Differential ROS Generation in Response to Stress inSymbiodiniumspp.

Abstract

Oxidative stress inside cells occurs when the production of reactive oxygen species (ROS) is no longer efficiently counterbalanced by the generation of antioxidants. In this study, we measured the intracellular production of ROS, including hydrogen peroxide (HO), superoxide (O), and singlet oxygen (O), in cultured dinoflagellates of the genus Symbiodinium under thermal and oxidative stress. ROS tagged with fluorescent probes were measured by flow cytometry. Dissimilar Symbiodinium internal transcribed spacer 2 (ITS2) clades or phylotypes (A1, B2, E, F1) produced ROS in different quantities in response to stress. For example, when comparing the control (26 °C) to the high-temperature treatment (35 °C), Symbiodinium E showed no change in the intracellular concentrations of any of the ROS; but phylotype A1 displayed a 10-fold increase in the overall ROS concentration and a 4-fold increase in O. Under oxidative stress, when 8 mmol l HO was added to the cells, these same two Symbiodinium phylotypes increased their overall concentrations of ROS, but only Symbiodinium E showed an increase in the concentrations of O (2×) and O (3×). Therefore, not only were the stress responses of the various Symbiodinium phylotypes different but also the responses of individual phylotypes to thermal and oxidative stress were different in terms of ROS production. Variation in the quality and quantity of ROS generation and its implications for subsequent antioxidant production suggest that different stress mechanisms are at play. While our experiments were done under laboratory conditions that did not necessarily mirror ecological ones, these results provide new insight into processes inside Symbiodinium cells during stress events and add new explanations for a phylotype's susceptibility to stress.

Stony Coral Tissue Loss Disease in Florida Is Associated With Disruption of Host–Zooxanthellae Physiology

“…Zooxanthellae also produce various metabolites that can disrupt symbiosis. In response to environmental stress or exposure to pathogens, increased production by zooxanthellae of, for example, reactive oxygen species (ROS), nitric oxide, antioxidants such as dimethyl-sulfoniopropionate, and volatile organic compounds could play a role in the death of zooxanthellae and host coral cells (Mydlarz and Jacobs, 2004;Bouchard and Yamasaki, 2008;Mydlarz et al, 2009;Hawkins and Davy, 2012;McGinty et al, 2012;McLenon and DiTullio, 2012;Caruana and Malin, 2014;Wietheger et al, 2018;Lawson et al, 2019;Zhou et al, 2019). As part of their innate immune response against pathogens, corals also produce antioxidants such as melanin, with synthesis activated by cleavage of prophenoloxidase to phenoloxidase (PO) (Palmer et al, 2008).…”

Thermal and Herbicide Tolerances of Chromerid Algae and Their Ability to Form a Symbiosis With Corals

“…Although the mechanisms underlying the differences in diuron tolerances between algae are unknown, we suggest several possibilities. Firstly, high concentrations of diuron may result in chronic photoinhibition (Jones, 2005) and algae differ in their abilities to combat photodamage through the rate of repair of their PSII reaction centers (Takahashi et al, 2004, 2009), as well as exhibiting differing abilities to combat the excessive production of reactive oxygen species that likely occur from a disruption in electron flow (Lesser, 1997; Suggett et al, 2008; McGinty et al, 2012; Wietheger et al, 2018). Secondly, the low photosynthetic efficiencies exhibited by V. brassicaformis and the unknown chromerid could result in a lower base level of reactive oxygen species production that could allow higher diuron (and temperature) tolerances here.…”

Anemonia sulcata and Its Symbiont Symbiodinium as a Source of Anti-Tumor and Anti-Oxidant Compounds for Colon Cancer Therapy: A Preliminary In Vitro Study

“…This situation is known as "coral bleaching". For example, a decrease in Symbiodinium photosynthesis (30-50%) together with a reduction in superoxide dismutase activity and antioxidant activity of peridinin, diatoxanthin and the ubiquitin-proteasome pathway have been observed after bleaching [57,58]. In our case, it is possible that the light stress situation that was induced to inactivate the symbiont of Anemonia sulcata was able to trigger a greater production of ROS and, consequently, of antioxidant molecules.…”