Insights into the transcriptional and translational mechanisms of linear organellar chromosomes in the box jellyfish Alatina alata (Cnidaria: Medusozoa: Cubozoa)

The Highly Divergent Mitochondrial Genomes Indicate That the Booklouse, Liposcelis bostrychophila (Psocoptera: Liposcelididae) Is a Cryptic Species

The booklouse, Liposcelis bostrychophila is an important storage pest worldwide. The mitochondrial (mt) genome of an asexual strain (Beibei, China) of the L. bostrychophila comprises two chromosomes; each chromosome contains approximate half of the 37 genes typically found in bilateral animals. The mt genomes of two sexual strains of L. bostrychophila, however, comprise five and seven chromosomes, respectively; each chromosome contains one to six genes. To understand mt genome evolution in L. bostrychophila, and whether L. bostrychophila is a cryptic species, we sequenced the mt genomes of six strains of asexual L. bostrychophila collected from different locations in China, Croatia, and the United States. The mt genomes of all six asexual strains of L. bostrychophila have two chromosomes. Phylogenetic analysis of mt genome sequences divided nine strains of L. bostrychophila into four groups. Each group has a distinct mt genome organization and substantial sequence divergence (48.7–87.4%) from other groups. Furthermore, the seven asexual strains of L. bostrychophila, including the published Beibei strain, are more closely related to two other species of booklice, L. paeta and L. sculptilimacula, than to the sexual strains of L. bostrychophila. Our results revealed highly divergent mt genomes in the booklouse, L. bostrychophila, and indicate that L. bostrychophila is a cryptic species.

Circular RNAs: Regulators of Cancer-Related Signaling Pathways and Potential Diagnostic Biomarkers for Human Cancers

Circular RNAs (circRNAs) are newly discovered endogenous non-coding RNAs featuring structural stability, high abundance, and tissue-specific expression. CircRNAs are prevalent and conserved in mammalian cells. They are involved in cellular processes and regulate gene expression at the transcriptional or post-transcriptional level by interacting with microRNAs (miRNAs) and other molecules. Recent studies have shown that circRNAs play an important role in the progression of various human diseases including atherosclerosis, nervous system disorders, diabetes, and cancer. In this review, we summarize the advances on endogenous circRNAs in eukaryotic cells and elucidate their diagnostic and prognostic significance in human cancers. Especially, we highlight the involvement of circRNAs in signal transduction pathways as well as their clinical potential to serve as biomarkers.

Mitochondrial RNA processing in absence of tRNA punctuations in octocorals

BACKGROUND

Mitogenome diversity is staggering among early branching animals with respect to size, gene density, content and order, and number of tRNA genes, especially in cnidarians. This last point is of special interest as tRNA cleavage drives the maturation of mitochondrial mRNAs and is a primary mechanism for mt-RNA processing in animals. Mitochondrial RNA processing in non-bilaterian metazoans, some of which possess a single tRNA gene in their mitogenomes, is essentially unstudied despite its importance in understanding the evolution of mitochondrial transcription in animals.

RESULTS

We characterized the mature mitochondrial mRNA transcripts in a species of the octocoral genus Sinularia (Alcyoniidae: Octocorallia), and defined precise boundaries of transcription units using different molecular methods. Most mt-mRNAs were polycistronic units containing two or three genes and 5' and/or 3' untranslated regions of varied length. The octocoral specific, mtDNA-encoded mismatch repair gene, the mtMutS, was found to undergo alternative polyadenylation, and exhibited differential expression of alternate transcripts suggesting a unique regulatory mechanism for this gene. In addition, a long noncoding RNA complementary to the ATP6 gene (lncATP6) potentially involved in antisense regulation was detected.

CONCLUSIONS

Mt-mRNA processing in octocorals possessing a single mt-tRNA is complex. Considering the variety of mitogenome arrangements known in cnidarians, and in general among non-bilaterian metazoans, our findings provide a first glimpse into the complex mtDNA transcription, mt-mRNA processing, and regulation among early branching animals and represent a first step towards understanding its functional and evolutionary implications.