Photoprotective Compounds Research Articles

Photosynthetic performance and photoprotection of Cystoseira humilis (Phaeophyceae) and Digenea simplex (Rhodophyceae) in an intertidal rock pool

Rock pools are dynamic and intermittently isolated habitats in the rocky intertidal. In this study, we assessed if the photosynthesis and physiological activity of the brown macroalga Cystoseira humilis and the red macroalga Digenea simplex in a rock pool at Lanzarote Island (eastern Atlantic) was affected due by their vertical distribution. Photosynthetic responses were measured at three depth levels (0.05–1m, 0.4–2.5 and 3.5m) through in vivo chlorophyll a fluorescence, in particular the maximal quantum yield (Fv/Fm) as an estimator of the physiological status and photoinhibition, and the electron transport rate (ETR) as an estimator of the photosynthetic capacity. Algal photoprotection and photodamage processes were related to algal zonation; shallow-water thalli had active mechanisms of dynamic photoinhibition compared to algae from the deeper level. The progressive increase of solar radiation during the day caused different responses for each macroalga, where C. humilis showed lower photoinhibition, higher ETR values than D. simplex. Algae from the shallow level had lower pigment content and higher resistance to high solar radiation through the accumulation of photoprotective compounds and higher antioxidant activity (DPPH) compared to thalli from the deeper level. In summary, this study corroborates that algae are vertically distributed inside rock pools according to their adaptive responses to light-induced stress conditions and that photoacclimation occur in a short-term period.

Occurrence and induction of a ultraviolet‐absorbing substance in the cyanobacterium Fischerella muscicola TISTR8215

SummaryThe filamentous cyanobacterium Fischerella muscicola TISTR8215 was tested for the presence of ultraviolet (UV)‐absorbing mycosporine‐like amino acids (MAAs) and their induction by UV radiation. Reverse‐phase high performance liquid chromatographic coupled with photodiode‐array detection studies revealed the presence of a MAA having an absorption maximum at 332 nm and a retention time of around 16.1 min. Based on absorption maximum, the compound was designated as M‐332. This is the first report for the occurrence of a MAA and its inducibility as influenced by UV radiation in Fischerella strains studied so far. Photosynthetically active radiation (PAR) had no significant impact on MAA induction. PAR + UV‐A radiation significantly induced the synthesis of M‐332; however, PAR + UV‐A + UV‐B radiation conferred highest impact on MAA synthesis. The cultures exposed to alternate light and dark conditions showed the induction of M‐332 synthesis mostly during the light period in contrast to the decreased levels of M‐322 during the dark period suggesting a circadian induction of its synthesis. Overall results indicate that F. muscicola may protect itself from deleterious short wavelength UV radiation by synthesizing the photoprotective compounds particularly during summer time in its natural brightly‐lit habitats.

Chemical characterization and photoprotective activity measurement of extracts from the red macroalga Solieria chordalis

Abstract The photoadaptive responses of macroalgal communities to abiotic stresses have been studied, and a number of UV-absorbing molecules have been identified. Among these compounds, photoprotective compounds such as mycosporine-like amino acids and carotenoids have been isolated from various red macroalgal species. However, several substances still need to be characterized. We describe the preparation of photoprotective extracts obtained from Solieria chordalis. Two solvents, 2-octyl dodecanol and octyldodecyl ester of l-pyrrolidone carboxylic acid, were selected based on their cosmetic functions for performing an ultrasound-assisted extraction. The efficiency of extraction was monitored by spectrophotometry and in vitro photoprotective activity measurements. 2-Octyl dodecanol and octyldodecyl ester of l-pyrrolidone carboxylic acid extracts showed maximum absorption wavelengths ranging from 280 to 340 nm and 270 to 350 nm, respectively. The anti UV-B capacity for protecting a synthetic chlorophyll solution was assessed by measuring its pseudo first-order degradation kinetics at room temperature. Under irradiation at 312 nm, chlorophyll introduced in the 2-octyl dodecanol S. chordalis extract showed the slowest degradation kinetics with a half-life t1/2 of 121.0 min. Several compounds were detected in the seaweed extract by high-performance liquid chromatography. Among them, the mycosporine-like amino acid, palythenic acid, was detected in the algal extract.

