Mlig-SKP1 Gene Is Required for Spermatogenesis in the Flatworm Macrostomum lignano

In a free-living flatworm, Macrostomum lignano, an S-phase kinase-associated protein 1 (SKP1) homologous gene was identified as enriched in proliferating cells, suggesting that it can function in the regulation of stem cells or germline cells since these are the only two types of proliferating cells in flatworms. SKP1 is a conserved protein that plays a role in ubiquitination processes as a part of the Skp1-Cullin 1-F-box (SCF) ubiquitin ligase complex. However, the exact role of Mlig-SKP1 in M. lignano was not established. Here, we demonstrate that Mlig-SKP1 is neither involved in stem cell regulation during homeostasis, nor in regeneration, but is required for spermatogenesis. Mlig-SKP1(RNAi) animals have increased testes size and decreased fertility as a result of the aberrant maturation of sperm cells. Our findings reinforce the role of ubiquitination pathways in germ cell regulation and demonstrate the conserved role of SKP1 in spermatogenesis.

Proof of principle for piggyBac-mediated transgenesis in the flatworm Macrostomum lignano

Regeneration-capable flatworms are informative research models to study the mechanisms of stem cell regulation, regeneration, and tissue patterning. The free-living flatworm Macrostomum lignano is currently the only flatworm where stable transgenesis is available, and as such it offers a powerful experimental platform to address questions that were previously difficult to answer. The published transgenesis approach relies on random integration of DNA constructs into the genome. Despite its efficiency, there is room and need for further improvement and diversification of transgenesis methods in M. lignano. Transposon-mediated transgenesis is an alternative approach, enabling easy mapping of the integration sites and the possibility of insertional mutagenesis studies. Here, we report for the first time that transposon-mediated transgenesis using piggyBac can be performed in M. lignano to create stable transgenic lines with single-copy transgene insertions.

Diversity of <i>mariner</i>-like elements in Orthoptera

Mariner-like elements (MLEs) are among the most widespread DNA transposable elements in eukaryotes. Insects were the first organisms in which MLEs were identified, however the diversity of MLEs in the insect order Orthoptera has not yet been addressed. In the present study, we explore the diversity of MLEs elements in 16 species of Orthoptera belonging to three infraorders, Acridoidea (Caelifera), Grylloidea (Ensifera), and Tettigoniidea (Ensifera) by combining data mined from computational analysis of sequenced degenerative PCR MLE amplicons and available Orthoptera genomic scaffolds. In total, 75 MLE lineages (Ortmar) were identified in all the studied genomes. Automatic phylogeny-based classification suggested that the current known variability of MLEs can be assigned to seven statistically well-supported phylogenetic clusters (I–VII), and the identified Orthoptera lineages were distributed among all of them. The majority of the lineages (36 out of 75) belong to cluster I; 20 belong to cluster VI; and seven, six, four, one and one lineages belong to clusters II, IV, VII, III, and V, respectively. Two of the clusters (II and IV) were composed of a single Orthoptera MLE lineage each (Ortmar37 and Ortmar45, respectively) which were distributed in the vast majority of the studied Orthoptera genomes. Finally, for 16 Orthoptera MLE lineages, horizontal transfer from the distantly related taxa belonging to other insect orders may have occurred. We believe that our study can serve as a basis for future researches on the diversity, distribution, and evolution of MLEs in species of other taxa that are still lacking the sequenced genomes.

The Evaluation of Genetic Relationships within Acridid Grasshoppers (Orthoptera, Caelifera, Acrididae) on the Subfamily Level Using Molecular Markers

Over the last few decades, molecular markers have been extensively used to study phylogeny, population dynamics, and genome mapping in insects and other taxa. Phylogenetic methods using DNA markers are inexpensive, fast and simple to use, and may help greatly to resolve phylogenetic relationships in groups with problematic taxonomy. However, different markers have various levels of phylogenetic resolution, and it's important to choose the right set of molecular markers for a studied taxonomy level. Acrididae is the most diverse family of grasshoppers. Many attempts to resolve the phylogenetic relationships within it did not result in a clear picture, partially because of the limited number of molecular markers used. We have tested a phylogenetic resolution of three sets of the most commonly utilized mitochondrial molecular markers available for Acrididae sequences in the database: (i) complete protein-coding mitochondrial sequences, (ii) concatenated mitochondrial genes COI, COII, and Cytb, and (iii) concatenated mitochondrial genes COI and COII. We then complemented the analysis by testing the nuclear ITS2 region. Adequate phylogenetic resolution of Acrididae subfamilies can be achieved using three (COI, COII, and Cytb) or more mitochondrial markers. Moreover, we found the ITS2 and concatenated COI/COII markers to be the least informative, providing a poor resolution. All the studied acridids fall into three well-supported phylogenetic groups that include 13 subfamilies. Acridinae, Gomphocerinae, Oedipodinae, and Catantopinae are shown to be polyphyletic, while the remaining subfamilies are in accordance with current Acrididae systematics. Our study provides a basis for more comprehensive phylogenetic analyses of Acrididae on the subfamily and lower levels.