Mapping of Hieracium (Asteraceae) chromosomes with genus-specific satDNA elements derived from next-generation sequencing data

Abstract

The highly repetitive DNA fraction of the eukaryotic genome is considered a mobile, rapidly changing entity, thus reflecting trajectories of short-term evolutionary change. It consists of several large classes in which transposable elements and satellite DNA (satDNA) predominate. Despite a growing awareness of its structure and functional significance, the evolutionary dynamics of repetitive elements and, particularly, satDNA remain poorly characterized. Next-generation sequencing (NGS) has opened up new possibilities for high-throughput genome analysis. Here, we applied satDNA repeatome elements derived from NGS data as probes for fluorescence in situ hybridization to characterize the karyotypes of three diploid hawkweed species of the predominantly polyploid apomictic genus Hieracium, namely H. intybaceum, H. prenanthoides and H. alpinum. Three cluster-distributed, genus-specific satDNA elements that are not present in the sister genus Pilosella were identified; notably, one element spans the functional centromeres. Each of the investigated diploids possessed a species-specific assortment of detected repeats. Their utilization as molecular-cytogenetic markers, in combination with ribosomal DNA loci, allowed for the development of a system to identify the individual chromosomes of the Hieracium species, thus providing a basis for the future investigation of karyotype evolution in diploid hawkweeds and for exploring satDNA dynamics in hybrids and apomicts of allopolyploid origin.