromeric, indicated with asterisks) and with four rDNA signals – a slightly decondensed rDNA is indicated with an arrow; cultivated (e, f) and wild (g,h) T. parthenium (from Shahid Beheshti University, 1633 and Tochal, 1483, respectively), both 2x with 14 and six CMA+ and six and two rDNA signals observed, respectively; (i, j) T. kotschyi (Tabriz, Mishodagh, 1339), 3x, with 44 CMA+ signals and six rDNA signals and (k, l) T. joharchii, 3x, with 24 CMA and six rDNA signals; note faint or interstitial CMA+ bands indicated with asterisks and decondensed rDNAs indicated with arrows in both pictures. Scale bars = 10 μm
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Fig3: Chromomycin A3-positive (CMA+) FISH images of cytogenetically variable Tanacetum species, in which CMA+ bands are marked yellow, 26S-5S rDNA signals and marked orange. (a, b) T. archibaldii (2x) with 56 CMA signals (asterisks indicate interacalary CMA+ bands) and with 4 rDNA signals; (c, d) T. balsamita, 2x, with 40 CMA+ signals (many of them pericentromeric, indicated with asterisks) and with four rDNA signals – a slightly decondensed rDNA is indicated with an arrow; cultivated (e, f) and wild (g,h) T. parthenium (from Shahid Beheshti University, 1633 and Tochal, 1483, respectively), both 2x with 14 and six CMA+ and six and two rDNA signals observed, respectively; (i, j) T. kotschyi (Tabriz, Mishodagh, 1339), 3x, with 44 CMA+ signals and six rDNA signals and (k, l) T. joharchii, 3x, with 24 CMA and six rDNA signals; note faint or interstitial CMA+ bands indicated with asterisks and decondensed rDNAs indicated with arrows in both pictures. Scale bars = 10 μm
Mentions: Table 1 shows the results of fluorochrome banding with chromomycin and FISH assays, and Figs. 2 and 3 present selected representative Tanacetum metaphases. For the sake of clarity, only three chromosomal locations have been considered both for chromomycin A3 (CMA) and rDNA signals, following the treatment used in the www.plantrdnadatabase.com. These are: (peri)centromeric, interstitial and (sub)terminal. Results of chromomycin banding, which stains GC-rich DNA portions, are highly variable within and between Tanacetum species and even among individuals in some cases. In only four species is the number of bands always constant (the diploids T. parthenifolium Sch. Bip., T. persicum (Boiss.) Mozaff., T. pinnatum and T. budjnurdense (Rech.f.) Tzvelev) and low — four, see picture of T. pinnatum (Fig. 2a). However, from a minimum of two CMA+ bands in a wild population of the diploid T. parthenium (Fig. 3g) to a maximum of 66 bands for the diploid T. archibaldii Podlech (Fig. 3a) there are myriad variations. In most cases, however, there is a considerable range of variability within a species. The preferred position is usually (sub)terminal, and sometimes detached or terminal decondensed DNA (probably rDNA) is clearly seen with this staining (see Fig. 3k). Several species also present pericentromeric bands, and in two species (T. archibaldii and T. joharchii), several intercalary signals are also visible (Fig. 3a and 3k). Pericentromeric (and to a lesser extent, intercalary) bands appear in species that already present a high number of GC-rich bands.Fig. 2

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.


Related in: MedlinePlus