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Microbiome. 2018 May 9;6(1):83. doi: 10.1186/s40168-018-0465-9.

Setting the pace: host rhythmic behaviour and gene expression patterns in the facultatively symbiotic cnidarian Aiptasia are determined largely by Symbiodinium.

Author information

1
The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, 52900, Ramat-Gan, Israel.
2
National Institute of Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
3
National Museum of Marine Biology and Aquarium, Checheng, Pingtung, Taiwan, Republic of China.
4
ARC Centre of Excellence for Coral Reef Studies and Department of Molecular and Cell Biology, James Cook University, Townsville, 4811, Australia. david.miller@jcu.edu.au.
5
The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, 52900, Ramat-Gan, Israel. oren.levy@biu.ac.il.

Abstract

BACKGROUND:

All organisms employ biological clocks to anticipate physical changes in the environment; however, the integration of biological clocks in symbiotic systems has received limited attention. In corals, the interpretation of rhythmic behaviours is complicated by the daily oscillations in tissue oxygen tension resulting from the photosynthetic and respiratory activities of the associated algal endosymbiont Symbiodinium. In order to better understand the integration of biological clocks in cnidarian hosts of Symbiodinium, daily rhythms of behaviour and gene expression were studied in symbiotic and aposymbiotic morphs of the sea-anemone Aiptasia diaphana.

RESULTS:

The results showed that whereas circatidal (approx. 12-h) cycles of activity and gene expression predominated in aposymbiotic morphs, circadian (approx. 24-h) patterns were the more common in symbiotic morphs, where the expression of a significant number of genes shifted from a 12- to 24-h rhythm. The behavioural experiments on symbiotic A. diaphana displayed diel (24-h) rhythmicity in body and tentacle contraction under the light/dark cycles, whereas aposymbiotic morphs showed approximately 12-h (circatidal) rhythmicity. Reinfection experiments represent an important step in understanding the hierarchy of endogenous clocks in symbiotic associations, where the aposymbiotic Aiptasia morphs returned to a 24-h behavioural rhythm after repopulation with algae.

CONCLUSION:

Whilst some modification of host metabolism is to be expected, the extent to which the presence of the algae modified host endogenous behavioural and transcriptional rhythms implies that it is the symbionts that influence the pace. Our results clearly demonstrate the importance of the endosymbiotic algae in determining the timing and the duration of the extension and contraction of the body and tentacles and temporal gene expression.

KEYWORDS:

Behaviour; Biological clocks; Circadian; Circatidal; Gene expression; Holobiont; Sea anemone Aiptasia diaphana; Symbiotic and aposymbiotic

PMID:
29739445
PMCID:
PMC5941691
DOI:
10.1186/s40168-018-0465-9
[Indexed for MEDLINE]
Free PMC Article

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