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

Abstract

Interchromosomal rearrangements involving microchromosomes are rare events in birds. To date, they have been found mostly in Psittaciformes, Falconiformes, and Cuculiformes, although only a few orders have been analyzed. Hence, cytogenomic studies focusing on microchromosomes in species belonging to different bird orders are essential to shed more light on the avian chromosome and karyotype evolution. Based on this, we performed a comparative chromosome mapping for chicken microchromosomes 10 to 28 using interspecies BAC-based FISH hybridization in five species, representing four Neoaves orders (Caprimulgiformes, Piciformes, Suliformes, and Trogoniformes). Our results suggest that the ancestral microchromosomal syntenies are conserved in Pteroglossus inscriptus (Piciformes), Ramphastos tucanus tucanus (Piciformes), and Trogon surrucura surrucura (Trogoniformes). On the other hand, chromosome reorganization in Phalacrocorax brasilianus (Suliformes) and Hydropsalis torquata (Caprimulgiformes) included fusions involving both macro- and microchromosomes. Fissions in macrochromosomes were observed in P. brasilianus and H. torquata. Relevant hypothetical Neognathae and Neoaves ancestral karyotypes were reconstructed to trace these rearrangements. We found no interchromosomal rearrangement involving microchromosomes to be shared between avian orders where rearrangements were detected. Our findings suggest that convergent evolution involving microchromosomal change is a rare event in birds and may be appropriate in cytotaxonomic inferences in orders where these rearrangements occurred.

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

“…Chicken chromosome 4 hybridized two chromosome pairs in S. flaveola (SFL5 and 12). However, this is the ancestral state, as proposed to the putative Neognathae karyotype [29]. Furthermore, intrachromosomal rearrangements already detected in previous studies in other species of Passeriformes were also observed in the chromosome homologous to GGA1q (SFL2).…”

“…The S. flaveola homologous chromosomes to GGA16 and 25 could not be identified because there were no BAC probes to GGA16, and the probes from GGA25 did not produce signals. Chicken chromosome 4 revealed the GGA4q and 4p as separated chromosomes in S. flaveola (SFL5 and 12), as in the putative Neognathae karyotype [29]. The analysis of different BAC clones corresponding to GGA1 revealed that intrachromosomal rearrangements occurred in SFL2, homologous to GGA1q.…”

“…Interchromosomal rearrangements involving these small elements are rare in birds but have been found only extensively in Falconiformes and Psittaciformes [22,[24][25][26][27]. In addition, microchromosome fusions have been found in Cuculiformes, Suliformes, and Caprimulgiformes species [28,29], and future studies are necessary to investigate if it is a species-specific feature or if it is shared with other members of these orders. Future studies are also necessary for other Passeriformes members, considering the great diversity in the number of species.…”

Microchromosomes are building blocks of bird, reptile and mammal chromosomes

“…However, their number is usually constant and even, as expected for paired autosomes in diploids. Cytological examination, using specific DNA probes, suggests conservation of microchromosomes across 22 avian species (15), and comparative gene mapping and whole-genome analysis attests to considerable conservation among distantly related bird groups (16, 17). Genome sequencing of many bird species now provides unprecedented detail sufficient to compare microchromosomes across avian species.…”

Cytogenetic Evidence Clarifies the Phylogeny of the Family Rhynchocyclidae (Aves: Passeriformes)

“…Although macrochromosomes represent approximately 77% of the average avian genome size, microchromosomes contain around 50% of the avian genes [20][21][22]. Despite the importance of microchromosomes, their organization was studied in few avian orders, and interchromosomal rearrangements involving them have been found only in few orders [12,[23][24][25][26]. Among the Passeriformes, only five species have been investigated: four oscine members, Taeniopygia guttata, Turdus merula, Serinus canaria, and Sicalis flaveola, and one suboscines member, Willisornis vidua [24,27,28].…”