Protective effect of trehalose-loaded liposomes against UVB-induced photodamage in human keratinocytes.

Trehalose, a naturally occurring non-reducing disaccharide, is known to act as a major protein stabilizer that can reduce ultraviolet B (UVB)-induced corneal damage when topically applied to the eye. However, due to the low skin permeability of trehalose, which makes the development of topical formulations difficult, its use as a skin photoprotective agent has been limited. Previous findings demonstrated that liposomes may significantly improve the intracellular delivery of trehalose. Therefore, the present study aimed to assess the protective effects of trehalose-loaded liposomes against UVB-induced photodamage using the immortalized human keratinocyte cell line, HaCaT. The effects were also compared to those of the common skin photoprotective compounds, including L-carnosine, L-(+)-ergothioneine, L-ascorbic acid and DL-α-tocopherol. The levels of cyclobutane pyrimidine dimers, 8-hydroxy-2'-deoxyguanosine and protein carbonylation in HaCaT cells were used as biological markers of UVB-induced damage. Compared to other compounds, trehalose-loaded liposomes showed the highest efficacy in reducing the levels of the three markers following UVB irradiation of HaCaT cells (all P<0.001 when compared to each of the four other photoprotective compounds). Therefore, these findings indicate that there may be a clinical application for trehalose-loaded liposomes, and further studies should be performed to assess the potential usefulness in skin photoprotection and the prevention of non-melanoma skin cancer.

An Uncharacterized Apocarotenoid-Derived Signal Generated in ζ-Carotene Desaturase Mutants Regulates Leaf Development and the Expression of Chloroplast and Nuclear Genes in Arabidopsis.

In addition to acting as photoprotective compounds, carotenoids also serve as precursors in the biosynthesis of several phytohormones and proposed regulatory signals. Here, we report a signaling process derived from carotenoids that regulates early chloroplast and leaf development. Biosynthesis of the signal depends on ζ-carotene desaturase activity encoded by the ζ-CAROTENE DESATURASE (ZDS)/CHLOROPLAST BIOGENESIS5 (CLB5) gene in Arabidopsis thaliana. Unlike other carotenoid-deficient plants, zds/clb5 mutant alleles display profound alterations in leaf morphology and cellular differentiation as well as altered expression of many plastid- and nucleus-encoded genes. The leaf developmental phenotypes and gene expression alterations of zds/clb5/spc1/pde181 plants are rescued by inhibitors or mutations of phytoene desaturase, demonstrating that phytofluene and/or ζ-carotene are substrates for an unidentified signaling molecule. Our work further demonstrates that this signal is an apocarotenoid whose synthesis requires the activity of the carotenoid cleavage dioxygenase CCD4.

Marine CDOM accumulation during a coastal Arctic mesocosm experiment: No response to elevated pCO2 levels

AbstractA large‐scale multidisciplinary mesocosm experiment in an Arctic fjord (Kongsfjorden, Svalbard; 78°56.2′N) was used to study Arctic marine food webs and biogeochemical elements cycling at natural and elevated future carbon dioxide (CO2) levels. At the start of the experiment, marine‐derived chromophoric dissolved organic matter (CDOM) dominated the CDOM pool. Thus, this experiment constituted a convenient case to study production of autochthonous CDOM, which is typically masked by high levels of CDOM of terrestrial origin in the Arctic Ocean proper. CDOM accumulated during the experiment in line with an increase in bacterial abundance; however, no response was observed to increased pCO2 levels. Changes in CDOM absorption spectral slopes indicate that bacteria were most likely responsible for the observed CDOM dynamics. Distinct absorption peaks (at ~ 330 and ~ 360 nm) were likely associated with mycosporine‐like amino acids (MAAs). Due to the experimental setup, MAAs were produced in absence of ultraviolet exposure providing evidence for MAAs to be considered as multipurpose metabolites rather than simple photoprotective compounds. We showed that a small increase in CDOM during the experiment made it a major contributor to total absorption in a range of photosynthetically active radiation (PAR, 400–700 nm) and, therefore, is important for spectral light availability and may be important for photosynthesis and phytoplankton groups composition in a rapidly changing Arctic marine ecosystem.

