MiR-277/4989 regulate transcriptional landscape during juvenile to adult transition in the parasitic helminth Schistosoma mansoni.

Schistosomes are parasitic helminths that cause schistosomiasis, a disease affecting circa 200 million people, primarily in underprivileged regions of the world. Schistosoma mansoni is the most experimentally tractable schistosome species due to its ease of propagation in the laboratory and the high quality of its genome assembly and annotation. Although there is growing interest in microRNAs (miRNAs) in trematodes, little is known about the role these molecules play in the context of developmental processes. We use the completely unaware "miRNA-blind" bioinformatics tool Sylamer to analyse the 3'-UTRs of transcripts differentially expressed between the juvenile and adult stages. We show that the miR-277/4989 family target sequence is the only one significantly enriched in the transition from juvenile to adult worms. Further, we describe a novel miRNA, sma-miR-4989 showing that its proximal genomic location to sma-miR-277 suggests that they form a miRNA cluster, and we propose hairpin folds for both miRNAs compatible with the miRNA pathway. In addition, we found that expression of sma-miR-277/4989 miRNAs are up-regulated in adults while their predicted targets are characterised by significant down-regulation in paired adult worms but remain largely undisturbed in immature "virgin" females. Finally, we show that sma-miR-4989 is expressed in tegumental cells located proximal to the oesophagus gland and also distributed throughout the male worms' body. Our results indicate that sma-miR-277/4989 might play a dominant role in post-transcriptional regulation during development of juvenile worms and suggest an important role in the sexual development of female schistosomes

The repertoire of ICE in prokaryotes underscores the unity, diversity, and ubiquity of conjugation

Horizontal gene transfer shapes the genomes of prokaryotes by allowing rapid acquisition of novel adaptive functions. Conjugation allows the broadest range and the highest gene transfer input per transfer event. While conjugative plasmids have been studied for decades, the number and diversity of integrative conjugative elements (ICE) in prokaryotes remained unknown. We defined a large set of protein profiles of the conjugation machinery to scan over 1,000 genomes of prokaryotes. We found 682 putative conjugative systems among all major phylogenetic clades and showed that ICEs are the most abundant conjugative elements in prokaryotes. Nearly half of the genomes contain a type IV secretion system (T4SS), with larger genomes encoding more conjugative systems. Surprisingly, almost half of the chromosomal T4SS lack co-localized relaxases and, consequently, might be devoted to protein transport instead of conjugation. This class of elements is preponderant among small genomes, is less commonly associated with integrases, and is rarer in plasmids. ICEs and conjugative plasmids in proteobacteria have different preferences for each type of T4SS, but all types exist in both chromosomes and plasmids. Mobilizable elements outnumber self-conjugative elements in both ICEs and plasmids, which suggests an extensive use of T4SS in trans. Our evolutionary analysis indicates that switch of plasmids to and from ICEs were frequent and that extant elements began to differentiate only relatively recently. According to the present results, ICEs are the most abundant conjugative elements in practically all prokaryotic clades and might be far more frequently domesticated into non-conjugative protein transport systems than previously thought. While conjugative plasmids and ICEs have different means of genomic stabilization, their mechanisms of mobility by conjugation show strikingly conserved patterns, arguing for a unitary view of conjugation in shaping the genomes of prokaryotes by horizontal gene transfer

Correction: MiR-277/4989 regulate transcriptional landscape during juvenile to adult transition in the parasitic helminth Schistosoma mansoni.

[This corrects the article DOI: 10.1371/journal.pntd.0005559.]

Sma-miR-277 family predicted targets downregulated in developing female parasites.

<p>Fold change expression (Log₂) of high confidence targets of sma-miR-277 family during the development of male and female worms in two conditions: paired (solid line red) and unpaired (dashed green). Black lines represent the mean expression of genes in paired (solid black line) and unpaired (dashed black line) worms.</p

High confidence targets of the sma-miR-277 family identified with a combined approach (Sylamer, miRanda and TargetScan with conservation).

<p>F = female; M = male.</p

MiRNA target prediction based on both miRNA-unaware and miRNA-guided approaches.

<p>(A) Sylamer enrichment landscape plots for 7mers in male (top) and female (bottom) expression data. The x-axis represents a list of transcripts, ranked from more expressed in juveniles to more expressed in adults. The y-axis represents the significance values acquired for each 7mer at each position in the ranked list of transcripts. Coloured boxes represent the fraction of transcripts significantly (adjusted p-value < 0.01) differentially expressed between juvenile and adult worm as found using DESeq2. These transcripts were subsequently filtered based on the presence of the 7mers TGCATTT or GCATTTA as found by Sylamer. The resulting sets are referred to as Male and Female Sylamer genes. (B) Venn Diagram showing the intersection of Male and Female Sylamer genes with schistosome-conserved miRNA targets as found using TargetScan with conservation + miRanda. The overlap represents transcripts with highly conserved sma-miR-277 target sites across the three <i>Schistosome</i> spp (S. <i>mansoni</i>, <i>S</i>. <i>haematobium</i> and S. <i>japonicum</i>) that are also significantly down regulated during worm development.</p

Sma-miR-4989 is expressed in the cells surrounding the oesophagus and cells of the tegument in adult worms.

<p>Whole mount <i>in situ</i> hybridisation for (A) <i>cathepsin B</i>, (B) sma-miR-124a-3p (<i>124a</i>), and (C) sma-miR-4989. (D) Fluorescence <i>in situ</i> hybridisation showing the colocalization of sma-miR-4989 with four co-expressed tegument-specific mRNAs (<i>calpain</i>, <i>npp-5</i>, <i>annexin</i> and <i>gtp-4</i>). Nuclei are stained with DAPI and shown in blue. Anterior of worms is to the left in A-C. Scale Bars: A-C 100 μm; D 10 μm.</p