Symbiosis modulates gene expression of symbionts, but not coral hosts, under thermal challenge

Aichelman, Hannah E.; Huzar, Alexa K.; Wuitchik, Daniel M.; Atherton, Kathryn F.; Wright, Rachel M.; Dixon, Groves; Schlatter, E.; Haftel, Nicole; Davies, Sarah W.

doi:10.1111/mec.17318

Cited by 2 publications

(2 citation statements)

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“…Symbiont gene expression responses in both datasets were minimal compared to those of their hosts, with an order of magnitude fewer differentially expressed genes (DEGs) in the LME samples and zero DEGs in the ex situ deoxygenation samples (Figures 1c and 2c ). Muted algal responses to stress are common in gene expression experiments (Aichelman et al., 2024 ; Barshis et al., 2014 ; Baumgarten et al., 2013 ; Davies et al., 2018 ; Leggat et al., 2011 ) and may suggest that the alga's residence inside the host buffers them from external stress. Despite a muted molecular response of Symbiodinaceae compared to the host (Figure 1 ), we still found significant differentially expressed genes in B. minutum when compared between host species, site, and affected‐lesion samples (AL vs. AH and AL vs. U comparisons) (Table S5 ).…”

Section: Discussionmentioning

confidence: 99%

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Intersection of coral molecular responses to a localized mortality event and ex situ deoxygenation

Strader,

Wright,

Pezner

et al. 2024

Ecology and Evolution

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In July 2016, East Bank of Flower Garden Banks (FGB) National Marine Sanctuary experienced a localized mortality event (LME) of multiple invertebrate species that ultimately led to reductions in coral cover. Abiotic data taken directly after the event suggested that acute deoxygenation contributed to the mortality. Despite the large impact of this event on the coral community, there was no direct evidence that this LME was driven by acute deoxygenation, and thus we explored whether gene expression responses of corals to the LME would indicate what abiotic factors may have contributed to the LME. Gene expression of affected and unaffected corals sampled during the mortality event revealed evidence of the physiological consequences of the LME on coral hosts and their algal symbionts from two congeneric species (Orbicella franksi and Orbicella faveolata). Affected colonies of both species differentially regulated genes involved in mitochondrial regulation and oxidative stress. To further test the hypothesis that deoxygenation led to the LME, we measured coral host and algal symbiont gene expression in response to ex situ experimental deoxygenation (control = 6.9 ± 0.08 mg L−1, anoxic = 0.083 ± 0.017 mg L−1) in healthy O. faveolata colonies from the FGB. However, this deoxygenation experiment revealed divergent gene expression patterns compared to the corals sampled during the LME and was more similar to a generalized coral environmental stress response. It is therefore likely that while the LME was connected to low oxygen, it was a series of interconnected stressors that elicited the unique gene expression responses observed here. These in situ and ex situ data highlight how field responses to stressors are unique from those in controlled laboratory conditions, and that the complexities of deoxygenation events in the field likely arise from interactions between multiple environmental factors simultaneously.

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Section: Discussionmentioning

confidence: 99%

“…How to cite this article: Strader, M. E., Wright, R. M., Pezner, A. K., Nuttall, M. F., Aichelman, H. E., & Davies, S. W. (2024).…”

Section: Data Ava I L a B I L I T Y S Tat E M E N Tmentioning

confidence: 99%

Intersection of coral molecular responses to a localized mortality event and ex situ deoxygenation

Strader,

Wright,

Pezner

et al. 2024

Ecology and Evolution

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Photosymbiosis reduces the environmental stress response under a heat challenge in a facultatively symbiotic coral

Wuitchik,

Aichelman,

Atherton

et al. 2024

Sci Rep

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The symbiosis between corals and dinoflagellates of the family Symbiodiniaceae is sensitive to environmental stress. The oxidative bleaching hypothesis posits that extreme temperatures lead to accumulation of photobiont-derived reactive oxygen species ROS, which exacerbates the coral environmental stress response (ESR). To understand how photosymbiosis modulates coral ESRs, these responses must be explored in hosts in and out of symbiosis. We leveraged the facultatively symbiotic coral Astrangia poculata, which offers an opportunity to uncouple the ESR across its two symbiotic phenotypes (brown, white). Colonies of both symbiotic phenotypes were exposed to three temperature treatments for 15 days: (i) control (static 18 °C), (ii) heat challenge (increasing from 18 to 30 °C), and (iii) cold challenge (decreasing from 18 to 4 °C) after which host gene expression was profiled. Cold challenged corals elicited widespread differential expression, however, there were no differences between symbiotic phenotypes. In contrast, brown colonies exhibited greater gene expression plasticity under heat challenge, including enrichment of cell cycle pathways involved in controlling photobiont growth. While this plasticity was greater, the genes driving this plasticity were not associated with an amplified environmental stress response (ESR) and instead showed patterns of a dampened ESR under heat challenge. This provides nuance to the oxidative bleaching hypothesis and suggests that, at least during the early onset of bleaching, photobionts reduce the host’s ESR under elevated temperatures in A. poculata.

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Symbiosis modulates gene expression of symbionts, but not coral hosts, under thermal challenge

Cited by 2 publications

References 78 publications

Intersection of coral molecular responses to a localized mortality event and ex situ deoxygenation

Intersection of coral molecular responses to a localized mortality event and ex situ deoxygenation

Photosymbiosis reduces the environmental stress response under a heat challenge in a facultatively symbiotic coral

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