Biology subjects

Kroiher, M.

Publications and source records attributed to Kroiher, M..

3 recordsLinked to original sources

bioRxiv2022

CRISPR/Cas9 mediated gene editing in non-model nematode Panagrolaimus sp. PS1159

The phylum Nematoda harbors a huge diversity of species in a broad range of ecosystems and habitats. Nematodes share a largely conserved Bauplan but major differences have been found in early developmental processes. The development of the nematode model organism Caenorhabditis elegans has been studied in great detail for decades. These efforts have provided the community with a large number of protocols and methods. Unfortunately, many of these tools are not easily applicable in non-Caenorhabditis nematodes. In recent years it has become clear that many crucial genes in the C. elegans developmental toolkit are absent in other nematode species. It is thus necessary to study the developmental program of other nematode species in detail to understand evolutionary conservation and novelty in the phylum. Panagrolaimus sp. PS1159 is a non-parasitic nematode exhibiting parthenogenetic reproduction and we are establishing the species to comparatively study evolution, biodiversity and alternative reproduction and survival strategies. Here, we demonstrate the first successful application of the CRISPR/Cas9 system for genome editing in Panagrolaimus sp. PS1159 and its closely related hermaphroditic species Propanagrolaimus sp. JU765 with both the non-homologous end joining and the homology-directed repair mechanism. Using microinjections and modifying published protocols from C. elegans and P. pacificus we induced mutations in the orthologue of unc-22, which resulted in a visible uncoordinated twitching phenotype. We also compared the HDR efficiency following the delivery of different repair templates. This work will expand the applicability for a wide range of non-model nematodes from across the tree and facilitate functional analysis into the evolution of parthenogenesis, changes in the developmental program of Nematoda, and cryptobiosis.

molecular biology↗

bioRxiv2017

Differences in the genetic control of early egg development and reproduction between C. elegans and its parthenogenetic relative D. coronatus

BackgroundThe free-living nematode Diploscapter coronatus is the closest known relative of C. elegans with parthenogenetic reproduction. It shows several developmental idiosyncracies, for example concerning the control of meiosis and embryonic axis formation [1]. Our recent genome analysis [2] provided some support for the view that D. coronatus is a product of interspecies hybridization. Here we present additional data towards this assumption. Based on genomic and transcriptomic data we try to better understand the molecular basis of developmental idiosyncrasies in this species in an evolutionary context by comparison with selected other nematodes.\n\nResultsIn a genomic comparison between D. coronatus, C. elegans, other representatives of the genus Caenorhabditis and the more distantly related Pristionchus pacificus and Panagrellus redivivus, certain genes required for normal embryogenesis in C. elegans were found to be restricted to the genus Caenorhabditis. The mRNA content of early D. coronatus embryos was sequenced and compared with similar stages in C. elegans and Ascaris suum. We identified 350 gene families transcribed in the early embryo of D. coronatus but not in the other two nematodes. Looking at individual genes transcribed early in D. coronatus but not in C. elegans and A. suum we found that orthologs of most of these are present in the genomes of the latter species as well, suggesting heterochronic shifts with respect to expression behavior. Considerable divergence between alleles lends further support to the view that D. coronatus may be the result of an interspecies hybridization. Expression analysis of early acting single copy genes yield no indication for silencing of one parental genome.\n\nConclusionsOur comparative cellular and molecular studies support the view that the genus Caenorhabditis differs considerably from the other studied nematodes in its control of development and reproduction. The easy-to-culture parthenogenetic D. coronatus, with its high quality draft genome and only a single chromosome when haploid, offers many new starting points on the cellular, molecular, and genomic level to better understand alternative routes of nematode development and reproduction.

evolutionary biology↗

bioRxiv2017

Signatures of the evolution of parthenogenesis and cryptobiosis in the genomes of panagrolaimid nematodes

Most animal species reproduce sexually, but parthenogenesis, asexual reproduction of various forms, has arisen repeatedly. Parthenogenetic lineages are usually short lived in evolution; though in some environments parthenogenesis may be advantageous, avoiding the cost of sex. Panagrolaimus nematodes have colonised environments ranging from arid deserts to arctic and antarctic biomes. Many are parthenogenetic, and most have cryptobiotic abilities, being able to survive repeated complete desiccation and freezing. It is not clear which genomic and molecular mechanisms led to the successful establishment of parthenogenesis and the evolution of cryptobiosis in animals in general. At the same time, model systems to study these traits in the laboratory are missing.\n\nWe compared the genomes and transcriptomes of parthenogenetic and sexual Panagrolaimus able to survive crybtobiosis, as well as a non-cryptobiotic Propanogrolaimus species, to identify systems that contribute to these striking abilities. The parthenogens are most probably tripoids originating from hybridisation (allopolyploids). We identified genomic singularities like expansion of gene families, and selection on genes that could be linked to the adaptation to cryptobiosis. All Panagrolaimus have acquired genes through horizontal transfer, some of which are likely to contribute to cryptobiosis. Many genes acting in C. elegans reproduction and development were absent in distant nematode species (including the Panagrolaimids), suggesting molecular pathways cannot directly be transferred from the model system.\n\nThe easily cultured Panagrolaimus nematodes offer a system to study developmental diversity in Nematoda, the molecular evolution of parthenogens, the effects of triploidy on genomes stability, and the origin and biology of cryptobiosis.

evolutionary biology↗