Transcriptional Regulation of Vitamin E Biosynthesis during Germination of Dwarf Fan Palm Seeds.

Vitamin E, a potent antioxidant either presents in the form of tocopherols and/or tocotrienols depending on the plant species, tissue and developmental stage, plays a major role in protecting lipids from oxidation in seeds. Unlike tocopherols, which have a more universal distribution, the occurrence of tocotrienols is limited primarily to monocot seeds. Dwarf fan palm (Chamaerops humilis var.

Enhanced tocopherol levels during early germination events in Chamaerops humilis var. humilis seeds.

Most angiosperms accumulate vitamin E in the form of tocopherols in seeds, exerting a protective antioxidant role. However, several palm trees principally accumulate tocotrienols, rather than tocopherols, in seeds, as it occurs in other monocots. To unravel the protective role of either tocopherols or tocotrienols against lipid peroxidation during seed germination in Chamaerops humilis var.

Redox proteomics and physiological responses in Cistus albidus shrubs subjected to long-term summer drought followed by recovery.

The interaction between enzymatic and non-enzymatic antioxidants, endogenous levels of ABA and ABA-GE, the rapid recuperation of photosynthetic proteins under re-watering as well the high level of antioxidant proteins in previously drought-stressed plants under re-watering conditions, will contribute to drought resistance in plants subjected to a long-term drought stress under Mediterranean field conditions. This work provides an overview of the mechanisms of Cistus albidus acclimation to long-term summer drought followed by re-watering in Mediterranean field conditions. To better understand the molecular mechanisms of drought resistance in these plants, a proteomic study using 2-DE and MALDI-TOF/TOF MS/MS was performed on leaves from these shrubs.

Assessing the regulation of leaf redox status under water stress conditions in Arabidopsis thaliana: Col-0 ecotype (wild-type and vtc-2), expressing mitochondrial and cytosolic roGFP1.

Using Arabidopsis plants Col-0 and vtc2 transformed with a redox sensitive green fluorescent protein, (c-roGFP) and (m-roGFP), we investigated the effects of a progressive water stress and re-watering on the redox status of the cytosol and the mitochondria. Our results establish that water stress affects redox status differently in these two compartments, depending on phenotype and leaf age, furthermore we conclude that ascorbate plays a pivotal role in mediating redox status homeostasis and that Col-0 Arabidopsis subjected to water stress increase the synthesis of ascorbate suggesting that ascorbate may play a role in buffering changes in redox status in the mitochondria and the cytosol, with the presumed buffering capacity of ascorbate being more noticeable in young compared with mature leaves. Re-watering of water-stressed plants was paralleled by a return of both the redox status and ascorbate to the levels of well-watered plants.

Plant aging and excess light enhance flavan-3-ol content in Cistus clusii.

Physiological studies on aging in perennials are mainly focused either on the primary metabolism or the hormonal regulation of the process. However, to our knowledge, the involvement of the secondary metabolism in this process has not yet been explored. Cistus clusii, a Mediterranean sclerophyllous evergreen bush, shows considerable amounts of flavan-3-ols in leaves.

How relevant are flavonoids as antioxidants in plants?

Flavonoids are a large family of plant secondary metabolites, principally recognized for their health-promoting properties in human diets. Most flavonoids outperform well-known antioxidants, such as ascorbate (vitamin C) and alpha-tocopherol (vitamin E), in in vitro antioxidant assays because of their strong capacity to donate electrons or hydrogen atoms. However, experimental evidence for an antioxidant function in plants is limited to a few individual flavonoids under very specific experimental and developmental conditions.

Hydrogen peroxide is involved in the acclimation of the Mediterranean shrub, Cistus albidus L., to summer drought.

This study evaluated the possible role of hydrogen peroxide (H(2)O(2)) in the acclimation of a Mediterranean shrub, Cistus albidus L., to summer drought growing under Mediterranean field conditions. For this purpose, changes in H(2)O(2) concentrations and localization throughout a year were analysed.

Alpha-tocopherol may influence cellular signaling by modulating jasmonic acid levels in plants.

Most studies on the function of tocopherols in plants have focused on their photo-protective and antioxidant properties, and it has been recently suggested, though not yet demonstrated, that they may also play a role in cellular signaling. By using vte1 mutants of Arabidopsis thaliana, with an insertion in the promoter region of the gene encoding tocopherol cyclase, we demonstrate here for the first time that tocopherol deficiency may alter endogenous phytohormone levels in plants, thereby reducing plant growth and triggering anthocyanin accumulation in leaves. In plants grown under a combination of high light and low temperature conditions to induce anthocyanin accumulation, we evaluated age-dependent changes in tocopherols, indicators of photo-oxidative stress, phytohormone levels, plant growth and anthocyanin levels in wild type and vte1 mutants.

Enhanced oxidation of flavan-3-ols and proanthocyanidin accumulation in water-stressed tea plants.

