To cope with environmental fluctuations and to prevent invasion by pathogens, plant metabolism must be flexible and dynamic. Active oxygen species, whose formation is accelerated under stress conditions, must be rapidly processed if oxidative damage is to be averted. The lifetime of active oxygen species within the cellular environment is determined by the antioxidative system, which provides crucial protection against oxidative damage. The antioxidative system comprises numerous enzymes and compounds of low molecular weight. While research into the former has benefited greatly from advances in molecular technology, the pathways by which the latter are synthesized have received comparatively little attention. The present review emphasizes the roles of ascorbate and glutathione in plant metabolism and stress tolerance. We provide a detailed account of current knowledge of the biosynthesis, compartmentation, and transport of these two important antioxidants, with emphasis on the unique insights and advances gained by molecular exploration.

ASCORBATE AND GLUTATHIONE: Keeping Active Oxygen Under Control

Drought-induced responses of photosynthesis and antioxidant metabolism in higher plants

Glutathione has numerous roles in cellular defence and in sulphur metabolism. These functions depend or impact on the concentration and/or redox state of leaf glutathione pools. Effective function requires homeostatic control of concentration and redox state, with departures from homeostasis acting as signals that trigger adaptive responses. Intercellular and intracellular glutathione pools are linked by transport across membranes. It is shown that glutathione can cross the chloroplast envelope at rates similar to the speed of biosynthesis. Control of glutathione concentration and redox state is therefore due to a complex interplay between biosynthesis, utilization, degradation, oxidation/reduction, and transport. All these factors must be considered in order to evaluate the significance of glutathione as a signalling component during development, abiotic stress, or pathogen attack.

Interactions between biosynthesis, compartmentation and transport in the control of glutathione homeostasis and signalling

summary The gradual but huge increase in atmospheric O # concentration that followed the evolution of oxygenic photosynthesis is one consequence that marks this event as one of the most significant in the earth’s history. The high redox potential of the O # }water couple makes it an extremely powerful electron sink that enables energy to be transduced in respiration. In addition to the tetravalent interconversion of O # and water, there exist a plethora of reactions that involve the partial reduction of O # or photodynamic energy transfer to produce active oxygen species (AOS). All these redox reactions have become integrated during evolution into the aerobic photosynthetic cell. This review considers photosynthesis as a whole-cell process, in which O # and AOS are involved in reactions at both photosystems, enzyme regulation in the chloroplast stroma, photorespiration, and mitochondrial electron transport in the light. In addition, oxidants and antioxidants are discussed as metabolic indicators of redox status, acting as sensors and signal molecules leading to acclimatory responses. Our aim throughout is to assess the insights gained from the application of mutagenesis and transformation techniques to studies of the role of O # and related redox components in the integrated regulation of photosynthesis.

https://nph.onlinelibrary.wiley.com/doi/pdf/10.1046/j.1469-8137.2000.00667.x

Tansley Review No. 112

Oxidative stress and antioxidant activity as the basis of senescence in maize leaves

The aim of this work was to determine the compartmentation of antioxidants between the bundle-sheath and mesophyll cells of maize (Zea mays L.) leaves. Rapid fractionation of the mesophyll compartment was used to minimize modifications in the antioxidant status and composition due to extraction procedures. The purity of the mesophyll isolates was assessed via the distribution of enzyme and metabolite markers. Ribulose-1,5 bisphosphate and ribulose-1,5-bisphosphate carboxylase/oxygenase were used as bundle-sheath markers and phosphoenolpyruvate carboxylase was used as the mesophyll marker enzyme. Glutathione reductase and dehydroascorbate reductase were almost exclusively localized in the mesophyll tissue, whereas ascorbate, ascorbate peroxidase, and superoxide dismutase were largely absent from the mesophyll fraction. Catalase, reduced glutathione, and monodehydroascorbate reductase were found to be approximately equally distributed between the two cell types. It is interesting that, whereas H2O2 levels were relatively high in maize leaves, this oxidant was largely restricted to the mesophyll compartment. We conclude that the antioxidants in maize leaves are partitioned between the two cell types according to the availability of reducing power and NADPH and that oxidized glutathione and dehydroascorbate produced in the bundle-sheat tissues have to be transported to the mesophyll for re-reduction to their reduced forms.

