The differential expression of ribosomal 18S RNA paralog genes from the chaetognath Spadella cephaloptera

Abstract

Chaetognaths constitute a small marine phylum of approximately 120 species. Two classes of both 18S and 28S rRNA gene sequences have been evidenced in this phylum, even though significant intraindividual variation in the sequences of rRNA genes is unusual in animal genomes. These observations led to the hypothesis that this unusual genetic characteristic could play one or more physiological role(s). Using in situ hybridization on the frontal sections of the chaetognath Spadella cephaloptera, we found that the 18S Class I genes are expressed in the whole body, with a strong expression throughout the gut epithelium, whereas the expression of the 18S Class II genes is restricted to the oocytes. Our results could suggest that the paralog products of the 18S Class I genes are probably the "housekeeping" 18S rRNAs, whereas those of class II would only be essential in specific tissues. These results provide support for the idea that each type of 18S paralog is important for specific cellular functions and is under the control of selective factors.Brought to you by | MIT Libraries Authenticated Download Date | 5/12/18 8:10 PM

Translational machinery of the chaetognath Spadella cephaloptera: a transcriptomic approach to the analysis of cytosolic ribosomal protein genes and their expression

“…Surprisingly, chaetognaths exhibit numerous molecular analogies with plants; two classes of paralogs of 18S-28S rRNA have been reported [ 32 , 33 ], which could be the result of an allopolyploid event in the ancestor of all the extant chaetognaths [ 34 ]. Moreover, in S. cephaloptera , one of the 18S class plays a ubiquitous role whereas the other is specific to oocytes [ 54 ]. The great number of RP paralogs in this species could be the result of the allopolyploidy and we hypothesize that two populations of ribosome could exist in chaetognath cells; one of them contains the housekeeping rRNA (Class I) and the isoforms for which numerous mRNA have been found in the EST database and which give relatively short branches in phylogenetic reconstructions (data not shown); the other contains the class II rRNAs with the other isoforms.…”

Detection of post-F1 fish hybrids in broodstock using molecular markers: approaches for genetic management in aquaculture

“…Sequences of nuclear genes encoding elongation factor 1‐alpha (EF1α), β‐globin (GLOB) and ribosomal RNA 18S (rRNA 18S) (GenBank accession numbers to ) were obtained using the primer pairs described in the Table . The application of the rRNA 18S gene can have some limitations for species identification, because this gene family shows a complex organization with the presence of paralogous copies in the genome of some species (Carranza, Baguñà & Riutort ; Barthélémy, Grino, Pontarotti, Casanova & Faure ). However, we did not detect rDNA 18S variants or alleles within the same species, allowing the precise identification of the Pseudoplatystoma species.…”

Highly divergent 18S rRNA gene paralogs in a Cryptosporidium genotype from eastern chipmunks (Tamias striatus)

“…The sequence homogeneity among 18S rDNA copies that results from concerted evolution is necessary to accurately infer phylogenetic relationships. Some genomes have divergent 18S rDNA copies distributed across multiple chromosomes (Barthelemy et al, 2007; Gunderson et al, 1987; Krieger and Fuerst, 2002). Most notably, divergent 18S rDNA copies in the apicomplexan Plasmodium share only 89–95% sequence similarity (Qari et al, 1994).…”