Solar ultraviolet radiation is necessary to enhance grapevine fruit ripening transcriptional and phenolic responses

Background: Ultraviolet (UV) radiation modulates secondary metabolism in the skin of Vitis vinifera L. berries, which affects the final composition of both grapes and wines. The expression of several phenylpropanoid biosynthesis-related genes is regulated by UV radiation in grape berries. However, the complete portion of transcriptome and ripening processes influenced by solar UV radiation in grapes remains unknown.Results: Whole genome arrays were used to identify the berry skin transcriptome modulated by the UV radiation received naturally in a mid-altitude Tempranillo vineyard. UV radiation-blocking and transmitting filters were used to generate the experimental conditions. The expression of 121 genes was significantly altered by solar UV radiation. Functional enrichment analysis of altered transcripts mainly pointed out that secondary metabolism-related transcripts were induced by UV radiation including VvFLS1, VvGT5 and VvGT6 flavonol biosynthetic genes and monoterpenoid biosynthetic genes. Berry skin phenolic composition was also analysed to search for correlation with gene expression changes and UV-increased flavonols accumulation was the most evident impact. Among regulatory genes, novel UV radiation-responsive transcription factors including VvMYB24 and three bHLH, together with known grapevine UV-responsive genes such as VvMYBF1, were identified. A transcriptomic meta-analysis revealed that genes up-regulated by UV radiation in the berry skin were also enriched in homologs of Arabidopsis UVR8 UV-B photoreceptor-dependent UV-B -responsive genes. Indeed, a search of the grapevine reference genomic sequence identified UV-B signalling pathway homologs and among them, VvHY5-1, VvHY5-2 and VvRUP were up-regulated by UV radiation in the berry skin.Conclusions: Results suggest that the UV-B radiation-specific signalling pathway is activated in the skin of grapes grown at mid-altitudes. The biosynthesis and accumulation of secondary metabolites, which are appreciated in winemaking and potentially confer cross-tolerance, were almost specifically triggered. This draws attention to viticultural practices that increase solar UV radiation on vineyards as they may improve grape features. © 2014 Carbonell-Bejerano et al.; licensee BioMed Central Ltd

Moss communities in the irrigation channels of the river Iregua basin (La Rioja, northern Spain)

Nineteen bryophytes (all of them mosses), one alga and seven vascular plants were found in 26 irrigation channels of the river Iregua basin (La Rioja, northern Spain), a kind of aquatic environment not previously investigated regarding bryophytes. The species richness, the cover, and the Shannon's diversity (when calculated including bare soil - areas with no bryophyte - as an additional "species") of the communities were correlated negatively with the dryness period in the channels, and positively with the water flow and velocity. Hence, high values of those variables were found in refuge sites, such as the main control-gates through which the river water enters the irrigation channels, whereas low values were typical of frequently dry terminal channels. The diversity values were comparable to those found in the lower course of rivers (which might be systems equally adverse for bryophytes), but only half of those recorded for streams. In the canonical correspondence analysis (CCA), Cratoneuron filicinum and Rynchostegium riparioides prevailed in channels with a higher water availability, whereas Amblystegium riparium was dominant in channels with harder waters and slower currents. A wider spatial sampling, including different channel types and systems, would be needed to analyse the usefulness of bryophytes as bioindicators of the water quality in irrigation channels

Seasonal variations in UV-absorbing compounds and physiological characteristics in the aquatic liverwort Jungermannia exsertifolia subsp. cordifolia over a three-year period

