Conservative route to genome compaction in a miniature annelid

Abstract

The causes and consequences of genome reduction in animals are unclear because our understanding of this process mostly relies on lineages with often exceptionally high rates of evolution. Here, we decode the compact 73.8-megabase genome of Dimorphilus gyrociliatus, a meiobenthic segmented worm. The D. gyrociliatus genome retains traits classically associated with larger and slower-evolving genomes, such as an ordered, intact Hox cluster, a generally conserved developmental toolkit and traces of ancestral bilaterian linkage. Unlike some other animals with small genomes, the analysis of the D. gyrociliatus epigenome revealed canonical features of genome regulation, excluding the presence of operons and trans-splicing. Instead, the gene-dense D. gyrociliatus genome presents a divergent Myc pathway, a key physiological regulator of growth, proliferation and genome stability in animals. Altogether, our results uncover a conservative route to genome compaction in annelids, reminiscent of that observed in the vertebrate Takifugu rubripes.

Genomic Signatures Supporting the Symbiosis and Formation of Chitinous Tube in the Deep-Sea Tubeworm Paraescarpia echinospica

“…S3 , Supplementary Material online), correspond to a reduction from 17 chromosomes in ancient bilaterians to 14 pseudochromosomes in P. echinospica . Conserved ALGs can be found in C. teleta ( Simakov et al 2013 ) and D. gyrociliatus ( Martín-Durán et al 2021 ), but completely lost in clitellate annelids Helobdella robusta ( Simakov et al 2013 ) and Eisenia andrei ( supplementary fig. S4 , Supplementary Material online), suggesting a conserved genomic architecture in marine annelids and a large-scale genomic reorganization in Clitellata during the invasion of freshwater and terrestrial habitats.…”

Nemertean, Brachiopod, and Phoronid Neuropeptidomics Reveals Ancestral Spiralian Signaling Systems

“…GPR142 is still an orphan receptor. Protostome receptors of this expanded group are activated by neuropeptides with amidated aromatic C-termini, such as MIP [Wamide] ( Kim et al 2010 ; Conzelmann, Williams, Tunaru, et al 2013; Peymen et al 2019 ), myosuppressin [RFamide] ( Egerod et al 2003 ), RGWamide [Wamide] ( Bauknecht and Jékely 2015 ), P. dumerilii neuropeptide Y-4 [RFamide] ( Bauknecht and Jékely 2015 ), and arthropod FMRFamide [RFamide] ( Cazzamali and Grimmelikhuijzen 2002 ; Meeusen et al 2002 ).…”

“…The endogenous ligands of lophotrochozoan FMRFamide type-1 receptors and ecdysozoan type-2 receptors are also unknown. The FMRFamide type-1 receptor was deorphanized from Drosophila melanogaster and is activated by different FMRFamide-like peptides with the highest sensitivity to endogenous Drosophila FMRFamide peptides ( Cazzamali and Grimmelikhuijzen 2002 ; Meeusen et al 2002 ). In lophotrochozoans, however, FMRFamide activates a completely different receptor ( Bauknecht and Jékely 2015 ; Thiel et al 2017 ), the FMRFamide type-2 receptor (see also fig.…”

Structural and Functional Characterization of the FGF Signaling Pathway in Regeneration of the Polychaete Worm Alitta virens (Annelida, Errantia)

“…The same is true of the protostomian repertoire, which in addition acquired representatives of FGF9/16/20 and probably FGF1/2 subfamilies [ 15 , 16 ]. A complete loss of FGF ligands has been documented in certain annelid lineages [ 41 ].…”

“…The variety of ligands and receptors of the FGF pathway has never been described in detail for any spiralian (lophotrochozoan) animal. The expression of the components of the FGF pathway is shown in embryonic and larval development of brachiopods [ 39 , 40 ], a phoronid [ 40 ] and, partially, in an annelid Capitella teleta [ 41 ].…”