Satellitome Analysis in the Southern Lapwing (Vanellus chilensis) Genome: Implications for SatDNA Evolution in Charadriiform Birds

Abstract

Vanellus (Charadriidae; Charadriiformes) comprises around 20 species commonly referred to as lapwings. In this study, by integrating cytogenetic and genomic approaches, we assessed the satellite DNA (satDNA) composition of one typical species, Vanellus chilensis, with a highly conserved karyotype. We additionally underlined its role in the evolution, structure, and differentiation process of the present ZW sex chromosome system. Seven distinct satellite DNA families were identified within its genome, accumulating on the centromeres, microchromosomes, and the W chromosome. However, these identified satellite DNA families were not found in two other Charadriiformes members, namely Jacana jacana and Calidris canutus. The hybridization of microsatellite sequences revealed the presence of a few repetitive sequences in V. chilensis, with only two out of sixteen displaying positive hybridization signals. Overall, our results contribute to understanding the genomic organization and satDNA evolution in Charadriiform birds.

Keywords: Charadriidae; chromosome evolution; constitutive heterochromatin; repetitive DNA; sex chromosomes.

Figure 1

Repeat landscape of male (A) and female (B) V. chilensis showing abundance (Y axis) and Kimura-2-divergence (X axis) of all uncovered VchSatDNAs.

Figure 2

Mitotic chromosome spreads of V. chilensis (VCH) female individuals after FISH using VchSatDNAs (a–e) and (CGG)_n microsatellite (f) probes. Their family names are indicated in the lower right corner in red (Atto550-dUTP labeled). The Z chromosome was assigned arbitrarily based on its morphology, representing an unpaired submetacentric macrochromosome, whereas the W chromosome was properly recognized by a sequential hybridization with the microsatellite (GAA)n. The Z and W sex chromosomes are also indicated in each metaphase. Scale bar = 20 μm.

Figure 3

Mitotic chromosome spreads of V. chilensis (VCH) male individuals after FISH using (GAA)_n microsatellite (a) and VchSatDNAs (b,c) probes. Their family names are indicated in the lower right corner in red (Atto550-dUTP labeled). The Z chromosomes were assigned arbitrarily based on its morphology, representing a large submetacentric macrochromosomal pair. Scale Bar = 20 μm.

Figure 4

Intraspecific genomic hybridization using male (green) and female (red) genomic DNA probes from V. chilensis (VCH) hybridized on female metaphasic chromosomes. (a) DAPI staining (blue), (b) hybridization pattern of the male-derived probe (green), (c) hybridization pattern of the female-derived probe (red), and (d) merged images of both genomic probes and DAPI staining. The common regions for male and female genomes are depicted in yellow. Sequential hybridization with (GAA)n probe (e) and C-banding (f) performed to correctly identify the W chromosome are boxed. The Z chromosome was assigned arbitrarily based on its morphology, representing an unpaired submetacentric macrochromosome. The Z and W sex chromosomes in metaphase are indicated in each slide. Scale bar = 20 μm.