The Evolutionary Relationships between Endosymbiotic Green Algae of <I>Paramecium bursaria</I> Syngens Originating from Different Geographical Locations

Abstract

Paramecium bursaria (EHRENBERG 1831), a freshwater ciliate, typically harbors hundreds of green algal symbionts inside the cell. The aim of present study was the molecular identification of newly analyzed P. bursaria symbionts. The second aspect of the present survey was testing a hypothesis whether endosymbionts prefer the specified syngen of the host, and the specified geographical distribution. Ten strains of endosymbionts isolated from strains of P. bursaria originating from different geographical locations were studied. We analyzed for the first time, both the fragment of plastid genome containing 3'rpl36-5'infA genes and a fragment of a nuclear gene encoding large subunit ribosomal RNA (LSU rDNA). The analysis of the LSU rDNA sequences showed the existence of 3 haplotypes and the haplotype diversity of 0.733, and 8 haplotypes for the 3'rpl36-5'infA gene fragment and haplotype diversity of 0.956. The endosymbionts isolated from P. bursaria strains were identified as Chlorella vulgaris, Ch. variabilis and Micractinium conductrix. There was no correlation between the syngen of P. bursaria and the species of endosymbiont.

Characterisation of the RNA-interference pathway as a Tool for Genetics in the Nascent Phototrophic Endosymbiosis,Paramecium bursaria

“…In order to investigate the genetic basis of an emergent endosymbiotic system, we must develop experimentally tractable endosymbiotic model species [5][6][7] . Paramecium bursaria is a ciliate protist which harbours several hundred cells of the green algae, Chlorella spp., in a nascent facultative photo-endosymbiosis [8][9][10][11][12] . The algae provide sugar and oxygen derived from photosynthesis, in exchange for amino acids, CO2, divalent cations, and protection from viruses and predators 5,6,[13][14][15][16][17][18][19] .…”

Emergent RNA-RNA interactions can promote stability in a nascent phototrophic endosymbiosis

“…How do such relationships avoid over-exploitation by one partner that would ultimately lead the interaction to collapse? Partner switching is one option, however the result is typically a reduced pattern of co-evolution between symbiont and host that can inhibit the process of metabolic and genetic integration, stalling the evolution of stable interactions which are needed to produce new organelles [10][11][12][13][14] . Previous studies have suggested that when selfish behaviours arise, the evolution of enforcement to punish or suppress the exploitative partner can act to restore cooperation 15,16 .…”

“…Identification of undirected 'RNAi collisions' in the P. bursaria -Chlorella system represents one such intermediary state, emergent in nature and untargeted, upon which sustained cellular interaction coupled with the potential for host-symbiont conflict could drive the selection of targeted RNA-RNA interactions. The reduced pattern of co-evolution between endosymbiont and host in the P. bursaria -Chlorella system, resulting from the potential for repeated partner switching by the host 11,34 , offers a possible explanation for why this mechanism has remained emergent.…”

Algal Diversity in Paramecium bursaria: Species Identification, Detection of Choricystis parasitica, and Assessment of the Interaction Specificity

“…After two days of incubation at 20 • C, the bacterized CM was ready for use. 3 : Friedrichsee, Saxony-Anhalt, Germany; 4 : Pond 'Pferdetränke', Oldenburg, Germany; 5 : Nymphensee, Rangsdorf, Germany; 6 : Loch Katrine, Scotland, United Kingdom; 7 : Saint Petersburg, pond in the park, Russia; 8 : Forest pond, Vyborg, Saint Petersburg region, Russia; 9 : Pond, Ardmoore, Oklahoma, USA; * Zagata et al, 2016 [60]; part. : partial.…”