title: Chromosomal Mapping of Repetitive DNAs in the Grasshopper Abracris flavolineata Reveal Possible Ancestry of the B Chromosome and H3 Histone Spreading.
abstract: Supernumerary chromosomes (B chromosomes) occur in approximately 15% of eukaryote species. Although these chromosomes have been extensively studied, knowledge concerning their specific molecular composition is lacking in most cases. The accumulation of repetitive DNAs is one remarkable characteristic of B chromosomes, and the occurrence of distinct types of multigene families, satellite DNAs and some transposable elements have been reported. Here, we describe the organization of repetitive DNAs in the A complement and B chromosome system in the grasshopper species Abracris flavolineata using classical cytogenetic techniques and FISH analysis using probes for five multigene families, telomeric repeats and repetitive C0t-1 DNA fractions. The 18S rRNA and H3 histone multigene families are highly variable and well distributed in A. flavolineata chromosomes, which contrasts with the conservation of U snRNA genes and less variable distribution of 5S rDNA sequences. The H3 histone gene was an extensively distributed with clusters occurring in all chromosomes. Repetitive DNAs were concentrated in C-positive regions, including the pericentromeric region and small chromosomal arms, with some occurrence in C-negative regions, but abundance was low in the B chromosome. Finally, the first demonstration of the U2 snRNA gene in B chromosomes in A. flavolineata may shed light on its possible origin. These results provide new information regarding chromosomal variability for repetitive DNAs in grasshoppers and the specific molecular composition of B chromosomes.
authors.affiliation: Universidade Estadual Paulista (UNESP), Instituto de Biociências/IB, Departamento de Biologia, Rio Claro, São Paulo, Brazil.
authors.forename: Danilo
authors.initials: D
authors.lastname: Bueno
authors.forename: Octavio Manuel
authors.initials: OM
authors.lastname: Palacios-Gimenez
authors.forename: Diogo Cavalcanti
authors.initials: DC
authors.lastname: Cabral-de-Mello
mesh_terms: D000818:Animals; D002874:Chromosome Mapping; D059006:Chromosomes, Insect; D020732:Cytogenetic Analysis; D005260:Female; D006110:Grasshoppers / Q000166:cytology / Q000235:genetics*; D006657:Histones / Q000235:genetics*; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D008540:Meiosis; D005810:Multigene Family; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D012342:RNA, Small Nuclear / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid
chemical_list: D006657:Histones; D012337:RNA, Ribosomal, 18S; D012342:RNA, Small Nuclear; C405484:U2 small nuclear RNA