RESUMO
To better understand the structure and variability of the 45S rDNA cistron and its evolutionary dynamics in grasshoppers, we performed a detailed analysis combining classical and molecular cytogenetic data with whole-genome sequencing in Abracris flavolienata, which shows extraordinary variability in the chromosomal distribution for this element. We found astonishing variability in the number and size of rDNA clusters at intra- and inter-population levels. Interestingly, FISH using distinct parts of 45S rDNA cistron (18S rDNA, 28S rDNA, and ITS1) as probes revealed a distinct number of clusters, suggesting independent mobility and amplification of the 45S rDNA components. This hypothesis is consistent with the higher genomic coverage of almost the entire cistron of 45S rDNA observed in A. flavolineata compared to other grasshoppers, besides coverage variability along the 45S rDNA cistron in the species. In addition, these differences in coverage for distinct components of the 45S rDNA cistron indicate emergence of pseudogenes evidenced by existence of truncated sequences, demonstrating the rDNA dynamics in the species. Although the chromosomal distribution of 18S rDNA was highly variable, the chromosomes 1, 3, 6, and 9 harbored rDNA clusters in all individuals with the occurrence of NOR activity in pair 9, suggesting ancestry or selective pressures to prevent pseudogenization of rDNA sequences in this chromosome pair. Additionally, small NORs and cryptic rDNA loci were observed. Finally, there was no evidence of enrichment and association of transposable elements, at least, inside or nearby rDNA cistron. These findings broaden our knowledge of rDNA dynamics, revealing an independent movement and amplification of segments of 45S rDNA cistron, which in A. flavolineata could be attributed to ectopic recombination.
Assuntos
Cromossomos de Insetos/genética , DNA Ribossômico/genética , Gafanhotos/genética , RNA Ribossômico/genética , Animais , Genoma de Inseto , MasculinoRESUMO
The anatomy of the female reproductive system of the grasshopper Abracris flavolineata does not differ substantially from the most Orthoptera. Glandular pouches of Comstock - Kellogg are present and well developed. The spermatheca is single with a distal diverticulate structure. There are two ovaries of the panoistic comb type, each one with 20-22 ovarioles. The pseudocollateral glands are fairly large and conspicuous. The histological studies of the ovariole and spermatheca revealed some distinct features.
A anatomia do aparelho reprodutor feminino do gafanhoto Abracris flavolineata não é muito diferente dos ortópteros em geral. Possui dois ovários panoísticos do tipo pente, contendo 20 a 22 ovaríolos cada. Apresenta glândulas de Comstock - Kellogg bem desenvolvidas; a espermateca é simples, provida de uma estrutura diverticular distal. As glândulas pseudo-colaterais são relativamente grandes e couspícuas. O estudo histológico dos ovaríolos e da espermateca revelou algumas características distintas.
RESUMO
The anatomy of the female reproductive system of the grasshopper Abracris flavolineata does not differ substantially from the most Orthoptera. Glandular pouches of Comstock - Kellogg are present and well developed. The spermatheca is single with a distal diverticulate structure. There are two ovaries of the panoistic comb type, each one with 20-22 ovarioles. The pseudocollateral glands are fairly large and conspicuous. The histological studies of the ovariole and spermatheca revealed some distinct features.
A anatomia do aparelho reprodutor feminino do gafanhoto Abracris flavolineata não é muito diferente dos ortópteros em geral. Possui dois ovários panoísticos do tipo pente, contendo 20 a 22 ovaríolos cada. Apresenta glândulas de Comstock - Kellogg bem desenvolvidas; a espermateca é simples, provida de uma estrutura diverticular distal. As glândulas pseudo-colaterais são relativamente grandes e couspícuas. O estudo histológico dos ovaríolos e da espermateca revelou algumas características distintas.