Temporal physiological variations in relation to environmental factors, in particular to ultraviolet (UV) radiation, have been studied in bryophytes from circumpolar latitudes, but not in mid-latitudes with longer growing seasons. In addition, seasonal and interannual changes in individual UV-absorbing compounds (UVAC) have not been previously studied in bryophytes. To fill these gaps, samples of the aquatic liverwort Jungermannia exsertifolia subsp. cordifolia were collected on a monthly basis during 3 years from a mountain stream in northern Spain. Sclerophylly index, chlorophyll fluorescence, DNA damage, the bulk UV absorbance of methanolic extracts and the concentration of five UVAC (hydroxycinnamic acid derivatives) were measured. Interannual changes were little marked, probably because the 3 years studied were environmentally similar. In summer-autumn, with respect to seasonal variations, newly grown tender young shoots with high Fv/Fm accumulated higher amounts of several hydroxycinnamic acid derivatives than in winter-spring. DNA damage was not detected in any of the samples analyzed. p-Coumaroylmalic acid was the compound best associated with radiation changes, and the best model explaining UV-B took into consideration the concentration of this compound and the ozone level. The specific effects of UV radiation could not be separated from the effects caused by other environmental factors, such as global radiation or temperature, because all these variables were correlated. However, indirect evidence strongly suggests that seasonal changes in bulk UV absorbance and p-coumaroylmalic acid are mainly driven by UV radiation. This compound may be a promising physiological variable to be used for UV bioindication. Copyright © 2009 Physiologia Plantarum

Cell compartmentation of ultraviolet-absorbing compounds: An underexplored tool related to bryophyte ecology, phylogeny and evolution

Excessive exposure to ultraviolet (UV) radiation can be harmful to photosynthetic organisms, that most frequently respond with the accumulation of protective UV-absorbing compounds (UVACs). UVACs location in different cell compartments can influence their preferential protective role as antioxidants and/or UV screens. However, the phylogenetic, ecological and evolutionary implications of UVACs compartmentation has been little studied, particularly in bryophytes. We analysed UVACs in the methanol-soluble and -insoluble fractions (SUVACs and IUVACs respectively) in extracts of 87 bryophytes belonging to their three evolutionary lineages: 22 liverworts, 64 mosses and one hornwort. Assuming that the cell wall-bound IUVACs are more effective UV screens than the mainly vacuolar SUVACs, thus conferring a higher UV tolerance, we evaluated whether UVACs levels and compartmentation were related to: (1) the bryophyte phylogeny down to the Order level; and (2) the bryophyte ecological attributes, including sun exposure and Ellenberg indicator values (numerical system classifying species' habitat along gradients of environmental factors). A similar phylogenetic and ecological analysis was conducted on the sclerophylly index (the ratio between the dry mass and the surface area of the bryophyte shoot). Mosses showed lower SUVACs but higher IUVACs and total UVACs, together with higher IUVAC/SUVAC ratios, than liverworts. Thus, mosses would better tolerate UV radiation than liverworts, which matches well with their general ecological preferences. As bryophytes were the earliest diverging land plants, we could infer that the different UVACs compartmentation between mosses and liverworts could have influenced their ecological segregation upon plant land colonization. UVACs compartmentation also differed between the two major moss lineages (acrocarpous and pleurocarpous), while the anatomically peculiar Sphagnales were the best characterized Order. There were not solid relationships between UVACs and the ecological attributes considered. Hence, UVACs might be mainly constitutive in bryophytes, depending more on the species phylogeny than on the habitat occupied in nature. Liverworts were less sclerophyllous than mosses, and, as in tracheophytes, water restrictions and high sun exposures increased sclerophylly. In conclusion, UVACs compartmentation represents an ecophysiological trait useful to understand the bryophyte ecophylogeny, because different compartmentation modalities seem to imply different UV adaptations and tolerance. A plain language summary is available for this article. © 2018 British Ecological Society

