Genome size and endoreplication in two pairs of cytogenetically contrasting species of Pulmonaria (Boraginaceae) in Central Europe. Issue 5 (18th August 2022)

• Record Type: Journal Article
• Authors: Koprivý, Lukáš; Fráková, Viera; Kolarčik, Vladislav; Mártonfiová, Lenka; Dudáš, Matej; Mártonfi, Pavol
• Editors: Loureiro, João
• Is Part Of: AoB plants. Volume 14:Issue 5(2022)
• Publication Date: 2022-08-18
• Subjects: Boraginaceae -- endoreplication -- flow cytometry -- genome size -- geophytes -- Pulmonaria; Plants -- Periodicals; Botany -- Periodicals; 580.5
• DOI: 10.1093/aobpla/plac036
• Languages: English
• ISSNs: 2041-2851

Abstract

Abstract: Genome size is species-specific feature and commonly constant in an organism. In various plants, DNA content in cell nucleus is commonly increased in process of endoreplication, cellular-specific multiplication of DNA content without mitosis. This leads to the endopolyploidy, the presence of multiplied chromosome sets in a subset of cells. The relationship of endopolyploidy to species-specific genome size is rarely analysed and is not fully understood. While negative correlation between genome size and endopolyploidy level is supposed, this is species- and lineage-specific. In the present study, we shed light on this topic, exploring both genome size and endoreplication-induced DNA content variation in two pairs of morphologically similar species of Pulmonaria, P. obscura – P. officinalis and P. mollis – P. murinii . We aim (i) to characterize genome size and chromosome numbers in these species using cytogenetic, root-tip squashing and flow cytometry (FCM) techniques; (ii) to investigate the degree of endopolyploidy in various plant organs, including the root, stem, leaf, calyx and corolla using FCM; and (iii) to comprehensively characterize and compare the level of endopolyploidy and DNA content in various organs of all four species in relation to species systematic relationships and genome size variation. We have confirmed the diploid–dysploid nature of chromosome complements, and divergent genome sizes for Pulmonaria species: P. murinii with 2 n = 2 x = 14, 2.31 pg/2C, P. obscura 2 n = 2 x = 14, 2.69 pg/2C, P. officinalis 2 n = 2 x = 16, 2.96 pg/2C and P. mollis 2 n = 2 x = 18, 3.18 pg/2C. Endopolyploidy varies between species and organs, and we have documented 4C–8C in all four organs and up to 32C (64C) endopolyploid nuclei in stems at least in some species. Two species with lower genome sizes tend to have higher endopolyploidy levels than their closest relatives. Endoreplication-generated tissue-specific mean DNA content is increased and more balanced among species in all four organs compared to genome size. Our results argue for the narrow relationship between genome size and endopolyploidy in the present plant group within the genus Pulmonaria, and endopolyploidization seems to play a compensatory developmental role in organs of related morphologically similar species. Abstract : In plants, a negative correlation between species-specific genome size and endopolyploidy level is assumed. We shed light on this topic, exploring both cytogenetic features in two pairs of morphologically similar diploid–dysploid species of Pulmonaria, P. obscura – P. officinalis and P. mollis – P. murinii . We have recognized divergent genome sizes and extensive endopolyploidy, and the latter is suggested to be associated with the geophytic growth form of Pulmonarias. Our results provide evidence for the narrow relationship between genome size and endopolyploidy: species with lower genome sizes tend to have greater endopolyploidy levels and vice versa. Endopolyploidization seems to play a compensatory developmental role in organs of related Pulmonarias.