Photoprotective function of mycosporine-like amino acids in a bipolar diatom (Porosira glacialis): evidence from ultraviolet radiation and stable isotope probing

This study investigated the synthesis of photoprotective compounds by Bacillariophyceae (Porosira glacialis) in real time using a 13C tracer. Our results show a relationship between the net production rates of mycosporine-like amino acids (MAAs) and photoprotective pigments such as diadinoxanthin (DD). After 24 h, the total carbon uptake rate of P. glacialis was higher when exposed to photosynthetically active radiation (PAR) than when exposed to ultraviolet radiation (UVR). However, with time, the total carbon uptake rate and turnover rate of P. glacialis exposed to UVR increased to the point where the net production rate of MAAs under UVR was higher than that of P. glacialis exposed to PAR. The differences in MAA and DD production rates and carbon uptake indicate the production of MAA and DD as a defense strategy in response to UV-induced damage. The results of this study provide insight into the synthetic pathways of photoprotective compounds and the carbon cycle within P. glacialis cells and reveal contrasting patterns in the production of MAAs and xanthophyll compounds such as DD over time.

Direct and indirect acquisition of photoprotective compounds in crab larvae of coastal Patagonia (Argentina)

Fil: Hernandez Moresino, Rodrigo Daniel. Fundacion Playa Union. Estacion de Fotobiologia Playa Union; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina

Effects of a submarine eruption on the performance of two brown seaweeds

World oceans are becoming more acidic as a consequence of CO2 anthropogenic emissions, with multiple physiological and ecological implications. So far, our understanding is mainly limited to some species through in vitro experimentation. In this study, we took advantage of a recent submarine eruption (from October 2011 to March 2012) at ~1 nautical mile offshore El Hierro Island (Canary Islands, central east Atlantic) to determine whether altered physical–chemical conditions, mainly sudden natural ocean acidification, affected the morphology, photosynthesis (in situ Chl-a fluorescence) and physiological performance (photo-protective mechanisms and oxidative stress) of the conspicuous brown seaweeds Padina pavonica—a species with carbonate deposition – and Lobophora variegata—a species without carbonate on thallus surfaces – , both with similar morphology. Seaweeds were sampled twice: November 2011 (eruptive phase with a pH drop of ca. 1.22 units relative to standard conditions) and March 2012 (post-eruptive phase with a pH of ca. 8.23), on two intertidal locations adjacent to the eruption and at a control location. P. pavonica showed decalcification and loss of photo-protective compounds and antioxidant activity at locations affected by the eruption, behaving as a sun-adapted species during lowered pH conditions. At the same time, L. variegata suffered a decrease in photo-protective compounds and antioxidant activity during the volcanic event, but its photosynthetic performance remained unaltered. These results reinforce the idea that calcareous seaweeds, as a whole, are more sensitive than non-calcareous seaweeds to alter their performance under scenarios of reduced pH.

Spectral absorbance of benthic cladoceran carapaces as a new method for inferring past UV exposure of aquatic biota

We developed a method for measuring fossil cladoceran (Branchiopoda) carapace absorbance to infer past ultraviolet radiation (UV) exposure in lakes. This was done under the presumptions that cladocerans synthesize photoprotective compounds, of which melanin is the main UV-absorbing pigment, to their exoskeletons and melanin is preserved in sedimentary cladoceran remains. We extracted large-sized cladoceran (benthic Alona spp.) carapaces from subsections of sediment cores from two environmentally divergent lakes; a humic boreal forest lake in eastern Finland (past 1500 years) and a clear-water mountain lake in the Austrian Alps (past 300 years). We measured the absorbance of extracted carapaces with a spectrophotometer under visible light and UV wavelengths using an adapter, which was designed to hold the microfossils. When compared to the spectrum of synthetic melanin, the shapes of absorbance spectra at the 700−280 nm range suggested that the fossil carapaces contained melanin. The carapace absorbance under UV throughout the sediment cores was significantly higher in the clear-water alpine lake than in the humic boreal lake reflecting differences in the general underwater UV and optical environments between the sites. In addition, carapace absorbance was significantly higher during the Little Ice Age (LIA) than during pre- or post-LIA periods in both lakes. In the alpine lake, this was most likely a response to increased underwater UV induced by reduced primary production and more transparent water column during the cold summers of LIA, whereas reduced input of carbon compounds from the catchment through elongated permafrost and ice-cover periods likely induced higher water transparency in the boreal lake during this cold climate phase. We conclude that fossil melanin provides a good estimation of past underwater UV exposure in lakes with large cladoceran carapaces preserved in sediments and that the method introduced here is easy and cost- and time-efficient technique to be widely used in paleoaquatic UV inferences.

