Proteins with tandemly arranged repeats of a highly charged 16-amino-acid motif encoded by the Dhmst101 gene family are structural components of the outer sheath of the extremely elongated sperm tails of Drosophila hydei

The copepod Eurytemora affinis as a relevant species to assess estuarine sediment toxicity: Effects on gene expression and swimming behavior

Compared to freshwater ecosystems, the health status of estuarine waters remains little studied despite their importance for many species. They represent a zone of interest for Human settlements that make them the final sink of pollution in both the water column and sediment. Once in sediments, pollutants could represent a threat to benthic as well as pelagic estuarine species through resuspension events. In the Seine estuary, the copepod Eurytemora affinis has been previously presented as a relevant species to assess resuspended sediment contamination through fitness-related effects at the individual level. The aim of the present study was to use E. affinis copepods to assess estuarine sediment-derived elutriates toxicity at environmental concentrations of particles using a molecular (i.e. transcriptomics) and a behavioral approach. Two sites along the Seine estuary were sampled. The analysis of sediments reveals that both sites have the same granulometric composition and close contamination profiles with the detection of PCBs, PAHs and pyrethroid insecticides. The transcriptomic analysis reveals that exposure to elutriates from both sites triggers the dysregulation of genes involved in biological function as defense response, immunity, ecdysone pathway or neurotoxicity with 66% and 36% of shared genes at the highest concentration for Tancarville and Fatouville. This analysis also reveals a higher count of dysregulated genes in the Fatouville site compared to the Tancarville (271 vs 148) despite their close contamination profile. These results emphasize the molecular approach sensitivity to assess environmental matrix toxicity with E. affinis. The analysis of the swimming behavior of E. affinis did not highlight significant effects after elutriate exposure. However, our strategy to assess E. affinis swimming behavior allows the discrimination of basal swimming behavior i.e. dark/light velocity changes and strong thigmotaxis behavior. Thus, it represents a promising standardized tool to assess copepods swimming behavior in ecotoxicological studies.

The apical annuli of Toxoplasma gondii are composed of coiled-coil and signalling proteins embedded in the inner membrane complex sutures

The apical annuli are among the most intriguing and understudied structures in the cytoskeleton of the apicomplexan parasite Toxoplasma gondii. We mapped the proteome of the annuli in Toxoplasma by reciprocal proximity biotinylation (BioID), and validated five apical annuli proteins (AAP1-5), Centrin2, and an apical annuli methyltransferase. Moreover, inner membrane complex (IMC) suture proteins connecting the alveolar vesicles were also detected and support annuli residence within the sutures. Super-resolution microscopy identified a concentric organisation comprising four rings with diameters ranging from 200 to 400 nm. The high prevalence of domain signatures shared with centrosomal proteins in the AAPs together with Centrin2 suggests that the annuli are related and/or derived from the centrosomes. Phylogenetic analysis revealed that the AAPs are conserved narrowly in coccidian, apicomplexan parasites that multiply by an internal budding mechanism. This suggests a role in replication, for example, to provide pores in the mother IMC permitting exchange of building blocks and waste products. However, presence of multiple signalling domains and proteins are suggestive of additional functions. Knockout of AAP4, the most conserved compound forming the largest ring-like structure, modestly decreased parasite fitness in vitro but had no significant impact on acute virulence in vivo. In conclusion, the apical annuli are composed of coiled-coil and signalling proteins assembled in a pore-like structure crossing the IMC barrier maintained during internal budding.

Identification of tarsal-less peptides from the silkworm Bombyx mori

The polycistronic and non-canonical gene tarsal-less (tal, known as pri) was reported to be required for embryonic and imaginal development in Drosophila; however, there are few reports of the tal gene in the silkworm Bombyx mori. Here, we cloned a tal-like (Bmtal) gene, and a sequence analysis showed that the Bmtal cDNA (1661 bp) contains five small open reading frames (smORFs) (A1, A2, A3, A4, and B) that encode short peptides of 11-12 (A1-A4) amino acid residues containing an LDPTG(E)L(Q)(V)Y motif that is conserved in Drosophila Tal, as well as a 32-amino-acid B peptide. Reverse transcription-quantitative polymerase chain reaction showed that the expression of the Bmtal gene was highest in the trachea, followed by the silk gland and Malpighian tubule, in day 3 fifth-instar larvae. Subcellular localization showed that BmTal localized in the nucleus. By regulating the expression of the full-length Bmtal gene and the functional smORFs of Bmtal, we showed that the expression levels of the Bmovo gene and genes related to the Notch, transforming growth factor-β, and Hippo signaling pathways changed with changes in BmTal peptide expression. A co-immunoprecipitation assay showed that BmTal interacts with polyubiquitin, which triggered degradation and/or processing of the 14-3-3 protein zeta. A comparative transcriptome analysis showed that 2843 (2045) genes were up- (down)-regulated after Bmtal gene expression was up-regulated. The up- (down)-regulated differentially expressed genes were enriched in 326 (278) gene ontology terms (P ≤ 0.05) and 54 (59) Kyoto Encyclopedia of Genes and Genomes pathways (P ≤ 0.05), and the results indicated that the BmTal peptides could function as mediators of hormone levels or the activities of multiple pathways, including the peroxisome proliferator-activated receptor, Hedgehog, mitogen-activated protein kinase, adipocytokine, and gonadotropin-releasing hormone signaling pathways, as well as the innate immune response. These results increase our understanding of the function and mechanism of BmTal at the genome-wide level.

New insights into the cell biology of insect axonemes

Insects do not possess ciliated epithelia, and cilia/flagella are present in the sperm tail and--as modified cilia--in mechano- and chemosensory neurons. The core cytoskeletal component of these organelles, the axoneme, is a microtubule-based structure that has been conserved throughout evolution. However, in insects the sperm axoneme exhibits distinctive structural features; moreover, several insect groups are characterized by an unusual sperm axoneme variability. Besides the abundance of morphological data on insect sperm flagella, most of the available molecular information on the insect axoneme comes from genetic studies on Drosophila spermatogenesis, and only recently other insect species have been proposed as useful models. Here, we review the current knowledge on the cell biology of insect axoneme, including contributions from both Drosophila and other model insects.

A novel sheathed surface organelle of the Helicobacter pylori cag type IV secretion system

Type I strains of Helicobacter pylori (Hp) use a type IV secretion system (T4SS), encoded by the cag pathogenicity island (cag-PAI), to deliver the bacterial protein CagA into eukaryotic cells and to induce interleukin-8 secretion. Translocated CagA is activated by tyrosine phosphorylation involving Src-family kinases. The mechanism and structural basis for type IV protein secretion is not well understood. We describe here, by confocal laser scanning microscopy and field emission scanning electron microscopy, a novel filamentous surface organelle which is part of the Hp T4SS. The organelle is often located at one bacterial pole but can be induced by cell contact also along the lateral side of the bacteria. It consists of a rigid needle, covered focally or completely by HP0527 (Cag7 or CagY), a VirB10-homologous protein. HP0527 is also clustered in the outer membrane. The VirB7-homologous protein HP0532 is found at the base of this organelle. These observations demonstrate for the first time by microscopic techniques a complex T4SS-associated, sheathed surface organelle reminiscent to the needle structures of bacterial type III secretion systems.