Effects of enhanced ultraviolet radiation on six aquatic bryophytes

Six aquatic bryophytes, three liverworts (Jungermannia exsertifolia subsp. cordifolia, Marsupella sphacelata and Scapania undulatd) and three mosses (Brachythecium rivulare, Bryum pseudotriquetrum and Racomitrium aciculare) were cultured in the laboratory under artificially enhanced ultraviolet-B (UV-B) radiation to evaluate their physiological responses to a potential ozone depletion. The daily-integrated biologically-effective UV-B irradiance applied was 10.3 kJ m-2 (as estimated using the generalized plant damage action spectrum), mimicking a 20% ozone depletion at the latitude of the sampling site. Photosynthetic pigment composition, some variables of chlorophyll fluorescence, sclerophylly, the amount of methanol-extractable UV-absorbing compounds, and growth, were measured after 20 days of culture. The physiology of bryophytes was overall more influenced by the culture conditions than by the UV treatment, and the responses to both factors depended on the species and the variable considered. The culture conditions affected negatively some basic physiological variables (e.g. photosynthetic pigments and photosynthetic performance), especially in some species, but these adverse effects did not impede growth (except in Marsupella sphacelata). Enhanced UV-B affected negatively only some pigment variables, but not the photosynthetic performance (as derived from chlorophyll fluorescence variables) nor growth (except in Jungermannia exsertifolia subsp. cordifolia). The increase in UV-protective compounds under enhanced UV-B was rare. It may be concluded that the species studied were UV-B tolerant under the conditions considered in the present work, probably due to the fact that the samples were naturally well acclimated to high UV-B levels because they were collected at high altitudes (1850-2000 m) and near the summer solstice. Thus, they would not need additional protection against the UV-B levels used in the laboratory culture. The responses to enhanced UV-B may not depend only on the species and the environmental conditions, as it had been pointed out before, but also on the collection site and the collection date of the samples. © 2009 Adac. Tous droits réservés

Ultraviolet radiation-induced changes in mycosporine-like amino acids and physiological variables in the red alga Lemanea fluviatilis

Samples of Lemanea fluviatilis were cultured in the laboratory under three different radiation regimes, which included the absence and presence of ultraviolet (UV) radiation. Photosynthetic pigment composition, photosynthetic activity, and mycosporine-like amino acids (MAAs) were analyzed after 16 and 64 h of exposure to the radiation. Two MAAs were identified as porphyra-334 and mycosporine-glycine. Mycosporine-glycine was specifically induced by UV-B radiation, but porphyra-334 was degraded by this radiation. The level of UV irradiance used in the induction experiment produced damages in the alga as revealed by reductions in photosynthetic activity and photosynthetic pigments (chlorophyll, phycocyanin, and total carotenoids). Our results indicate that the MAAs failed to fully protect the photosynthetic machinery against UV-B under the specific conditions used in this study

Cell compartmentation of UV-absorbing compounds in two aquatic mosses under enhanced UV-B

The effects of enhanced UV-B radiation on UV-absorbing compounds (UVAC), the maximum quantum yield of photosystem II (Fv/Fm), DNA integrity, and the sclerophylly index, were analyzed in the mosses Bryum pseudotriquetrum and Fontinalis antipyretica. The study was performed for 31 days under laboratory conditions. Enhanced UV-B increased the bulk level of the vacuolar soluble UVAC (SUVAC) in both mosses and the concentration of two different soluble kaempferols in B. pseudotriquetrum. However, enhanced UV-B had no effect on the bulk level of cell wall-bound insoluble UVAC (WUVAC) in both mosses and the concentration of insoluble p-coumaric acid in F. antipyretica. Thus, the insoluble fraction would be less UV-B-responsive than the soluble one. This probably happened because (1) the constitutively high bulk level of WUVAC (and noticeably higher than that of SUVAC) would already provide a sufficiently effective protection; and (2) WUVAC would be relatively immobilized in the cell wall, which would limit the reaction capacity of these compounds to UV-B. The protective mechanisms developed by both mosses could not totally prevent UV-B damage, which was indicated by the modest decrease of Fv/F m and the increase in DNA damage. We discuss the ecological and phylogenetic implications of the differences in UVAC compartmentation between liverworts and mosses. © 2012 Adac. Tous droits réservés