Immunodetection of the Synaptonemal Complex in Achiasmate Meiosis of Scorpions

SCHNEIDER M.C.; PIGOZZI M.I.

Foz do Iguacu

Congreso; 21st International Chromosome Conference; 2016

The synaptonemal complex (SC) is a meiosis-specific proteinaceous structureevolutionarily conserved in a wide variety of taxa. It isrelated to specific events, such as homologous pairing, synapsis, recombination,and chromosome disjunction. The formation of SC isessential for genetic recombination; however, its presence does not indicatethe occurrence of crossing over. In scorpions, all speciescytogenetically investigated up to now seem to have an achiasmaticmode of meiosis in males but with the formation of SC. For thefirst time, we studied the SC in scorpions using immunostaining. Theanalyses were accomplished in 3 Brazilian scorpion species, one with monocentric chromosomes (Bothriurus rochai) and two with holocentric chromosomes (Ananteris balzanii and Tityusstrandi). Microspead spermatocytes were subject to immunodetection using acommercial antibody against the protein SMC3, which recognizes a cohesin component along vertebrate SCs, anddetected with a secondary antibody conjugated to Alexa Fluor-488fluorochrome. In pachytene cells of the 3 scorpion species, theimmunostaining showed well-preserved SCs, which allowed theidentification of their entire length. These characteristics of the SC were similar between species with monocentric and holocentric chromosomes. Additionally, some nuclei of A. balzanii presentedsingle filaments non-synapsed axes in terminal and/or interstitialregions of 1 or 2 SCs. These results reveal that the commercial antibodyagainst SMC3 from vertebrates can also be useful to detect this cohesin component in scorpions, including chromosome regions with atypical synaptic behavior. In all species, the SCs weremaintained until the postpachytene substage of meiosis. In species with achiasmate meiosis, the presence of SC in late prophase I cellsseems to be important to maintain the connection betweenhomologous chromosomes, ensuring balanced chromosome segregation.