Mechanisms underlying turgor regulation in the estuarine alga Vaucheria erythrospora (Xanthophyceae) exposed to hyperosmotic shock

Abstract

Aquatic organisms are often exposed to dramatic changes in salinity in the environment. Despite decades of research, many questions related to molecular and physiological mechanisms mediating sensing and adaptation to salinity stress remain unanswered. Here, responses of Vaucheria erythrospora, a turgor-regulating xanthophycean alga from an estuarine habitat, have been investigated. The role of ion uptake in turgor regulation was studied using a single cell pressure probe, microelectrode ion flux estimation (MIFE) technique and membrane potential (Em ) measurements. Turgor recovery was inhibited by Gd(3+) , tetraethylammonium chloride (TEA), verapamil and orthovanadate. A NaCl-induced shock rapidly depolarized the plasma membrane while an isotonic sorbitol treatment hyperpolarized it. Turgor recovery was critically dependent on the presence of Na(+) but not K(+) and Cl(-) in the incubation media. Na(+) uptake was strongly decreased by amiloride and changes in net Na(+) and H(+) fluxes were oppositely directed. This suggests active uptake of Na(+) in V. erythrospora mediated by an antiport Na(+) /H(+) system, functioning in the direction opposite to that of the SOS1 exchanger in higher plants. The alga also retains K(+) efficiently when exposed to high NaCl concentrations. Overall, this study provides insights into mechanisms enabling V. erythrospora to regulate turgor via ion movements during hyperosmotic stress.

RNAi screening for modulators of an osmo-sensitive gene response to extracellular matrix damage reveals negative feedback and interactions with translation inhibition

“…Exposure to high osmolarity environments causes osmotic water loss and reduced turgor pressure that could initiate a mechanical signal for stress response activation [ 22 , 63 – 65 ]. Mutation or loss of furrow collagens may mimic mechanical changes caused by hyperosmotic water loss by relaxing mechanical strain on turgor pressure sensors [ 66 – 68 ].…”

Uncovering the complex cell wall of Neochloris oleoabundans, a promising green microalga

“…Previous studies on marine algae established that some microalgae are enriched in sulphated polysaccharides including β-(1→4)-D-mannans, (1→3)-β -Larabinopyranans and other sulphated polysaccharides containing galactose, glucose and arabinose (Aquino et al, 2011;Fernández et al, 2012;Fernández et al, 2013;Synytsya et al, 2015). Marine algae are able to resist the saline environment on account of particular mechanisms such as sodium exclusion or accumulation of sulphated polysaccharides (Aquino et al, 2011;Gimmler, 2000;Muralidhar et al, 2015;Synytsya et al, 2015). The latter mechanism, which is unique to marine algae, is considered to be a strategy of adaptation in marine territories and is also existent in (some) halophyte terrestrial plants (Aquino et al, 2011;Synytsya et al, 2015).…”