Spiralia is a large, ancient and diverse clade of animals, with a conserved early developmental program but diverse larval and adult morphologies. One trait shared by many spiralians is the presence of ciliary bands used for locomotion and feeding. To learn more about spiralian-specific traits we have examined the expression of 20 genes with protein motifs that are strongly conserved within the Spiralia, but not detectable outside of it. Here, we show that two of these are specifically expressed in the main ciliary band of the mollusc
Cilia biogenesis relies on intraflagellar transport (IFT), a conserved transport mechanism which functions bi-directionally to bring protein complexes to the growing ciliary tip and recycle signaling and transport proteins between the cilium and cell body. In
Here we molecularly characterize the
Thus, the
Differential regulation of gene expression has produced the astonishing diversity of life on Earth. Understanding the origin and evolution of mechanistic innovations for control of gene expression is therefore integral to evolutionary and developmental biology. Cytoplasmic polyadenylation is the biochemical extension of polyadenosine at the 3′-end of cytoplasmic mRNAs. This process regulates the translation of specific maternal transcripts and is mediated by the Cytoplasmic Polyadenylation Element-Binding Protein family (CPEBs). Genes that code for CPEBs are amongst a very few that are present in animals but missing in nonanimal lineages. Whether cytoplasmic polyadenylation is present in non-bilaterian animals (i.e., sponges, ctenophores, placozoans, and cnidarians) remains unknown. We have conducted phylogenetic analyses of CPEBs, and our results show that CPEB1 and CPEB2 subfamilies originated in the animal stem lineage. Our assessment of expression in the sea anemone, Nematostella vectensis (Cnidaria), and the comb jelly, Mnemiopsis leidyi (Ctenophora), demonstrates that maternal expression of CPEB1 and the catalytic subunit of the cytoplasmic polyadenylation machinery (GLD2) is an ancient feature that is conserved across animals. Furthermore, our measurements of poly(A)-tail elongation reveal that key targets of cytoplasmic polyadenylation are shared between vertebrates, cnidarians, and ctenophores, indicating that this mechanism orchestrates a regulatory network that is conserved throughout animal evolution. We postulate that cytoplasmic polyadenylation through CPEBs was a fundamental innovation that contributed to animal evolution from unicellular life.
To identify proteins specific to the proximal ciliary axoneme, we used iTRAQ to compare short (~2 μm) and full‐length (~11 μm) axonemes of
The nonfeeding planktonic larvae of marine invertebrates typically lack larval feeding structures. One puzzling exception to this generalization is the annelid clade Sabellidae, in which nonfeeding larvae possess ciliary bands (specifically, food groove and metatroch) that, to the best of our knowledge, have no function other than in feeding. Nishi and Yamasu (1992b,
Dinoflagellates are a diverse group of phytoplankton, ranging from harmful bloom-forming microalgae to photosymbionts of coral reefs. Genome-scale data from dinoflagellates reveal atypical genomic features, extensive genomic divergence, and lineage-specific innovation of gene functions. Long non-coding RNAs (lncRNAs), known to regulate gene expression in eukaryotes, are largely unexplored in dinoflagellates. Here, using high-quality genome and transcriptome data, we identified 48039 polyadenylated lncRNAs in three dinoflagellate species: the coral symbionts Cladocopium proliferum and Durusdinium trenchii, and the bloom-forming species, Prorocentrum cordatum. These lncRNAs have fewer introns and lower G+C content than protein-coding sequences; 37 768 (78.6%) are unique with respect to sequence similarity. We classified all lncRNAs based on conserved motifs (k-mers) into distinct clusters, following properties of protein-binding and/or subcellular localisation. Interestingly, 3708 (7.7%) lncRNAs are differentially expressed under heat stress, algal lifestyle, and/or growth phase, and share co-expression patterns with protein-coding genes. Based on inferred triplex interactions between lncRNA and putative promoter regions, we identified 19 460 putative gene targets for 3721 lncRNAs; 907 genes exhibit differential expression under heat stress. These results reveal, for the first time, the diversity of lncRNAs in dinoflagellates and how lncRNAs may regulate gene expression as a heat-stress response in these ecologically important microbes.
