Pre- and post-melatonin mitigates the effect of ionizing radiation-induced damage in wheat by modulating the antioxidant machinery.

As an indolamine, melatonin (C13H16N2O2) performs essential roles in the regulation of plant growth and development and ameliorates the harmful effects of abiotic stresses. This study examined two types of melatonin application, pre-sowing (prMel) and application during growth (ptMel), in wheat (Triticum aestivum L.) seedlings exposed to four different doses (100, 200, 300, and 400 Gy) of radioactive cobalt (60Co) gamma rays as dry seeds to investigate their ameliorative effects on ionizing radiation (IR) stress. Peroxidase, catalase, superoxide dismutase, ascorbate peroxidase, glutathione reductase, mono- and dihydroxyperoxidase, and phenylalanine ammonia-lyase activities, and levels of lipid peroxidation, H2O2, and total glutathione (GSH), and phenolic acids (PHAs) in soluble free, ester, glycoside and ester-bound forms were examined in the seedlings. Both melatonin applications were found to increase lipid peroxidation, H2O2, and GSH contents previously reduced by gamma irradiation. The IR treatment-induced increases in enzyme activities were significantly reduced by melatonin applications. The study findings indicated that high doses of IR resulted in significant decreases in the activity and levels of the measured traits. The predominant PHAs in the tissues were vanillic, ferulic, and p-coumaric acids. In addition, ptMel application combined with IR stress lowered the total phenolic acid contents in the soluble forms while increasing those in the cell wall-bound form. In conclusion, the antioxidant system in the seedlings exposed to the different gamma ray doses was regulated by prMel and ptMel applications in such a manner as to alleviate IR stress-induced oxidatives damages in the wheat.

Cryo-EM structure of a plant photosystem II supercomplex with light-harvesting protein Lhcb8 and α-tocopherol.

The heart of oxygenic photosynthesis is the water-splitting photosystem II (PSII), which forms supercomplexes with a variable amount of peripheral trimeric light-harvesting complexes (LHCII). Our knowledge of the structure of green plant PSII supercomplex is based on findings obtained from several representatives of green algae and flowering plants; however, data from a non-flowering plant are currently missing. Here we report a cryo-electron microscopy structure of PSII supercomplex from spruce, a representative of non-flowering land plants, at 2.8 Å resolution. Compared with flowering plants, PSII supercomplex in spruce contains an additional Ycf12 subunit, Lhcb4 protein is replaced by Lhcb8, and trimeric LHCII is present as a homotrimer of Lhcb1. Unexpectedly, we have found α-tocopherol (α-Toc)/α-tocopherolquinone (α-TQ) at the boundary between the LHCII trimer and the inner antenna CP43. The molecule of α-Toc/α-TQ is located close to chlorophyll a614 of one of the Lhcb1 proteins and its chromanol/quinone head is exposed to the thylakoid lumen. The position of α-Toc in PSII supercomplex makes it an ideal candidate for the sensor of excessive light, as α-Toc can be oxidized to α-TQ by high-light-induced singlet oxygen at low lumenal pH. The molecule of α-TQ appears to shift slightly into the PSII supercomplex, which could trigger important structure-functional modifications in PSII supercomplex. Inspection of the previously reported cryo-electron microscopy maps of PSII supercomplexes indicates that α-Toc/α-TQ can be present at the same site also in PSII supercomplexes from flowering plants, but its identification in the previous studies has been hindered by insufficient resolution.

Phenylpropanoid Content of Chickpea Seed Coats in Relation to Seed Dormancy.