(-)-Epicatechin (EC) and (-)-epigallocatechin gallate (EGCG), two major tea flavan-3-ols, have received attention in food science and biomedicine because of their potent antioxidant properties. In plants, flavan-3-ols serve as proanthocyanidin (PA) building blocks, and although both monomeric flavan-3-ols and PAs show antioxidant activity in vitro, their antioxidant function in vivo remains unclear. In the present study, EC quinone (ECQ) and EGCG quinone (EGCGQ), the oxidation products of EC and EGCG, increased up to 100- and 30-fold, respectively, in tea plants exposed to 19 days of water deficit.

Enhanced alpha-tocopherol quinone levels and xanthophyll cycle de-epoxidation in rosemary plants exposed to water deficit during a Mediterranean winter.

Photosynthesis operates in a constantly shifting balance between efficient capture of solar energy and its rapid dissipation when captured in excess. In an attempt to better understand the role of alpha-tocopherol in plant photoprotection, we examined the changes in alpha-tocopherol quinone (alpha-TQ), in parallel with those of other low-molecular-weight antioxidants, in rosemary plants exposed to water deficit during a Mediterranean winter. Relative leaf water content (RWC) decreased from about 85% to approximately 65% in drought, but plants did not show symptoms of oxidative damage, as indicated by constant Fv/Fm ratios and malondialdehyde (MDA) levels.

Drought-induced changes in flavonoids and other low molecular weight antioxidants in Cistus clusii grown under Mediterranean field conditions.

Mediterranean plants have evolved a complex antioxidant defense system to cope with summer drought. Flavonoids, and particularly flavanols and flavonols, are potent in vitro antioxidants, but their in vivo significance within the complex network of antioxidant defenses remains unclear, especially in plant responses to stress. To gain insight into the role of flavonoids in the antioxidant defense system of Cistus clusii Dunal, we evaluated drought-induced changes in flavonoids in leaves and compared the response of these compounds with that of other low molecular weight antioxidants (ascorbic acid, tocopherols and carotenoids).

Die and let live: leaf senescence contributes to plant survival under drought stress.

Leaf senescence is a highly regulated physiological process that leads to leaf death and is, as such, the last developmental stage of the leaf. Plant aging and environmental stresses may induce the process of senescence. Here we will focus on the role of leaf senescence in field-grown plants as a response to adverse climatic conditions and, more specifically, on how it contributes to plant survival under drought stress.

Drought-induced changes in the redox state of alpha-tocopherol, ascorbate, and the diterpene carnosic acid in chloroplasts of Labiatae species differing in carnosic acid contents.

To assess antioxidative protection by carnosic acid (CA) in combination with that of other low-molecular weight (M(r)) antioxidants (alpha-tocopherol [alpha-T] and ascorbate [Asc]) in chloroplasts, we measured endogenous concentrations of these antioxidants, their redox states, and other indicators of oxidative stress in chloroplasts of three Labiatae species, differing in their CA contents, exposed to drought stress in the field. Damage to the photosynthetic apparatus was observed neither in CA-containing species (rosemary [Rosmarinus officinalis]) and sage [Salvia officinalis]) nor in CA-free species (lemon balm [Melissa officinalis]) at relative leaf water contents between 86% and 58%, as indicated by constant maximum efficiency of photosystem II photochemistry ratios and malondialdehyde levels in chloroplasts. The three species showed significant increases in alpha-T, a shift of the redox state of alpha-T toward its reduced state, and increased Asc levels in chloroplasts under stress.

Enhanced photo- and antioxidative protection, and hydrogen peroxide accumulation in drought-stressed Cistus clusii and Cistus albidus plants.

Mechanisms of drought stress resistance were studied in Cistus clusii Dunal and Cistus albidus L., two native Mediterranean shrubs that can withstand severe summer drought. While water deficit, solar radiation and temperature increased from winter to summer in the field, C.

Interplay between ascorbic acid and lipophilic antioxidant defences in chloroplasts of water-stressed Arabidopsis plants.

The effects of low ascorbic acid (Asc) on lipophilic antioxidant defences and lipid peroxidation in chloroplasts were evaluated in the vtc-1 mutant of Arabidopsis thaliana, which had an Asc deficiency in chloroplasts of ca. 60%. Although low Asc did not cause oxidative stress in optimal growth conditions, it increased malondialdehyde levels in chloroplasts by ca.

Effect of drought and high solar radiation on 1-aminocyclopropane-1-carboxylic acid and abscisic acid concentrations in Rosmarinus officinalis plants.

The endogenous concentrations of ACC and ABA were measured, at predawn and at maximum solar radiation, during a summer drought, and recovery after autumn rainfalls, in rosemary (Rosmarinus officinalis L.), a drought-tolerant species, growing under Mediterranean field conditions. During the summer, plants were subjected to both water deficit and high solar radiation.

An increase in water deficit has no impact on the photosynthetic capacity of field-grown Mediterranean plants.

In the Mediterranean, annual mean precipitation has continuously decreased over the last three years (by ca 36% in Barcelona), and the decrease has been dramatic during the summer (by ca 78 and 64% during July and August, respectively). The impact of increased drought on the photosynthetic capacity of Mediterranean vegetation is currently unknown. In this study, two native Mediterranean plants [rosemary (Rosmarinus officinalis L.