The non-foliar hypoxic photosynthetic syndrome: evidence for enhanced pools and functionality of xanthophyll cycle components and active cyclic electron flow in fruit chlorenchyma

Seasonal Differences in Leaf Photoprotective Potential between Adults and Juveniles of Two Mediterranean Perennials with Distinct Growth Forms: A Comparative Field Study

The photosynthetic differences between adult and juvenile Mediterranean plants were previously studied under field conditions, yet the corresponding differentiation of their photoprotective efficiency has not been sufficiently investigated. The present study aims to examine possible differences in the photoprotective potential between adults and juveniles of two native Mediterranean plants with distinct growth forms. Thus, the seasonal variations in individual carotenoids, electron transport rate (ETR), and non-photochemical quenching (NPQ) were monitored in fully exposed mature leaves from adults and juveniles of the winter deciduous tree Cercis siliquastrum L. and the evergreen sclerophyllous shrub Nerium oleander L. All plants were grown under apparently similar field conditions. In both species, juveniles displayed substantially lower ETR and increased NPQ values than adults in spring, with the differences intensifying during summer drought and diminishing in autumn. Concomitantly, juveniles showed significantly higher chlorophyll-based total carotenoids in spring and summer mainly due to the higher investment in xanthophyll cycle components (VAZ), in combination with an increased mid-day de-epoxidation state (DEPS) and partial retention of zeaxanthin in the dark. In N. oleander, although ETR was lower in juveniles during winter, NPQ was extremely low in both ages. In conclusion, juveniles exhibit enhanced photoprotection potential, especially in the summer, due to their reduced photochemical capacity. The photosynthetic superiority of adults during the favorable spring period may be attributed to the needs of the co-existing reproductive effort.

Beneficial properties of Drimia numidica leaf methanolic extract against the cytogenotoxic effects of mitomycin C on human lymphocytes

This study investigated the phytochemical profile of Drimia numidica leaf methanolic extract, as well as its cyto-genotoxic and cyto/genoprotective potential against mitomycin C (MMC) mediated effects on healthy human lymphocytes. Photosynthetic pigments, trace elements, and secondary metabolites were estimated and/or identified in methanolic extract of mature leaves, and the latter was further used for assessing its in vitro biological effects on MMC-free and/or MMC-treated human lymphocytes (at low, non-toxic concentrations of 0.001 and 0.01% v/v). The results showed that D. numidica leaf methanolic extract, being rich in carotenoids, phenolics, flavonoids, organic acids and bufadienolides, could be protective against MMC mediated cyto/genotoxic potential in healthy human lymphocytes. Biomolecules possessing antioxidant and antitumor potential, such as beta-carotene and lutein among others, chlorogenic acid, caffeic acid and their derivatives, minerals such as Si, as well as apigenin- and luteolin-derived glycosides, either individual or in a mixture, could be beneficial rather than harmful, at least at the extract concentrations tested. Although further in vitro and in vivo studies are still needed for elucidating the beneficial (individual and/or additive/synergistic) role of those compounds, the results of the present study are quite promising, thus encouraging new challenges for the appropriate utilization of D. numidica leaf extract.

The Transcriptional Responses and Metabolic Consequences of Acclimation to Elevated Light Exposure in Grapevine Berries

An increasing number of field studies that focus on grapevine berry development and ripening implement systems biology approaches; the results are highlighting not only the intricacies of the developmental programming/reprogramming that occurs, but also the complexity of how profoundly the microclimate influences the metabolism of the berry throughout the different stages of development. In a previous study we confirmed that a leaf removal treatment to Sauvignon Blanc grapes, grown in a highly characterized vineyard, primarily affected the level of light exposure to the berries throughout their development. A full transcriptomic analysis of berries from this model vineyard details the underlying molecular responses of the berries in reaction to the exposure and show how the berries acclimated to the imposing light stress. Gene expression involved in the protection of the photosynthetic machinery through rapid protein-turnover and the expression of photoprotective flavonoid compounds were most significantly affected in green berries. Overall, the transcriptome analysis showed that the berries implemented multiple stress-mitigation strategies in parallel and metabolite analysis was used to support the main findings. Combining the transcriptome data and amino acid profiling provided evidence that amino acid catabolism probably contributed to the mitigation of a likely energetic deficit created by the upregulation of (energetically) costly stress defense mechanisms. Furthermore, the rapid turnover of essential proteins involved in the maintenance of primary metabolism and growth in the photosynthetically active grapes appeared to provide precursors for the production of protective secondary metabolites such as apocarotenoids and flavonols in the ripening stages of the berries. Taken together, these results confirmed that the green grape berries responded to light stress much like other vegetative organs and were able to acclimate to the increased exposure, managing their metabolism and energy requirements to sustain the developmental cycle toward ripening. The typical metabolic consequences of leaf removal on grape berries can therefore now be linked to increased light exposure through mechanisms of photoprotection in green berries that leads toward acclimation responses that remain intact until ripening.