<abstract xmlns="http://www.w3.org/1999/xhtml">

<p>Gymnosperms show a significantly higher mean (1C=18.16, 1Cx=16.80) and a narrow range (16.89-fold) of genome sizes as compared with angiosperms. Among the 12 families the largest ranges of 1C values is shown by Ephedraceae (4.73-fold) and Cupressaceae (4.45-fold) which are partly due to polyploidy as 1Cx values vary 2.41 and 1.37-fold respectively. In rest of the families which have only diploid taxa the range of 1C values is from 1.18-fold (Cycadaeae) to 4.36-fold (Podocarpaceae). The question is how gymnosperms acquired such big genome sizes despite the rarity of recent instances of polyploidy. A general survey of different families and genera shows that gymnosperms have experienced both increase and decrease in their genome size during evolution. Various genomic components which have accounted for these large genomes have been discussed. The major contributors are the transposable elements particularly LTR-retrotransposons comprising of <italic>Ty3gypsy</italic>, <italic>Ty1copia</italic> and <italic>gymny</italic> superfamilies which are most widespread. The genomes of gymnosperms have been acquiring diverse LTR-RTs in their long evolution in the absence of any efficient mechanism of their elimination. The epigenetic machinery which silences these large tracts of repeat sequences into the stretches of heterochromatin and the adaptive value of these silenced repeat sequences need further investigation.</p>
</abstract>

Gymnosperms show a significantly higher mean (1C=18.16, 1Cx=16.80) and a narrow range (16.89-fold) of genome sizes as compared with angiosperms. Among the 12 families the largest ranges of 1C values is shown by Ephedraceae (4.73-fold) and Cupressaceae (4.45-fold) which are partly due to polyploidy as 1Cx values vary 2.41 and 1.37-fold respectively. In rest of the families which have only diploid taxa the range of 1C values is from 1.18-fold (Cycadaeae) to 4.36-fold (Podocarpaceae). The question is how gymnosperms acquired such big genome sizes despite the rarity of recent instances of polyploidy. A general survey of different families and genera shows that gymnosperms have experienced both increase and decrease in their genome size during evolution. Various genomic components which have accounted for these large genomes have been discussed. The major contributors are the transposable elements particularly LTR-retrotransposons comprising of Ty3gypsy, Ty1copia and gymny superfamilies which are most widespread. The genomes of gymnosperms have been acquiring diverse LTR-RTs in their long evolution in the absence of any efficient mechanism of their elimination. The epigenetic machinery which silences these large tracts of repeat sequences into the stretches of heterochromatin and the adaptive value of these silenced repeat sequences need further investigation.

Variation and Evolution of Genome Size in Gymnosperms

Research Cell, Amity University Uttar Pradesh

Silvae Genetica

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

{"article-title":"Variation and Evolution of Genome Size in Gymnosperms"}

Gymnosperms show a significantly higher mean (1C=18.16, 1Cx=16.80) and a narrow range (16.89-fold) of genome sizes as compared with angiosperms. Among the 12...

Variation and Evolution of Genome Size in Gymnosperms

Publié en ligne: 25 sept. 2021

Pages: 156 - 169

DOI: https://doi.org/10.2478/sg-2021-0013

Mots clés
genome size evolution, gymnosperms, cycads, conifers, polyploidy, duplicate genes, tandem repeats, retrotranspo-sons, introns

© 2021 Deepak Ohri, published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Variation and Evolution of Genome Size in Gymnosperms

Publié en ligne: 25 sept. 2021

Pages: 156 - 169

DOI: https://doi.org/10.2478/sg-2021-0013

Mots clésgenome size evolution, gymnosperms, cycads, conifers, polyploidy, duplicate genes, tandem repeats, retrotranspo-sons, introns

© 2021 Deepak Ohri, published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Mots clés
genome size evolution, gymnosperms, cycads, conifers, polyploidy, duplicate genes, tandem repeats, retrotranspo-sons, introns