During embryonic development, cells of the green alga Oophila amblystomatis enter cells of the salamander Ambystoma maculatum forming an endosymbiosis. Here, using de novo dual-RNA seq, we compared the host salamander cells that harbored intracellular algae to those without algae and the algae inside the animal cells to those in the egg capsule. This two-by-two-way analysis revealed that intracellular algae exhibit hallmarks of cellular stress and undergo a striking metabolic shift from oxidative metabolism to fermentation. Culturing experiments with the alga showed that host glutamine may be utilized by the algal endosymbiont as a primary nitrogen source. Transcriptional changes in salamander cells suggest an innate immune response to the alga, with potential attenuation of NF-κB, and metabolic alterations indicative of modulation of insulin sensitivity. In stark contrast to its algal endosymbiont, the salamander cells did not exhibit major stress responses, suggesting that the host cell experience is neutral or beneficial.
Bibliographical noteFunding Information:
We thank S Obado, M Bradic, S Thurston for technical comments and critical reviews and R Voss for providing the unpublished V4 assembly of an axolotl (Ambystoma mexicanum) transcriptome. EHill and H Zhang were partially supported by an HHMI award to Gettysburg College. The work was supported by an NSF EAGER to R. Kerney, E Kim, and JA Burns (#1428065) and NSF CAREER to E Kim (#1453639). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
© Burns et al.