The physical dormancy of seeds is likely to be mediated by the chemical composition and the thickness of the seed coat. Here, we investigate the link between the content of phenylpropanoids (i.e., phenolics and flavonoids) present in the chickpea seed coat and dormancy. The relationship between selected phenolic and flavonoid metabolites of chickpea seed coats and dormancy level was assessed using wild and cultivated chickpea parental genotypes and a derived population of recombinant inbred lines (RILs). The selected phenolic and flavonoid metabolites were analyzed via the LC-MS/MS method. Significant differences in the concentration of certain phenolic acids were found among cultivated (Cicer arietinum, ICC4958) and wild chickpea (Cicer reticulatum, PI489777) parental genotypes. These differences were observed in the contents of gallic, caffeic, vanillic, syringic, p-coumaric, salicylic, and sinapic acids, as well as salicylic acid-2-O-ß-d-glucoside and coniferaldehyde. Additionally, significant differences were observed in the flavonoids myricetin, quercetin, luteolin, naringenin, kaempferol, isoorientin, orientin, and isovitexin. When comparing non-dormant and dormant RILs, significant differences were observed in gallic, 3-hydroxybenzoic, syringic, and sinapic acids, as well as the flavonoids quercitrin, quercetin, naringenin, kaempferol, and morin. Phenolic acids were generally more highly concentrated in the wild parental genotype and dormant RILs. We compared the phenylpropanoid content of chickpea seed coats with related legumes, such as pea, lentil, and faba bean. This information could be useful in chickpea breeding programs to reduce dormancy.

Evaluation of Halophyte Biopotential as an Unused Natural Resource: The Case of Lobularia maritima.

Halophytes are plant species widely distributed in saline habitats, such as beaches, postindustrial wastelands, irrigated lands, salt flats, and others. Excessive salt level, known to limit plant growth, is not harmful to halophytes, which have developed a variety of defense mechanisms allowing them to colonize harsh environments. Plants under stress are known to respond with several morpho-anatomical adaptations, but also to enhance the production of secondary metabolites to better cope with difficult conditions. Owing to these adaptations, halophytes are an interesting group of undemanding plants with a high potential for application in the food and pharmaceutical industries. Therefore, this review aims to present the characteristics of halophytes, describe changes in their gene expression, and discuss their synthesized metabolites of pharmacognostic and pharmacological significance. Lobularia maritima is characterized as a widely spread halophyte that has been shown to exhibit various pharmacological properties in vitro and in vivo. It is concluded that halophytes may become important sources of natural products for the treatment of various ailments and for supplementing the human diet with necessary non-nutrients and minerals. However, extensive studies are needed to deepen the knowledge of their biological potential in vivo, so that they can be introduced to the pharmaceutical and food industries.

Influence of Climate-Related Environmental Stresses on Economically Important Essential Oils of Mediterranean Salvia sp.

Salvia L. is the largest genus in the family Lamiaceae, with about 1,000 species and a nearly cosmopolitan distribution. Salvia species are used in both traditional and conventional medicines, and other numerous industries, such as spices and perfumes. The number of papers dealing with Salvia exceeds 12,000 and mostly investigates their chemical composition and bioactive properties. A smaller proportion of papers however consider environmental factors, mostly on the effects of microclimate conditions on its geographic distribution along an altitudinal or longitudinal gradient, and very few studies can be found on the effects of emerging stressors on the commercial production of sages of medicinal and economical importance. Here, we summarize available data on the essential oil composition of three economically important sages from the Mediterranean area, that is, Salvia officinalis, Salvia officinalis subsp. lavandulifolia, and Salvia fruticosa, and the effects of climate-related environmental stressors on their chemical profiles. Environmental stress factors, such as an increase in soil salinity and aridity, and changes in annual average temperatures, are going to impose a serious risk on the commercial production of sage essential oils, which are commercially produced in many European countries. This review highlights the already confirmed effects of these stressors on three selected Salvia species and consequently the importance of mitigating the effects of climate change on the commercial production of these essential oils.

Exploring New Sources of Bioactive Phenolic Compounds from Western Balkan Mountains.