Photoheterotrophic growth unprecedentedly increases the biosynthesis of mycosporine-like amino acid shinorine in the cyanobacterium Anabaena sp., isolated from hot springs of Rajgir (India)

Cyanobacteria are known to biosynthesize mycosporine-like amino acids (MAAs) as photoprotective compounds against ultraviolet radiation. Anabaena sp., isolated from the hot springs of Rajgir, India, produces a single MAA shinorine (retention time = 2.2 min and absorption maximum at 334 nm) as purified by high-performance liquid chromatography. The MAA biosynthesis was under constitutive control in this cyanobacterium; however, PAR + UV-A + UV-B radiation was found to have highest impact on MAA synthesis. MAA biosynthesis is dependent on photosynthesis for the carbon source since the inhibitory effect of DCMU on MAA synthesis was overcome by externally added fructose. Our results suggest that there is no direct involvement of photosystem II dependent linear electron transport in MAA biosynthesis. However, utilization of energy derived from photosystem I dependent cyclic electron transport in MAA biosynthesis cannot be ruled out. This study also reveals that photoheterotrophic growth can support highest MAA biosynthesis under laboratory conditions in comparison with photoautotrophic and photomixotrophic growth. Thus, photoheterotrophic growth condition can be used for the large-scale production of pharmaceutically important MAAs from cyanobacteria for an industrial application.

Characterization of UV-screening compounds, mycosporine-like amino acids, and scytonemin in the cyanobacteriumLyngbyasp. CU2555

Ultraviolet-screening compounds from the cyanobacterium Lyngbya sp. CU2555 were partially characterized and investigated for their induction by UV radiation, stability under different abiotic factors, and free radical scavenging activity. Based on the high-performance liquid chromatography coupled with diode array detector and ion trap liquid chromatography/mass spectrometry analysis, the compounds were identified as palythine (UVλ max: 319 nm; m/z: 245), asterina (UVλ max: 330 nm; m/z: 289), scytonemin (UVλ max: 384 nm; mw: 544), and reduced scytonemin (UVλ max: 384 nm; m/z: 547). This is the first report for the occurrence of palythine, asterina, and an unknown mycosporine-like amino acids (MAA), M-312 (UVλ max: 312 ± 1 nm), in addition to scytonemin and reduced scytonemin in Lyngbya strains studied so far. Induction of MAAs and scytonemin was significantly more prominent upon exposure to UV-A + UV-B radiation. Both MAAs and scytonemin were highly resistant to some physicochemical factors such as UV-B, heat, and a strong oxidizing agent and exhibited strong antioxidant activity. These results indicate that the studied cyanobacterium may protect itself from deleterious short-wavelength radiation by synthesizing photoprotective compounds in response to harmful UV radiation.

Manganese toxicity and UV-B radiation differentially influence the physiology and biochemistry of highbush blueberry (Vaccinium corymbosum) cultivars.

Manganese (Mn2+) toxicity or UV-B radiation and their individual effects on plants have been documented previously. However, no study about the combined effect of these stresses is available. We evaluated the individual and combined effects of excess Mn2+ and UV-B radiation on physiological and biochemical parameters in two highbush blueberry (Vaccinium corymbosum L.) cultivars differing in resistance to Mn toxicity (Brigitta (resistant) and Bluegold (sensitive)). Plants grown in Hoagland nutrient solution were subjected to the following treatments: 2µM MnCl2 (control), 500µM MnCl2 (toxic Mn2+), UV-B radiation (a daily dose of 94.4kJm-2), and the combined treatment (toxic Mn2++UV-B) for 30 days. In both cultivars, the Mn2++UV-B treatment caused a more negative effect on net photosynthesis (Pn), stomatal conductance (gs), the photochemical parameters of PSII and the chl a/b ratio than the treatments with toxic Mn2+ or UV-B alone. However, Brigitta showed also a better acclimation response in Pn and gs than Bluegold at the end of the experiment. The Mn2++UV-B treatment inhibited growth, enhanced radical scavenging activity and superoxide dismutase activity, and increased the concentration of total UV-absorbing compounds, phenols and anthocyanins, mainly in Bluegold. In conclusion, Mn-resistant Brigitta showed a better acclimation response and greater resistance to the combined stress of Mn2+ toxicity and UV-B exposure than the Mn-sensitive Bluegold. An increased concentration of photoprotective compounds and enhanced resistance to oxidative stress in Brigitta could underpin increased resistance to the combined stress.

