Do Exogenous DNA Double-Strand Breaks Change Incomplete Synapsis and Chiasma Localization in the Grasshopper Stethophyma grossum?

PLoS One

Julio S. Rufas¹  Adela Calvente¹  Juan Luis Santos² 

[1] Departamento de Biología, Edificio de Biológicas, Universidad Autónoma de Madrid, Madrid, Spain;Departamento de Genética, Facultad de Biología, Universidad Complutense de Madrid, Madrid, Spain

关键词: Spermatocytes;    Synapsis;    Chromatin;    Homologous recombination;    Homologous chromosomes;    Metaphase;    Anaphase;    Prophase;   

DOI  :  10.1371/journal.pone.0168499

学科分类：医学（综合）

来源: Public Library of Science

【 摘 要 】

Meiotic recombination occurs as a programmed event that initiates by the formation of DNA double-strand breaks (DSBs) that give rise to the formation of crossovers that are observed as chiasmata. Chiasmata are essential for the accurate chromosome segregation and the generation of new combinations of parental alleles. Some treatments that provoke exogenous DSBs also lead to alterations in the recombination pattern of some species in which full homologous synapsis is achieved at pachytene. We have carried out a similar approach in males of the grasshopper Stethophyma grossum, whose homologues show incomplete synapsis and proximal chiasma localization. After irradiating males with γ rays we have studied the distribution of both the histone variant γ-H2AX and the recombinase RAD51. These proteins are cytological markers of DSBs at early prophase I. We have inferred synaptonemal complex (SC) formation via identification of SMC3 and RAD 21 cohesin subunits. Whereas thick and thin SMC3 filaments would correspond to synapsed and unsynapsed regions, the presence of RAD21 is only restricted to synapsed regions. Results show that irradiated spermatocytes maintain restricted synapsis between homologues. However, the frequency and distribution of chiasmata in metaphase I bivalents is slightly changed and quadrivalents were also observed. These results could be related to the singular nuclear polarization displayed by the spermatocytes of this species.

【 授权许可】

CC BY