Analysis of multiple chromosomal rearrangements in the genome of Willisornis vidua using BAC-FISH and chromosome painting on a supposed conserved karyotype

Abstract

Background Thamnophilidae birds are the result of a monophyletic radiation of insectivorous Passeriformes. They are a diverse group of 225 species and 45 genera and occur in lowlands and lower montane forests of Neotropics. Despite the large degree of diversity seen in this family, just four species of Thamnophilidae have been karyotyped with a diploid number ranging from 76 to 82 chromosomes. The karyotypic relationships within and between Thamnophilidae and another Passeriformes therefore remain poorly understood. Recent studies have identified the occurrence of intrachromosomal rearrangements in Passeriformes using in silico data and molecular cytogenetic tools. These results demonstrate that intrachromosomal rearrangements are more common in birds than previously thought and are likely to contribute to speciation events. With this in mind, we investigate the apparently conserved karyotype of Willisornis vidua, the Xingu Scale-backed Antbird, using a combination of molecular cytogenetic techniques including chromosome painting with probes derived from Gallus gallus (chicken) and Burhinus oedicnemus (stone curlew), combined with Bacterial Artificial Chromosome (BAC) probes derived from the same species. The goal was to investigate the occurrence of rearrangements in an apparently conserved karyotype in order to understand the evolutionary history and taxonomy of this species. In total, 78 BAC probes from the Gallus gallus and Taeniopygia guttata (the Zebra Finch) BAC libraries were tested, of which 40 were derived from Gallus gallus macrochromosomes 1–8, and 38 from microchromosomes 9–28. Results The karyotype is similar to typical Passeriformes karyotypes, with a diploid number of 2n = 80. Our chromosome painting results show that most of the Gallus gallus chromosomes are conserved, except GGA-1, 2 and 4, with some rearrangements identified among macro- and microchromosomes. BAC mapping revealed many intrachromosomal rearrangements, mainly inversions, when comparing Willisornis vidua karyotype with Gallus gallus, and corroborates the fissions revealed by chromosome painting. Conclusions Willisornis vidua presents multiple chromosomal rearrangements despite having a supposed conservative karyotype, demonstrating that our approach using a combination of FISH tools provides a higher resolution than previously obtained by chromosome painting alone. We also show that populations of Willisornis vidua appear conserved from a cytogenetic perspective, despite significant phylogeographic structure.

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

“…Although this diploid number is slightly lower than the "typical" avian karyotype (2n ≈ 80), we detected fissions of chromosomes homologous to ancestral pairs 5 and 6 (NGA5 and NGA6). Chromosome fissions involving the homologous chromosome to NGA5 are frequent in birds and have been reported in species from the following Neoaves orders: Accipitriformes, Charadriiformes, Eurypygiformes, Falconiformes, Gruiformes, Passeriformes, Trogoniformes, Piciformes, and Strigiformes [7,30,[42][43][44][45][46], while fissions in GGA6 have been detected previously only in Psittaciformes species [28,47,48] and in Crotophaga ani, a Cuculiformes species [27]. In addition, four chromosomal associations were detected in P. brasilianus, including associations between macrochromosomes (NGA5/7), macrochromosomes and microchromosomes (NGA8/12 and NGA9/10) and between microchromosomes (NGA11/13).…”

“…Recently, bacterial artificial chromosome (BAC) probes from the genomic libraries of chicken and zebra finch (Taeniopygia guttata, Passeriformes, Neoaves) have been applied successfully across multiple avian species totaling chromosome maps for 36 species from 12 different orders [15,16,[24][25][26][27][28][29][30]. Results from these studies suggested evolutionary stability in avian microchromosome organization, except in Falconiformes, Psittaciformes, and Cuculiformes species, in which microchromosomal fusions were found [15,16,24,25,27,28], demonstrating the usefulness of microchromosome BAC probes to provide a more extensive analysis of chromosomal evolution in birds.…”

Comparative chromosome maps between the stone curlew and three ciconiiform species (the grey heron, little egret and crested ibis)

“…Probes from the stone curlew ( Burhinus oedicnemus , BOE, 2n = 42, Charadriiformes) were the first set of chromosome-specific painting probes from Neoaves species that were able to cover the entire genome of a given bird species [ 24 ]. Thus, BOE painting probes have been used to establish genome-wide chromosomal homology among the karyotypes of eleven avian species in eight different orders [ 24 – 28 ]. The results demonstrate that BOE painting probes are robust tools for delineating avian chromosome evolution, especially for revealing the rearrangements that involve microchromosomes.…”

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

“…Because of technical limitations, however, most of the molecular cytogenetics studies in Passeriformes have focused only on the comparison of homology with chicken macrochromosomes [11]. For instance, up to now, only four Passeriformes species had their karyotype analyzed in detail, i.e., macro and microchromosomes: Taeniopygia guttata, Turdus merula, and Serinus canaria [17,21,22] from oscines suborder, and Willisornis vidua from suboscines suborder [23]. The results revealed that the microchromosomes were not involved in interchromosomal events in the oscines species.…”