Abstract
Repetitive DNAs are the main components of eukaryotic genome. We mapped the 18S rDNA and TTAGG telomeric probe sequences by FISH to meiotic chromosomes of eight species of the order Psocoptera considered a basal taxon of Paraneoptera: Valenzuela burmeisteri (Brauer, 1876), Stenopsocus lachlani Kolbe, 1960, Graphopsocus cruciatus (Linnaeus, 1768), Peripsocus phaeopterus (Stephens, 1836), Philotarsus picicornis (Fabricius, 1793), Amphigerontia bifasciata (Latreille, 1799), Psococerastis gibbosa (Sulzer, 1766), and Metylophorus nebulosus (Stephens, 1836). These species belong to five distantly related families of the largest psocid suborder Psocomorpha: Caeciliusidae, Stenopsocidae, Peripsocidae, Philotarsidae, and Psocidae. We show that all the examined species share a similar location of 18S rDNA on a medium-sized pair of autosomes. This is the first study of rDNA clusters in the order Psocoptera using FISH. We also demonstrate that these species have the classical insect (TTAGG)n telomere organization. Our results provide a foundation for further cytogenetic characterization and chromosome evolution studies in Psocoptera.
Highlights
Psocoptera are a small insect order considered a basal taxon of Paraneoptera (Yoshizawa and Saigusa 2001)
18S rDNA and (TTAGG)n telomeric FISH in Psocoptera in situ hybridization (FISH) has become the most important technique for tracing individual chromosomes in holokinetic insects (e.g., Panzera et al 2012, 2015, Maryańska-Nadachowska et al 2013, 2018, Mandrioli et al 2014, Kuznetsova et al 2015, Anjos et al 2016, Golub et al 2017, Salanitro et al 2017, Grozeva et al 2019). It was shown in some case studies that species with the same chromosome complement differ in the number and location of rDNA sites (Panzera et al 2012, 2015, Maryańska-Nadachowska et al 2013, Golub et al 2017)
We demonstrate that the above species, belonging to five different families of the largest suborder Psocomorpha (Caeciliusidae, Stenopsocidae, Peripsocidae, Philotarsidae, and Psocidae), are characterized by conserved karyotypes in respect to telomere composition and rDNA location
Summary
Psocoptera (booklice and barklice) are a small insect order considered a basal taxon of Paraneoptera (Yoshizawa and Saigusa 2001). Based on the results obtained, the authors had concluded that NORs (nucleolus organizer regions) were located differently in these species: on an autosomal bivalent, on the X chromosome, and on the neo-XY bivalent, respectively.
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