Different Endosymbiotic Interactions in Two Hydra Species Reflect the Evolutionary History of Endosymbiosis

Masakazu Ishikawa, Ikuko Yuyama, Hiroshi Shimizu, Masafumi Nozawa, Kazuho Ikeo, Takashi Gojobori

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21 Scopus citations


Endosymbiosis is an important evolutionary event for organisms, and there is widespread interest in understanding the evolution of endosymbiosis establishment. Hydra is one of the most suitable organisms for studying the evolution of endosymbiosis. Within the genus Hydra, H. viridissima and H. vulgaris show endosymbiosis with green algae. Previous studies suggested that the endosymbiosis in H. vulgaris took place much more recently than that in H. viridissima, noting that the establishment of the interaction between H. vulgaris and its algae is not as stable as in H. viridissima. To investigate the on-going process of endosymbiosis, we first compared growth and tolerance to starvation in symbiotic and aposymbiotic polyps of both species. The results revealed that symbiotic H. viridissima had a higher growth rate and greater tolerance to starvation than aposymbiotic polyps. By contrast, growth of symbiotic H. vulgaris was identical to that of aposymbiotic polyps, and symbiotic H. vulgaris was less tolerant to starvation. Moreover, our gene expression analysis showed a pattern of differential gene expression in H. viridissima similar to that in other endosymbiotically established organisms, and contrary to that observed in H. vulgaris. We also showed that H. viridissima could cope with oxidative stress that caused damage, such as cell death, in H. vulgaris. These observations support the idea that oxidative stress related genes play an important role in the on-going process of endosymbiosis evolution. The different evolutionary stages of endosymbiosis studied here provide a deeper insight into the evolutionary processes occurring toward a stable endosymbiosis.
Original languageEnglish (US)
Pages (from-to)2155-2163
Number of pages9
JournalGenome Biology and Evolution
Issue number7
StatePublished - Jun 19 2016

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: The authors thank Ikuko Masujima, Takako Komatsu, and Tae
Yamada for helping with Hydra spp. maintenance, and the
collaborators of the Beijing Institute for Genomics (BGI) and
the Bioscience Core Lab in King Abdullah University of Science
and Technology (KAUST) for carrying out sequencing. The authors
would also like to thank the ROIS National Institute of
Genetics for the use of their NIG supercomputer. This work was
supported by the Graduate University for Advanced Studies
(SOKENDAI) to M.I. and by KAUST baseline fund to T.G.


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