SymbioticHydraexpress a plant-like peroxidase gene during oogenesis

Abstract

SUMMARY Symbiotic associations accompanied by gene exchange between the symbionts form the phylogenetic origin of eukaryotic cells and, therefore, had significant impact on species diversity and evolutionary novelty. Among the phylogenetically oldest metazoan animals known to form symbiotic relationships are the Cnidaria. In the Cnidarian Hydra viridis, symbiotic algae of the genus Chlorella are located in endodermal epithelial cells and impact sexual differentiation. When screening for Hydra viridis genes that are differentially expressed during symbiosis, we found a gene, HvAPX1, coding for a plant-related ascorbate peroxidase. HvAPX1 is expressed exclusively during oogenesis and in contrast to all known ascorbate peroxidase genes in plants does not contain introns. No member of this gene family has previously been identified from a member of the animal kingdom. We discuss the origin of the HvAPX1 gene and propose that it may have been transferred horizontally following an endosymbiotic event early in evolution of the Hydra lineage as an RNA or cDNA intermediate.

Enzymes of the shikimic acid pathway encoded in the genome of a basal metazoan, Nematostella vectensis , have microbial origins

“…Comparative genomic examination of glyoxylate cycle enzymes has revealed the likely transfer of a bifunctional isocitrate lyase (ICL) and a MS, encoded by a fused ICL-MS gene from a bacterial precursor, to the N. vectensis genome (27). Our findings are similar to those of others reporting evidence of gene transfer to freshwater cnidarian (Hydra) species from multiple ancestral eukaryotic partners (18,28).…”

Alternative oxidase in animals: unique characteristics and taxonomic distribution

“…We determined that the AOX sequence from the animal Hydra magnipapillata Ito is not of animal origin but appears to be from a higher plant source. This may represent a horizontal gene transfer event from a symbiont to the Hydra as was recently proposed for a plant-like peroxidase gene (Habetha and Bosch, 2005). It may also be the result of contamination of the animal sample with external material during collection or processing and illustrates the need for caution when interpreting data collected from public databases.…”

Value of the Hydra model system for studying symbiosis

“…3) (Douglas, 1994). However up to recently the general idea was that it was not possible to successfully achieve the permanent and stable culture of endosymbionts independently from green Hydra as it is the case for free-living relatives (McAuley and Smith, 1982;Rahat, 1992;Huss et al, 1993Huss et al, /1994Friedl, 1997;Habetha and Bosch, 2005). But recently different species of endosymbionts have been isolated from green Hydra and cultured on the long term (Fig.…”

“…Genes acquired through HGT are transcribed and transferred to the offspring (Pierce et al, 2007). As a convincing evidence, Hydra viridissima acquired a plant-like ascorbate peroxidase that does not have any cognate gene in the animal kingdom but is expressed in the digestive cells and in the oocyte (Habetha and Bosch, 2005). Similarly in the green sea slug Elysia chlorotica that forms a symbiotic relationship with algal chloroplasts, algal nuclear genes involved in photosynthesis were identified in the host cell genome (Rumpho et al, 2008).…”

“…Although symbiosis in green Hydra attracted the interest of researchers since long ago, little is known about the molecular basis of survival of endosymbiotic algae and about the mechanisms controling the interactions between both partners (Habetha and Bosch, 2005). Why some Hydra species can, when other species cannot form an endosymbiotic relationship with the unicellular algae?…”