AUTHOR=Balzano Sergio , Corre Erwan , Decelle Johan , Sierra Roberto , Wincker Patrick , Da Silva Corinne , Poulain Julie , Pawlowski Jan , Not Fabrice 

TITLE=Transcriptome analyses to investigate symbiotic relationships between marine protists

JOURNAL=Frontiers in Microbiology

VOLUME=6

YEAR=2015

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2015.00098

DOI=10.3389/fmicb.2015.00098

ISSN=1664-302X

ABSTRACT=<p>Rhizaria are an important component of oceanic plankton communities worldwide. A number of species harbor eukaryotic microalgal symbionts, which are horizontally acquired in the environment at each generation. Although these photosymbioses are determinant for Rhizaria ability to thrive in oceanic ecosystems, the mechanisms for symbiotic interactions are unclear. Using high-throughput sequencing technology (i.e., 454), we generated large Expressed Sequence Tag (EST) datasets from four uncultured Rhizaria, an acantharian (<italic>Amphilonche elongata</italic>), two polycystines (<italic>Collozoum</italic> sp. and <italic>Spongosphaera streptacantha</italic>), and one phaeodarian (<italic>Aulacantha scolymantha</italic>). We assessed the main genetic features of the host/symbionts consortium (i.e., the holobiont) transcriptomes and found rRNA sequences affiliated to a wide range of bacteria and protists in all samples, suggesting that diverse microbial communities are associated with the holobionts. A particular focus was then carried out to search for genes potentially involved in symbiotic processes such as the presence of c-type lectins-coding genes, which are proteins that play a role in cell recognition among eukaryotes. Unigenes coding putative c-type lectin domains (CTLD) were found in the species bearing photosynthetic symbionts (<italic>A. elongata, Collozoum</italic> sp., and <italic>S. streptacantha</italic>) but not in the non-symbiotic one (<italic>A. scolymantha</italic>). More particularly, phylogenetic analyses group CTLDs from <italic>A. elongata</italic> and <italic>Collozoum</italic> sp. on a distinct branch from <italic>S. streptacantha</italic> CTLDs, which contained carbohydrate-binding motifs typically observed in other marine photosymbiosis. Our data suggest that similarly to other well-known marine photosymbiosis involving metazoans, the interactions of glycans with c-type lectins is likely involved in modulation of the host/symbiont specific recognition in Radiolaria.</p>