Repeat Sequence Mapping Shows Different W Chromosome Evolutionary Pathways in Two Caprimulgiformes Families

Abstract

Although birds belonging to order Caprimulgiformes show extensive karyotype variation, data concerning their genomic organization is still scarce, as most studies have presented only results obtained from conventional staining analyses. Nevertheless, some interesting findings have been observed, such as the W chromosome of the Common Potoo, Nyctibius griseus (2n = 86), which has the same morphology and size of the Z chromosome, a rare feature in Neognathae birds. Hence, we aimed to investigate the process by which the W chromosome of this species was enlarged. For that, we analyzed comparatively the chromosome organization of the Common Potoo and the Scissor-tailed Nightjar, Hydropsalis torquata (2n = 74), which presents the regular differentiated sex chromosomes, by applying C-banding, G-banding and mapping of repetitive DNAs (microsatellite repeats and 18S rDNA). Our results showed an accumulation of constitutive heterochromatin in the W chromosome of both species. However, 9 out of 11 microsatellite sequences hybridized in the large W chromosome in the Common Potoo, while none of them hybridized in the W chromosome of the Scissor-tailed Nightjar. Therefore, we can conclude that the accumulation of microsatellite sequences, and consequent increase in constitutive heterochromatin, was responsible for the enlargement of the W chromosome in the Common Potoo. Based on these results, we conclude that even though these two species belong to the same order, their W chromosomes have gone through different evolutionary histories, with an extra step of accumulation of repetitive sequences in the Common Potoo.

Interspecies Chromosome Mapping in Caprimulgiformes, Piciformes, Suliformes, and Trogoniformes (Aves): Cytogenomic Insight into Microchromosome Organization and Karyotype Evolution in Birds

“…The Z sex chromosome is submetacentric and equivalent in size to the third autosomal pair (Figure 1a). Corroborating previous studies, we found 2n = 74 in H. torquata [40], 2n = 112 in P. inscriptus and R. t. tucanus [11], and 2n = 82 in T. s. surrucura [32] (Figure 1b-e, respectively). rate (FDR) approach, with p ≤ 0.05 being considered statistically significant.…”

“…In H. torquata, we found fusions between macrochromosomes (NGA6/10) and between macrochromosomes and microchromosomes (NGA9/13 and NGA8/14). Based on the fact that conventional cytogenetic analyses in Caprimulgiformes species revealed an interesting range of diploid number, from 2n = 68 in Chordeiles pusillus [50] to 2n = 86 in Nyctibius griseus [40], it is plausible to infer that fusions involving microchromosomes and macrochromosomes appear to have played an important role in the chromosome evolution of this group.…”

Comparative cytogenetics in three species of Wood-Warblers (Aves: Passeriformes: Parulidae) reveal divergent banding patterns and chromatic heterogeneity for the W chromosome

“…It is important to emphasize that GTG and RBG bands analyses have already identified a paracentric inversion in the terminal region of the long arm of the Z chromosome in Alectoris chukar (Galliformes) (Ouchia and Ladjali 2018). Signals of hybridization in this chromosome also demonstrated that the accumulation of the repetitive sequences are responsible for the main cause of its enlargement, as in Myiopsitta monachus (Psittaciformes) (Furo et al 2017) and Nyctibius griseus (Caprimulgiformes) (de Souza et al 2020).…”

Karyotype Evolution and Genomic Organization of Repetitive DNAs in the Saffron Finch, Sicalis flaveola (Passeriformes, Aves)

“…To this end, it is essential to know how these elements are organized in the genome. Despite the significance of simple short repetition probes (SSR), data concerning the mapping of these sequences by fluorescent in situ hybridization (FISH) are available for a few species of birds and results so far have shown the involvement of amplification of these elements in atypical sex chromosomes, in which the repetitive DNA amount was related to the enlargement of these elements in some cases [34][35][36][37][38][39][40].…”