MYXOZOA EVO DEVO

Evolution and development in Myxozoa: body-plan simplification associated with endoparasitism

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 Obiettivo del progetto (Objective)

'Myxozoa are endoparasitic animals that exploit invertebrates and fish. Their phylogenetic position has long been controversial. However, recent placement within Cnidaria makes it clear that myxozoans have undergone astonishing morphological simplification associated with the evolution of parasitism. Such simplification is characteristic of many parasites but the genetic and developmental bases are poorly understood. Myxozoa demonstrate perhaps the most extreme example of simplification known to date, lacking a nervous system, gonads, cilia and centrioles. Differing degrees of simplification within the group provide an ideal opportunity to investigate the genetic and developmental bases of morphological simplification in a comparative approach. The myxozoan Buddenbrockia plumatellae forms muscular worms with a polarised body plan while the very closely related Tetracapsuloides bryosalmonae occurs as simple, unpolarised sacs. This fellowship proposes to generate transcriptomes of developmental stages from these two species by next-generation sequencing. Resulting data will be used to (i) compare developmental gene repertoires and expression levels of the two species and (ii) identify how myxozoans are related to other cnidarians. In a second step, expression patterns of developmental genes will be analysed by in situ hybridization. A third step will characterise the morphology and ultrastructure in regions of gene expression. Collectively, these investigations will provide a comprehensive picture of myxozoan development that can be compared to patterns in other myxozoans and free-living cnidarians. The research will (i) produce novel insights about morphological simplification associated with parasitism (ii) advance our understanding of a previously unrecognized radiation of endoparasitic cnidarians and (iii) provide training in cutting-edge techniques that will add to the candidate’s toolkit and career development.'

Introduzione (Teaser)

Parasite evolution is often associated with significant simplification of body structures (morphology). A new study has shed light on poorly understood genetic mechanisms.

Descrizione progetto (Article)

EU-funded scientists took the Myxozoa, among the most extremely simplified parasites, as a model system to study developmental genetics for novel insight and enhanced understanding. The project 'Evolution and development in Myxozoa: body-plan simplification associated with endoparasitism' (MYXOZOA EVO DEVO) is the first detailed analysis of developmental processes in Myxozoa.

It compared two closely related myxozoan species on the evolutionary branch represented by the Malacosporea. One has extremely simplified morphology evident as a large immotile sac lined with a single epithelial tissue layer. The other is worm-like with longitudinal muscle between two epithelial layers imparting the capacity for locomotion.

Scientists carried out extensive field work to collect and culture infected host organisms. This allowed them to obtain the required tissue material containing RNA for generating transcriptomes (libraries of nearly all the genes expressed in an organism). Researchers exploited next-generation sequencing, an advanced method producing a greatly expanded range of sequences to study these non-model organisms.

The organisms produced transcripts related to neurotransmission suggesting that, despite the lack of obvious nervous system structures, some form of neurotransmission likely occurs. The neurons, like the organisms as a whole, appear to have simplified structures compared to those of higher organisms. Most genes used by higher organisms for patterning of body-plan elements or body structures exist and are expressed, although at very low levels. Continued research should elucidate how they are used.

Given recent evidence that myxozoans evolved from free-living cnidarians, it was also of interest to compare subcellular organelles in these two organisms. Scientists found highly significant similarities in proteins associated with myxozoan and cnidarian organelles thought to be homologous, supporting that hypothesis.

The database will be made publicly available, serving as an invaluable resource for researchers in the field. Manuscripts are in preparation and results have already been presented at major international conferences. MYXOZOA EVO DEVO has made an important contribution to evolutionary developmental biology with enhanced insight into the evolution of parasitism in lower animals. In recognition, the team was invited by Springer Publishers to develop the first book ever on Myxozoa.