Differential Localization of Antioxidants in Maize Leaves

Separation of plant membrane lipids by multiple solid-phase extraction

Forest species in the course of their evolution have experienced several environmental challenges, which since historic times include anthropogenic pollution. The effects of pollution on the genetic and epigenetic diversity in black pine (Pinus nigra) forests were investigated in the Amyntaio – Ptolemais – Kozani Basin, which has been for decades the largest lignite mining and burning center of Greece, with a total installed generating capacity of about 4.5 GW, operating for more than 70 years and resulting in large amounts of primary air pollutant emissions, mainly SO2, NOx and PM10. P. nigra, a biomarker for air pollution and a keystone species of affected natural ecosystems, was examined in terms of phenology (cone and seed parameters), genetics (283 AFLP loci) and epigenetics (606 MSAP epiloci), using two populations (exposed to pollution and control) of the current (mature trees) and future (embryos) stand. It was found that cone, seed, as well as genetic diversity parameters, did not show statistically significant differences between the exposed population and the control. Nevertheless, statistically significant differences were detected at the population epigenetic level. Moreover, there was a further differentiation regarding the intergenerational comparison: while the epigenetic diversity does not substantially change in the two generations assessed in the control population, epigenetic diversity is significantly higher in the embryo population compared to the parental stand in the exposed population. This study sheds a light to genome dynamics in a forest tree population exposed to long term atmospheric pollution burden and stresses the importance of assessing both genetics and epigenetics in biomonitoring applications.

https://www.frontiersin.org/articles/10.3389/fpls.2023.1139331/pdf

Genetics and epigenetics of Pinus nigra populations with differential exposure to air pollution


 Grapevine (Vitis vinifera L.) is a major worldwide crop of high economic importance, tightly interwoven with the traditions and the culture of many civilizations. The Greek vineyard is one of the oldest in the world composed of an ample number of highly diverse indigenous landraces. However, over the last decades the local cultivated grapevine germplasm has undergone a drastic reduction of diversity, due to the established market preferences for international varieties. In the current work a combined approach involving both, ampelographic traits and microsatellite markers has been undertaken, to study the genetic diversity within and among 96 grapevine genotypes belonging to 36 V. vinifera subsp. vinifera cultivars, predominantly representing autochthonous Greek landraces. Results revealed high genetic diversity for the Greek cultivars yielding a mean number of alleles per locus 14.69 and mean polymorphic information content 0.848. Hierarchical cluster analysis, employing both, ampelographic and microsatellite data, showed a clear distinction based on the origin of the germplasm; Anatolian versus Mediterranean. Principal component analysis, based on the most informative ampelographic traits, coupled to the results from genetic structure analysis further corroborated the proposal of germplasm differentiation on the basis of geographic origin. This information can be further utilized for the reconstitution of the Greek vineyard and can significantly contribute towards a rational conservation and utilization strategy for breeding or for direct cultivation of the Greek indigenous grapevine germplasm.

Genetic diversity of Greek grapevine (Vitis vinifera L.) cultivars using ampelographic and microsatellite markers

Vitis vinifera ssp. vinifera (domesticated grapevine) includes thousands of cultivars, which are classified according to their main uses, as wines, fresh fruits or dried raisins and sultanas since ancient times. Evidence showed that Crete grapevine cultivars and winemaking date back to 2300 BC. In this study, fifty-one genotypes belonging to seven different traditional Vitis vinifera cultivars, presumed autochthonous to the island of Crete, were selected for their wine-producing potential and classified by 51 ampelographic descriptors. In addition, five genotypes belonging to two non-autochthonous cultivars were included as out-group controls. Subsequently, in order to characterize genetic diversity, establish genetic relationships within and between cultivars and solve accession-labeling problems, genotypes were fingerprinted employing Simple Sequence Repeat (SSR or microsatellite) markers. Four of the autochthonous cultivars namely ‘Vidiano’, ‘Vilana’, ‘Plyto’, and ‘Moschato Spinas’ are used in the local economy for blanc (white) wine production while the rest, namely ‘Kotsifali’, ‘Liatiko’ and ‘Mantilari’ for Noir (red) wines. The two cultivars employed as out-group were ‘Moschato Samou’ and ‘Moschato Alexandrias’: both white wine producers. Ampelography-based clustering grouped the majority of genotypes along cultivar-specific clusters. All three Moschato cultivars formed a distinct clade pointing to the non-autochthonous origin of ‘Moschato Spinas’. A total of one hundred and thirteen (113) SSR alleles were amplified from thirteen (13) SSR loci, with an average number of alleles per locus equal to 10.23 revealing ample genetic polymorphism. The cumulative probability of identity was also quite high (3.389 × 10−16). The overall observed heterozygosity was 0.837 while for twenty-nine of the examined genotypes, at least one private SSR allele was detected. The majority of genotypes were grouped in cultivar-specific clusters. The results of this paper pave the way for the certification and registration of clones of some of the most important wine-producing cultivars in Crete.

/pdf/analysis-of-wine-producing-vitis-vinifera-l-biotypes-172yn118.pdf

Andreas Doulis

Papers

Differential Localization of Antioxidants in Maize Leaves

Separation of plant membrane lipids by multiple solid-phase extraction

Genetics and epigenetics of Pinus nigra populations with differential exposure to air pollution

Genetic diversity of Greek grapevine (Vitis vinifera L.) cultivars using ampelographic and microsatellite markers

Analysis of Wine-Producing Vitis vinifera L. Biotypes, Autochthonous to Crete (Greece), Employing Ampelographic and Microsatellite Markers