Photoprotection mechanisms against ultraviolet radiation in Heterocapsa sp. (Dinophyceae) are influenced by nitrogen availability: Mycosporine‐like amino acids vs. xanthophyll cycle

Abstract

The photoprotective and acclimation capacity against ultraviolet radiation (UVR) was assessed for the dinoflagellate Heterocapsa sp. We examined the effect of UVR and N availability on photosynthetic activity and on the accumulation of photoprotective substances such as mycosporine-like amino acids (MAAs) and xanthophyll cycle pigments. Cells were cultivated under two different light treatments, photosynthetically active radiation (PAR) and PAR + UVR, and at two NaNO 3 concentrations, mid nitrogen (MN, 0.1 mmol L 21 ) and high nitrogen (HN, 1 mmol L 21 ) for 6 d. MAA and photosynthetic pigment contents as well as maximum quantum yield of fluorescence (F v : F m ) and electron transport rate were analyzed at the initial time and after 3 and 6 d of experimentation. F v : F m decreased because of UVR and N limitation. N enrichment reduced the deleterious effect of UVR on photosynthesis. The content of photosynthetic pigments and MAAs was higher at HN than at MN supply and a positive effect of UVR on MAA and pigment accumulation was observed, suggesting that under HN conditions the deleterious UVR effect is counteracted by MAAs. Under N limitation thermal energy dissipation takes place by the xanthophyll cycle, i.e., an increase of the de-epoxidation degree was observed under these culture conditions. However, UVR seems to favor diadinoxanthin accumulation; thus, no photoprotection through the xanthophyll cycle seems available in cells exposed to PAR + UVR and MN. We conclude that not only MAA accumulation but also N availability is very important to determine the photoprotective capacity against UVR of Heterocapsa sp.

Seasonal Variation of Mycosporine-Like Amino Acids in Three Subantarctic Red Seaweeds

“…This is consistent with the report that palythine (and shinorine) are usually the dominant MAAs in red seaweed species inhabiting more shaded places (e.g., subtidal) [16]. The high MAA content in Pyropia plicata during winter was related to nitrogen availability in seawater [18] on account of the positive correlation between N content and MAAs observed in several species [9,25,40,45,52]. However, seawater of the Magellan Strait can be considered mesotrophic waters since NO 3 concentration is rather uniform at about 0.005 mM, and no annual significant variation has ever been reported [53].…”

“…This study reveals that the contents and composition of UV-absorbing MAAs experience strong seasonal changes in the three intertidal species. These changes are probably controlled by various abiotic factors, principally by the solar radiation regime and nitrate regime as shown in both laboratory [39][40][41][42] and field [43,44].…”

Physiological and biochemical responses of <i>Emiliania huxleyi</i> to ocean acidification and warming are modulated by UV radiation

“…Similarly to our study, Xu and Gao (2015) also observed that moderate levels of UVR increased PIC production rates. It has been demonstrated that E. huxleyi can use only bicarbonate to support its calcification (Kottmeier et al, 2016;Paasche, 2002). Thus, the observed stimulation of calcification by UVA can perhaps be attributed to UVA-enhanced bicarbonate utilization (Xu and Gao, 2010).…”

Mycosporine-Like Amino Acids: Making the Foundation for Organic Personalised Sunscreens

“…In response to the generation of ROS, organisms start accumulating antioxidants to capture free radicals. In addition, as a part of the UVR interception response, organisms accumulate photoprotective compounds with UVR absorption capabilities such as mycosporine-like amino acids (MAAs) [2,3,4,5]. MAAs are found in a large number of aquatic species, including marine and freshwater organisms that have been exposed to high levels of damaging UVR [6].…”