Oxidative stress and apoptotic events during thermal stress in the symbiotic sea anemone, Anemonia viridis

Abstract

Symbiosis between cnidarian and photosynthetic protists is widely distributed over temperate and tropical seas. These symbioses can periodically breakdown, a phenomenon known as cnidarian bleaching. This event can be irreversible for some associations subjected to acute and/or prolonged environmental disturbances, and leads to the death of the animal host. During bleaching, oxidative stress has been described previously as acting at molecular level and apoptosis is suggested to be one of the mechanisms involved. We focused our study on the role of apoptosis in bleaching via oxidative stress in the association between the sea anemone Anemonia viridis and the dinoflagellates Symbiodinium species. Characterization of caspase‐like enzymes were conducted at the biochemical and molecular level to confirm the presence of a caspase‐dependent apoptotic phenomenon in the cnidarian host. We provide evidence of oxidative stress followed by induction of caspase‐like activity in animal host cells after an elevated temperature stress, suggesting the concomitant action of these components in bleaching.

The Effects of UV Exposure on the Antioxidant Enzyme Systems of Anemones

“…RICHIER et al studied the effects of temperature and increased UV radiation in the symbiotic cnidarian Anthopleura elegantissima transcriptome. The results of this study corroborate that the stress response results in overproduction of the ROS in the aerobic metabolism (RICHIER et al, 2006;RICHIER et al, 2008).…”

Hyperthermic stress-induced increase in the expression of glutamate-cysteine ligase and glutathione levels in the symbiotic sea anemone Aiptasia pallida

“…2). Earlier studies have documented that heat-stress evokes oxidative and nitrosative stress in symbiotic anemones (Dunn et al, 2002;Perez and Weis 2006;Richier et al, 2006); thus, the increase in GCLC gene expression is likely to reflect the increased demand of intracellular GSH as an adaptive response. The increase in total GSH amounts could be due to a number of reasons, all of which may play important roles during the process of cnidarian bleaching.…”

“…The redox environment of the cell could therefore selectively regulate oxidative stress signaling by balancing MEKK1 versus ASK1 activities to inhibit or promote the induction of apoptosis. Apoptosis has been suggested as an underlying mechanism of cnidarian bleaching (Richier et al, 2006;Dunn et al, 2007b) and therefore, studying the role of glutathione in the context of hyperthermal stressinduced apoptotic signaling pathways would represent an exciting field of future research. Finally, S-glutathionylation of constitutively expressed heat-shock protein 70 has been shown to induce an increase in its chaperone activity (Hoppe et al, 2004), which could be a conserved post-translational heat-shock response in A. pallida.…”

Differential coral bleaching—Contrasting the activity and response of enzymatic antioxidants in symbiotic partners under thermal stress

“…On the other hand, they also show that host catalase activity, if viewed as an isolated proxy, may not be protective or predictive of bleaching, even though a connection between ROS scavenging and activation of apoptotic-like pathways was evident in the thermally susceptible coral. This interspecific variability in ROS production-apoptosis regulation (Richier et al, 2006;Tchernov et al, 2011) is worthy of further attention.…”