title: U1 snDNA clusters in grasshoppers: chromosomal dynamics and genomic organization.
abstract: The spliceosome, constituted by a protein set associated with small nuclear RNA (snRNA), is responsible for mRNA maturation through intron removal. Among snRNA genes, U1 is generally a conserved repetitive sequence. To unveil the chromosomal/genomic dynamics of this multigene family in grasshoppers, we mapped U1 genes by fluorescence in situ hybridization in 70 species belonging to the families Proscopiidae, Pyrgomorphidae, Ommexechidae, Romaleidae and Acrididae. Evident clusters were observed in all species, indicating that, at least, some U1 repeats are tandemly arrayed. High conservation was observed in the first four families, with most species carrying a single U1 cluster, frequently located in the third or fourth longest autosome. By contrast, extensive variation was observed among Acrididae, from a single chromosome pair carrying U1 to all chromosome pairs carrying it, with occasional occurrence of two or more clusters in the same chromosome. DNA sequence analysis in Eyprepocnemis plorans (species carrying U1 clusters on seven different chromosome pairs) and Locusta migratoria (carrying U1 in a single chromosome pair) supported the coexistence of functional and pseudogenic lineages. One of these pseudogenic lineages was truncated in the same nucleotide position in both species, suggesting that it was present in a common ancestor to both species. At least in E. plorans, this U1 snDNA pseudogenic lineage was associated with 5S rDNA and short interspersed elements (SINE)-like mobile elements. Given that we conclude in grasshoppers that the U1 snDNA had evolved under the birth-and-death model and that its intragenomic spread might be related with mobile elements.
authors.affiliation: Departamento de Biologia, Instituto de Biociências/IB, UNESP-Universidade Estadual Paulista, Rio Claro, Brazil.
authors.forename: A
authors.initials: A
authors.lastname: Anjos
authors.affiliation: Departamento de Genética, Facultad de Ciencias, UGR-Universidad de Granada, Granada, Spain.
authors.forename: F J
authors.initials: FJ
authors.lastname: Ruiz-Ruano
authors.affiliation: Departamento de Genética, Facultad de Ciencias, UGR-Universidad de Granada, Granada, Spain.
authors.forename: J P M
authors.initials: JP
authors.lastname: Camacho
authors.affiliation: Departamento de Genética, Centro de Ciências Biológicas/CCB, UFPE-Universidade Federal de Pernambuco, Recife, Brazil.
authors.forename: V
authors.initials: V
authors.lastname: Loreto
authors.affiliation: Departamento de Genética, Facultad de Ciencias, UGR-Universidad de Granada, Granada, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Cabrero
authors.affiliation: Departamento de Genética, Centro de Ciências Biológicas/CCB, UFPE-Universidade Federal de Pernambuco, Recife, Brazil.
authors.forename: M J
authors.initials: MJ
authors.lastname: de Souza
authors.affiliation: Departamento de Biologia, Instituto de Biociências/IB, UNESP-Universidade Estadual Paulista, Rio Claro, Brazil.
authors.forename: D C
authors.initials: DC
authors.lastname: Cabral-de-Mello
mesh_terms: D000818:Animals; D005075:Biological Evolution; D002874:Chromosome Mapping; D002875:Chromosomes; D017124:Conserved Sequence; D005260:Female; D049750:Genome, Insect; D006110:Grasshoppers / Q000235:genetics*; D008297:Male; D008969:Molecular Sequence Data; D005810:Multigene Family; D017412:Ribonucleoprotein, U1 Small Nuclear / Q000235:genetics*
chemical_list: D017412:Ribonucleoprotein, U1 Small Nuclear