Characterization of Two Satellite DNA Families in the Genome of the Oomycete Plant Pathogen .

Satellite DNA is a class of repetitive sequences that are organized in long arrays of tandemly repeated units in most eukaryotes. Long considered as selfish DNA, satellite sequences are now proposed to contribute to genome integrity. Despite their potential impact on the architecture and evolution of the genome, satellite DNAs have not been investigated in oomycetes due to the paucity of genomic data and the difficulty of assembling highly conserved satellite arrays. Yet gaining knowledge on the structure and evolution of genomes of oomycete pathogens is crucial to understanding the mechanisms underlying adaptation to their environment and to proposing efficient disease control strategies. A assembly of the genome of , an important oomycete plant pathogen, led to the identification of several families of tandemly repeated sequences varying in size, copy number, and sequence conservation. Among them, two abundant families, designated as and , displayed typical features of satellite DNA and were collectively designated as . These two satellite families differ by their length, sequence, organization, genomic environment, and evolutionary dynamics. , but not , presented homologs among oomycetes. This observation, as well as the characterization of transcripts of families, suggested that these satellite DNA families likely play a conserved role within this important group of pathogens.