Mycosporine-like amino acids (MAAs): qualitative analysis of photoprotective compounds in Laurencia complex seaweed species (Ceramiales, Rhodophyta) from Espírito Santo State, Brazil

Mycosporine-like amino acids (MAAs): qualitative analysis of photoprotective compounds in Laurencia complex seaweed species (Ceramiales, Rhodophyta) from Espírito Santo State, Brazil

Screening of specific photoprotective compounds in Ulvophyceae (Chlorophyta) from the Southeastern Brazilian coastline

Screening of specific photoprotective compounds in Ulvophyceae (Chlorophyta) from the Southeastern Brazilian coastline

UV radiation-induced accumulation of photoprotective compounds in the green alga Tetraspora sp. CU2551

The effect of UV radiation on the accumulation of novel mycosporine-like amino acids (MAAs) along with their photoprotective function was investigated in the green alga Tetraspora sp. CU2551. No UV-absorbing compound was detected in this organism growing under normal light condition while two MAAs with absorption maxima at 324nm and 322nm were found to be accumulated after UV irradiation. The effects of UV exposure time with different cut-off filter foils namely 295 (PAR+UV-A+UV-B), 320 (PAR+UV-A) and 395nm (PAR only) were studied on induction of the synthesis of these MAAs. Concentration of MAAs was found to increase with increase in exposure time under UV radiation. Furthermore, the antioxidant and photoprotective action of these MAAs was also investigated. The role of MAAs in diminishing the UV-induced production of ROS invivo was also demonstrated using the oxidant-sensing probe 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) and results obtained supported the results of DPPH free radical scavenging assay. The MAAs also exhibited efficient photoprotective ability on Escherichia coli cells against UV-B stress. Thus, the MAAs in Tetraspora sp. CU2551 may act as efficient antioxidants as well as UV-sunscreen. This is the first report for the UV-induced synthesis and co-accumulation of these MAAs and their photoprotective actions in Tetraspora sp. which is a member of the class Chlorophyceae. Moreover, UV-induced accumulation as well as photoprotective function of these compounds may facilitate this chlorophyte to perform important ecological functions in harsh environmental conditions with high UV-B fluxes in their brightly lit habitats.

Probing a Coral Genome for Components of the Photoprotective Scytonemin Biosynthetic Pathway and the 2-Aminoethylphosphonate Pathway

Genome sequences of the reef-building coral, Acropora digitifera, have been decoded. Acropora inhabits an environment with intense ultraviolet exposure and hosts the photosynthetic endosymbiont, Symbiodinium. Acropora homologs of all four genes necessary for biosynthesis of the photoprotective cyanobacterial compound, shinorine, are present. Among metazoans, these genes are found only in anthozoans. To gain further evolutionary insights into biosynthesis of photoprotective compounds and associated coral proteins, we surveyed the Acropora genome for 18 clustered genes involved in cyanobacterial synthesis of the anti-UV compound, scytonemin, even though it had not previously been detected in corals. We identified candidates for only 6 of the 18 genes, including tyrP, scyA, and scyB. Therefore, it does not appear that Acropora digitifera can synthesize scytonemin independently. On the other hand, molecular phylogenetic analysis showed that one tyrosinase gene is an ortholog of vertebrate tyrosinase genes and that the coral homologs, scyA and scyB, are similar to bacterial metabolic genes, phosphonopyruvate (ppyr) decarboxylase and glutamate dehydrogenase (GDH), respectively. Further genomic searches for ppyr gene-related biosynthetic components indicate that the coral possesses a metabolic pathway similar to the bacterial 2-aminoethylphosphonate (AEP) biosynthetic pathway. The results suggest that de novo synthesis of carbon-phosphorus compounds is performed in corals.

