Different Levels of Chromatin Condensation in <b><i>Partamona chapadicola</i></b> and <b><i>Partamona nhambiquara</i></b> (Hymenoptera, Apidae)

Abstract

Studies in several organisms have contributed to the understanding of heterochromatin and its biological importance. In bees of the tribe Meliponini, the presence of chromosomes with totally heterochromatic arms has been attributed to the mechanism of karyotype evolution in which this group accumulated heterochromatin to maintain telomere stability after centric fission events. In the present study, the use of classical and molecular cytogenetic techniques as well as automated image analysis software for the description of the karyotypes of Partamonachapadicola and P. nhambiquara bee species revealed variability in the compaction and patterns of chromatin structure. Although both species have the same chromosome number as other species in the genus Partamona (2n = 34), C-banding and image analyses indicated the existence of chromosomes with 3 regions of different staining intensities, suggesting a chromatin structure with distinct patterns and characteristics. Repetitive DNA probes hybridized only in the euchromatic regions, whereas the regions with intermediate staining intensity did not show any hybridization signals. This suggests that these regions present features more similar to heterochromatin. Evidence of the existence of a chromatin class with intermediate condensation compared to euchromatin and heterochromatin indicates a potential mechanism for heterochromatin amplification and demonstrates the need for further studies on this topic. This previously unrecognized class of chromatin should be taken into account in the study of all Meliponini chromosomes.

Chromosomal mapping of repetitive DNA in Melipona seminigra merrillae Cockerell, 1919 (Hymenoptera, Apidae, Meliponini)

“…Results of chromosome staining by base-specific fluorophores in M. seminigra merrillae were similar to that described in a number of other Meliponini species belonging to group II ( Rocha et al 2003 ; Miranda et al 2013 ; Andrade-Souza et al 2018 ; Cunha et al 2018 ). Several authors have suggested that CMA 3 + markings in Meliponini have a strong correlation with NORs ( Rocha et al 2007 ; Lopes et al 2011 ; Lopes et al 2012 ). Studies of the genus Melipona frequently report a chromosome pair strongly marked by CMA 3 .…”

Organização cromossômica e dinâmica evolutiva de sequências repetitivas em formigas cultivadoras de fungos (Myrmicinae: Attini: Attina)

“…The microsatellites do not cluster in any specific region of the A. cephalotes chromosomes, similar to the pattern observed for a population of M. holmgreni (Barros et al, 2018) and bees (Piccoli et al, 2018;Travenzoli et al, 2019a, b;Lopes et al, 2020;Barbosa et al, 2021), mainly the Melipona species of group I (with a low proportion of heterochromatin restricted to pericentromeric regions). It contrasts to some populations of M. holmgreni, in which the (GA)15 microsatellite is clustered in one or two chromosomal pairs (Micolino et al, 2019).…”

“…This pattern was also observed in other Atta species (Teixeira et al, in prep.). The euchromatic location of microsatellites is common in insects Travenzoli et al, 2019a, b;Lopes et al, 2020). Associations between microsatellites and transposable elements have been previously observed in different organisms, indicating that mobile elements may also be involved in both the origin and the genomic propagation of microsatellites .…”

“…In some grasshoppers' karyotypes, microsatellites have shown scattered or clustered distribution only in euchromatin . Among Hymenoptera, in bees of the genera Melipona Illiger, 1806 and Partamona Schwarz (1939), microsatellites including di-and tri-nucleotides are observed in euchromatic regions (Piccoli et al, 2018;Travenzoli et al, 2019a, b;Lopes et al, 2020). An exception is (CA)15, which shows a scattered distribution only in the heterochromatin of Melipona seminigra merrilae Cockerell, 1919 (Barbosa et al, 2021).…”

Karyotype conservation and genomic organization of repetitive sequences in the leaf-cutting ant Atta cephalotes (Linnaeus, 1758) (Formicidae: Myrmicinae)

“…This pattern was also observed in other Atta species (Teixeira et al 2022). The euchromatic location of microsatellites is common in insects (Palacios-Gimenez and Cabral-de-Mello 2015; Ruiz-Ruano et al 2015;Travenzoli et al 2019aTravenzoli et al , 2019bLopes et al 2020). Associations between microsatellites or satellite DNA and transposable elements have been previously observed in different organisms, indicating that mobile elements may also be involved in both the origin and the genomic propagation of microsatellites (Ellegren 2004;Zhang 2004;Palomeque et al 2006;Ruiz-Ruano et al 2015).…”