Abiotic stress modifies the synthesis of alpha‐tocopherol and beta‐carotene in phytoplankton species

Abstract

We performed laboratory experiments to investi-gate whether the synthesis of the antioxidants α-tocopherol (vitamin E) and β-carotene in phytoplankton depends on changes in abiotic factors. Cultures of Nodularia spumigena, Phaeodactylum tricornutum, Skeletonema costatum, Dunaliella tertiolecta, Prorocentrum cordatum, and Rhodomonas salina were incubated at different tempe-ratures, photon flux densities and salinities for 48 h. We found that abiotic stress, within natural ecological ranges, affects the synthesis of the two antioxidants in different ways in different species. In most cases antioxidant production was stimulated by increased abiotic stress. In P. tricornutum KAC 37 and D. tertiolecta SCCAP K-0591, both good producers of this compound, α-tocopherol accumulation was negatively affected by environmentally induced higher photosystem II efficiency (Fv /Fm ). On the other hand, β-carotene accumulation was positively affected by higher Fv /Fm in N. spumigena KAC 7, P. tricornutum KAC 37, D. tertiolecta SCCAP K-0591 and R. salina SCCAP K-0294. These different patterns in the synthesis of the two compounds may be explained by their different locations and functions in the cell. While α-tocopherol is heavily involved in the protection of prevention of lipid peroxidation in membranes, β-carotene performs immediate photo-oxidative protection in the antennae complex of photosystem II. Overall, our results suggest a high variability in the antioxidant pool of natural aquatic ecosystems, which can be subject to short-term temperature, photon flux density and salinity fluctuations. The antioxidant levels in natural phytoplankton communities depend on species composition, the physiological condition of the species, and their respective strategies to deal with reactive oxygen species. Since α-tocopherol and β-carotene, as well as many other nonenzymatic antioxidants, are exclusively produced by photo-synthetic organisms, and are required by higher trophic levels through dietary intake, regime shifts in the phytoplankton as a result of large-scale environmental changes, such as climate change, may have serious consequences for aquatic food webs.

Growth, toxin production, active oxygen species and catalase activity of Microcystis aeruginosa (Cyanophyceae) exposed to temperature stress

“…However, it was already demonstrated that H 2 DCF is oxidized by other ROS, including superoxide anion radical, hydroxyl radical, peroxyl, alkoxyl, hydroperoxyl and peroxynitrite which are products of normal metabolism (Halliwell and Gutteridge, 2007). Intracellular production of ROS does not necessarily imply cellular toxicity, but oxidative stress will occur when ROS formation exceeds antioxidant defense capability or disrupts redox signaling, affecting cell functionality (Häubner et al, 2014). DCF can be oxidized by various ROS including H 2 O 2 , organic hydroperoxides, nitric oxide and peroxynitrite (Gomes et al, 2005).…”

Photoprotective and antioxidant responses to light spectrum and intensity variations in the coastal diatom Skeletonema marinoi

“…Their concentration gives important information on the cell status controlling, for example, PSII activity and therefore photosynthesis and the expression of genes involved in acclimation and defence strategies (Foyer and Shigeoka, 2010). While in higher plants, much information on the antioxidative network is available (Mullineaux et al, 2000;Mittler, 2002;Logan et al, 2006;Sharma et al, 2012), little is known in microalgae Snoeijs et al, 2011;H€ aubner et al, 2014) and in diatoms (Rijstenbil, 2002;Affan et al, 2009;Van de Poll et al, 2009).…”

Carotenoid production by the marine microalgae Nannochloropsis oculata in different low-cost culture media

“…The production of pigments by N. oculata may differ significantly according to growth conditions and medium composition (Lubi an et al, 2000). Some investigations have shown an increase in carotenoid content of N. oculata cultured under low light incidence (H€ aubner, Sylvander, Vuori & Snoeijs, 2014;Rebolloso-Fuentes et al, 2001;Sukenik, Zmora & Carmeli, 1993). Similarly, high temperature favors accumulation of beta-carotene, as happens with other carotenoids (e.g., zeaxanthin) in N. oculata.…”

“…Temperature plays an important role in microalgae metabolism, particularly in the accumulation/conversion of xanthophyll-cycle pigments (violaxanthin, antheraxanthin and zeaxanthin). In this context, some studies have shown that an increase in temperature induces the conversion of most part of violaxanthin to antheraxanthin and zeaxanthin in the xanthophyll cycle of Nannochloropsis (Gentile & Blanch, 2001;H€ aubner et al, 2014;Lubi an et al, 2000). Another important factor is culture age, according to Lubi an et al (2000) carotenoids concentration increase as the culture gets older, especially after reaching the stationary phase.…”