Population‐specific responses to light influence herbivory in the understory shrub Lindera benzoin

Plants display photosynthetic plasticity in response to variation in light environment, and the extent of this plasticity often varies with genotype, i.e., genotype x environment interaction. Herbivory may also covary with light environment as a result of light-induced changes in photosynthetic traits. For example, greater levels of photoprotective phenolic compounds in high-light environments may reduce host quality to herbivores. We investigated intraspecific variation in photosynthetic responses to light and its consequences for herbivory in the understory shrub, Lindera benzoin (Lauraceae). We transplanted five plants from eight populations (N = 240) into three replicate sun and shade common gardens. Two years after transplantation, we tested for population x light environment interactions in six photosynthesis-related responses: specific leaf area, water content, chlorophyll content, chlorophyll fluorescence (F(0)), maximum quantum yield (F(v)/F(m)), and total phenolics. We assessed seasonal herbivory and consumption by a specialist lepidopteran herbivore (Epimecis hortaria). This allowed us to test for (1) population-specific patterns of photosynthetic acclimation and photoinhibition, (2) population-specific production of phenolics in response to photoinhibition, and (3) population-specific photosynthetic responses that contribute to population x light environment interactions in herbivory. Population X light environment interactions were insignificant in leaf variables but statistically significant for herbivory measured as consumption by E. hortaria. We found similar trends for population x light environment interactions in seasonal herbivory. Total phenolics and minimum chlorophyll fluorescence (F(0)) were significant covariates with herbivory, but their effects depended on light environment and population of origin. High-light environments eliminated differences among populations in how these leaf variables affected herbivory, while population-specific relationships were apparent in the shade. Analysis of total phenolics revealed that they were likely induced by photoinhibition, but that this response varied among the populations we assessed. However, phenolics increased herbivory in L. benzoin, which would limit the fitness value of this protective response to light-induced photoinhibition. Our results suggest that herbivores could affect evolution of photosynthetic plasticity in L. benzoin.

Characterization of PhotoprotectiveCompounds in Marine Zooplankton of the Southwest Coast of India: An Ecological Perspective

Inthe marine environment, organisms are under threat due to several environmental fluctuations such as ul- traviolet (UV) radiation, coastal pollution etc. However, it is encouraging to note that the marine organisms try to protect themselves from UV-radiation by synthesizing photprotective compounds. Since phytoplankton can synthesize the UV-protecective compounds and are grazed by zooplankton, we investigated the presence of photoprotective compounds in zooplankton. In this context, a study has been conducted for the first time in the shelf waters of the southwest coast of Arabian Sea, India for the characterization of photoprotective compounds in the zooplankton community. The study revealed the presence of photoprotective compounds, such asporphyra and palythine in the zooplankton community of all the stations, in addition to mycosporine glycine, in the polluted waters of the stations,Veli, Neendakari and Cochin.

Effects of ultraviolet radiation on the growth, reproduction and survival of the lobate ctenophore Mnemiopsis leidyi in Chesapeake Bay

Solar ultraviolet radiation (UVR) is an environmental stressor that can have a variety of negative effects on aquatic organisms including slowed growth, changes in reproduction and increased mortality. The ctenophore Mnemiopsis leidyi is a highly transparent organism that has not been shown to actively avoid ultraviolet radiation or possess photoprotective compounds and may therefore be vulnerable to deleterious effects of UVR. Results of this study indicate that summertime UVR exposure equivalent to average UVR conditions within the top 0.5m of the water column of the Rhode River, Maryland, USA, can cause mortality and reduced size of M. leidyi. Exposures tested did not, however, affect egg production beyond that attributable to UVR effects on mortality. Experiments indicated a sharp threshold for the tolerance of M. leidyi to biologically effective UVR exposure. A biological weighting function (BWF) was experimentally determined to describe the spectral dependence of UV induced mortality. The BWF was similar to those previously reported for mesozooplankton. M. leidyi is an important component of many ecosystems; thus, changes in its population size and abundance have the potential to significantly affect coastal and estuarine food webs, and oyster, fish and sea nettle populations, in systems like Chesapeake Bay. Future scenarios of decreased eutrophication and runoff that result in reduced dissolved organic matter and particulates, will likely lead to increased amounts and penetration of UVR in coastal and estuarine systems and could increase deleterious effects of UVR on M. leidyi.