Abstract
Draft genome sequences of non-bilaterian species have provided important insights into the evolution of the metazoan gene repertoire. However, there is little information about the evolution of gene clusters, genome architectures and karyotypes during animal evolution. Here we report chromosome-level genome assemblies of two related anthozoan cnidarians, the sea anemones, Nematostella vectensis and Scolanthus callimorphus. We find a robust set of 15 chromosomes with a clear one-to-one correspondence of the chromosomes between the two species. We show that, in contrast to Bilateria, Hox and NK clusters of investigated cnidarians are disintegrated, indicating that microsynteny conservation is largely lost. In line with that, we find no evidence for topologically associated domains, suggesting fundamental difference in long-range gene regulation compared to vertebrates. However, both sea anemone genomes show remarkable chromosomal conservation with other cnidarians, several bilaterians and the sponge Ephydatia muelleri, allowing us to reconstruct the putative cnidarian and metazoan chromosomes, consisting of 19 and 16 ancestral linkage groups, respectively. These data suggest that large parts of the ancestral metazoan genome have been retained in chromosomes of some extant lineages, yet, higher order gene regulation may have evolved only after the cnidarian-bilaterian split.
Macrosynteny analysis between Lentinula edodes and Lentinula novae-zelandiae reveals signals of domestication in Lentinula edodes
