Service Communautaire d'Information sur la Recherche et le Développement - CORDIS

FP7

CAARL Report Summary

Project reference: 331450
Funded under: FP7-PEOPLE

Periodic Report Summary 1 - CAARL (Comparative Genomics and Environmental Diversity of Coral Associated Apicomplexa-Related Lineages)

Coral reefs are home to the greatest density of species in shallow marine waters, including diverse microbial communities. However, almost everything we know about reef microbial communities is confined to prokaryotes and viruses: next to nothing is known about the microbial eukaryotes (protists), with the exception of Symbiodinium. Symbiodinium (a dinoflagellate) forms an endosymbiotic interaction with coral that is critical to reef health: coral bleaching is the stress-related expulsion of Symbiodinium, and is a global threat to reef diversity. Beyond Symbiodinium, we know little about reef protist communities, how they interact with corals and other microbes, or the interplay between protists, environmental gradients, and coral health.
The interest in reef protists began with the discoveries of Chromera and Vitrella. These two reef-associated algae are assumed to form a symbiotic relationship similar to that of Symbiodinium. However, nearly all work to date has focused on their phylogeny. As photosynthetic relatives of apicomplexan parasites, they held answers to long-debated questions about plastid evolution, but equally important questions about their functional relationship to corals and the reef community have hardly been asked. To address these questions, an ecological approach was needed, and preliminary work in this direction revealed unexpected opportunities. Using plastid 16S data, it was showed that apicomplexan-related lineages (ARLs) are the richest source of still-unidentified plastid diversity, and that virtually all of this diversity is restricted to coral reefs. We now know they exist, but have no direct information on their biology or role in reef ecosystems whatsoever.
We are focusing our research on two questions:

What is the protist diversity on coral reefs? In order to answer this question we have been working with coral samples retrieved from Northern Line Islands. We have developed a pilot study with a limited number of samples in order to evaluate the feasibility of using 18S rDNA V4 region amplicon sequences using pan-eukaryotic primers for Illumnia MiSeq to determine the protist diversity. In this first pilot study we have observe three crucial things for the future development of the project: 1) the 18S signal retrieved from the cnidarian (the coral) is not as high as expected 2) the signal from Symbiodinimum dominates widely our dataset and shows a relatively high diversity among the group 3) we can also can retrieve the signal of less abundant protist and these appear in similar patterns in different coral samples. These protists probably represent endemic population associated to corals but this point needs further analysis to be corroborated.

As another aspect of this question we have also been working with a relevant protist isolated from corals, the alga Ostreobium. Ostreobium is a green alga that is known to be associated to corals but is still unclear if its role is beneficiary or pernicious to the animal. We have been able to retrieve its 18S rDNA sequence and its chloroplast genome. We are almost done with the analysis of the diversity ond distribuition of this alga in different coral systems as well as generating the first 18S phylogeny for this organism and the analysis of its chloroplast genome.

What is the relationship between apicomplexan relatives and corals? Before going deeper in the analysis of the relationship of the apicomplexans relatives with corals we needed to create a reliable phylogenetic framework for the analysis of 18S amplicons. It has never been done for the apicomplexans so the first thing we have done has been a meta-analysis of all the available 18S rDNA sequences for the apicomplexans and their related lineages. As a result from the analysis of up to 10,000 sequences we have been able to produce a high quality phylogenetic tree for the apicomplexans and related lineages as well as a reference dataset combining sequences, taxonomic information and different kinds of metadata.

Our firsts steps are leading us on the good direction. Our success setting up all the methodology to use high-throughput sequencing (HTS) for the analysis of the eukaryotic population associated to corals will allow us to start processing a higher amounts of samples. Then we will be able to analyse the distribution of these population across different gradients like human activity impact over corals or light gradients. Also our work on Ostreobium will help to characterize an organism that can potentially have a huge impact (either positive or negative) on the preservation of the coral reef ecosystems.

The development of a reference database for apicomplexans will be extremely useful not only for our own project, being the phylogenetic map we need to finally identify the ARL, but also for the community. Considering the emergence of the use of HTS techniques, not only in ecology but also in biomedical/biotechnological studies, having a reference dataset for a group of widespread parasites, as the apicomplexans, can be useful for diagnosis, characterization and epidemiology.

Contact

Sereno Alvarez, Alberto (Financial Officer)
Tel.: +34 91 5668852
Fax: +34 91 5668913
E-mail

Subjects

Life Sciences
Record Number: 182171 / Last updated on: 2016-05-24
Information source: SESAM