Conserved satellite DNA motif and lack of interstitial telomeric sites in highly rearranged African Nothobranchius killifish karyotypes.

Using African annual killifishes of the genus Nothobranchius from temporary savannah pools with rapid karyotype and sex chromosome evolution, we analyzed the chromosomal distribution of telomeric (TTAGGG) n repeat and Nfu-SatC satellite DNA (isolated from N. furzeri) in 15 species across the Nothobranchius killifish phylogeny, and with Fundulosoma thierryi as an outgroup. Our fluorescence in situ hybridization experiments revealed that all analyzed taxa share the presence of Nfu-SatC repeat but with diverse organization and distribution on chromosomes. Nfu-SatC landscape was similar in conspecific populations of N. guentheri and N. melanospilus but slightly-to-moderately differed between populations of N. pienaari, and between closely related N. kuhntae and N. orthonotus. Inter-individual variability in Nfu-SatC patterns was found in N. orthonotus and N. krysanovi. We revealed mostly no sex-linked patterns of studied repetitive DNA distribution. Only in N. brieni, possessing X 1 X 2 Y multiple sex chromosomes, Nfu-SatC repeat occupied substantial portion of the neo-Y chromosome, similarly as formerly found in the XY sex chromosome system of turquoise killifish N. furzeri and its sister species N. kadleci - representatives not closely related to N. brieni. All studied species further shared patterns of expected telomeric repeats at the ends of all chromosomes and no additional interstitial telomeric sites. In summary, we revealed i) the presence of conserved satDNA class in Nothobranchius clades (a rare pattern among ray-finned fishes), ii) independent trajectories of Nothobranchius sex chromosome diferentiation, with recurrent and convergent accumulation of Nfu-SatC on the Y chromosome in some species, and iii) genus-wide shared tendency to loss of telomeric repeats during interchromosomal rearrangements. Collectively, our findings advance our understanding of genome structure, mechanisms of karyotype reshuffling and sex chromosome differentiation in Nothobranchius killifishes from the genus-wide perspective. This article is protected by copyright. All rights reserved.