Abstract
ABSTRACTAchiasmatic male meiosis in scorpions is characterized by a high frequency of gaps, asynaptic regions and multivalent associations. Here, we performed an immunocytogenetic analysis to investigate recombination, and synapsis and chromatin-remodeling events during meiosis of the scorpion Tityus silvestris. Our results demonstrate that the synaptonemal complex (SC) begins its organization in the zygotene stage and persists until metaphase I. The advancement of the synaptic process is related to the epigenetic modification histone H3 lysine 27 trimethylation (H3K27m3). The distribution and dynamics patterns of variant γH2AX and recombinase Rad51 during achiasmatic meiosis suggests formation and repair of DNA double-strand breaks (DSBs) during early stages of prophase I. The epigenetic modifications, histone H3 lysine 4 trimethylation (H3K4m3) and histone H3 lysine 9 acetylation (H3K9ac), showed a dispersed distribution along the bivalents, suggesting that transcriptional activity is maintained constitutively during prophase I. However, H3K9ac modifications are absent in constitutive heterochromatin carrying the 45S rDNA in pachytene and post-pachytene stages. Collectively, our data demonstrate that T. silvestris exhibits adaptations to the achiasmatic mode, and suggest that epigenetic modifications may act in the regulation of these mechanisms to favor the normal continuation of meiosis in this scorpion.
Highlights
Tityus is the largest genus of the Buthidae family in the Neotropical region, comprising about 200 described species, some of which are of great medical importance (Kovarík et al, 2013; Lourenço, 2002, 2015)
Fluorescence in situ hybridization (FISH) using 45S rDNA showed that this sequence is co-localized with the heterochromatin of pair 1 (Fig. 1D)
Synaptic dynamics in T. silvestris In the present study, we demonstrated that synapsis in T. silvestris is initiated at terminal regions, arranged in a bouquet configuration, during the leptotene–zygotene transition (Fig. 2)
Summary
Tityus is the largest genus of the Buthidae family in the Neotropical region, comprising about 200 described species, some of which are of great medical importance (Kovarík et al, 2013; Lourenço, 2002, 2015). In recent years, these scorpions have been the subject of several meiotic studies, reflecting the fact that they exhibit extensive multivalent associations during metaphase I. The presence of holocentric chromosomes favors fixation of these rearrangements in several natural populations (Mattos et al, 2013) Direct consequences of such changes are detected during prophase I events, as evidenced by synaptic anomalies, such as gaps, asynapsed regions, loop-like structures and a high frequency of heterosynapsis, in several members of this genus (Schneider et al, 2009b)
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