This study presents the first report on phenolic composition and bioactivity of ethanolic extracts of three plant species that grow in the western Balkan mountains and are used in traditional folk medicine: Valeriana montana, Salix retusa, and Campanula hercegovina. Phenolics were extracted from different aerial plant parts using 80% ethanol to assess the possibility of sustainable use of these plants as a source of bioactive compounds without disruption to the roots (for V. montana) or destruction of whole habitats (for S. retusa and C. hercegovina). The ethanolic extract of V. montana flower contained noticeable levels of apigenin and quercetin. The branches and bark of S. retusa were significantly rich in catechin, while rutin was the major phenolic found in the leaf extract of C. hercegovina. Furthermore, the flower extract of V. montana revealed the best antioxidant activity, which was comparable to 4-hydroxybenzoic acid and quercetin. Considering antimicrobial activity, the leaf extracts of V. montana and C. hercegovina demonstrated potent activity against all microbes tested, while the extracts of S. retusa were moderately effective. The presented results emphasize the potential of these plants as novel sources of bioactive compounds.

Genotoxic and cytotoxic assessment of two endemic Lamiaceae species from Bosnia and Herzegovina.

Clinopodium alpinum subsp. orontium (K.Malý) Govaerts and Thymus bracteosus Vis. ex Benth. are endemic Lamiaceae species in Bosnia and Herzegovina with rather limited data about their cytotoxic and genotoxic effects. This study aimed to analyse phenolic compounds composition of C. alpinum subsp. orontium and T. bracteosus aqueous and dimethyl sulphoxide (DMSO) extracts and their cytotoxic and genotoxic potential in human peripheral blood lymphocyte cultures. Among 33 analytes, 17 were identified and quantified in the examined extracts with the rosmarinic and chlorogenic acids as main constituents. Genotoxic effects of extracts from both species are proven at the highest applied dose. T. bracteosus extracts and DMSO as a solvent exhibited stronger genotoxic potential that should be further investigated in tumour cell lines. Nevertheless, non-endemic species with similar phenolic composition and bioactivity should be the first choice for medicinal purposes.

Analytical methods in strigolactone research.

Strigolactones (SLs) are important plant hormones that are produced via the carotenoid biosynthetic pathway and occur at extremely low concentrations in various plant species. They regulate root development, play important roles in symbioses between higher plants and mycorrhizal fungi, and stimulate germination of plant-parasitic Orobanche and Striga species. Chemical analysis is central to research on the biochemistry of SLs and their roles in developmental biology and plant physiology. Here we summarize key issues relating to the identification and quantification of SLs isolated from plant tissues and exudates. The advantages and drawbacks of different protocols used for strigolactone analysis are discussed, and guidelines for selecting a procedure that will minimize losses during isolation and purification prior to final analysis are proposed. Hyphenated techniques suitable for SL analysis such as GC-MS and LC-MS/MS are also discussed, and newer ambient techniques such as HR-DART-MS and DESI-MS are highlighted as tools with considerable potential in SL research. A key advantage of these methods is that they require only simply sample preparation.

Modeling the effect of heat treatment on fatty acid composition in home-made olive oil preparations.

The aim of this study was to simulate olive oil use and to monitor changes in the profile of fatty acids in home-made preparations using olive oil, which involve repeated heat treatment cycles. The material used in the experiment consisted of extra virgin and refined olive oil samples. Fatty acid profiles of olive oil samples were monitored after each heating cycle (10 min). The outcomes showed that cycles of heat treatment cause significant (p < 0.05) differences in the fatty acid profile of olive oil. A similar trend of differences (p < 0.05) was found between fatty acid profiles in extra virgin and refined olive oils. As expected, the main differences occurred in monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs). Cross-correlation analysis also showed differences between the fatty acid profiles. The most prolific changes were observed between the control samples and the heated (at 180°C) samples of refined olive oil in PUFAs, though a heating temperature of 220°C resulted in similar decrease in MUFAs and PUFAs, in both extra virgin and refined olive oil samples. The study showed differences in fatty acid profiles that can occur during the culinary heating of olive oil. Furthermore, the study indicated that culinary heating of extra virgin olive oil produced results similar to those of the refined olive oil heating at a lower temperature below 180°C.

polyamine uptake transporter 2 (put2) and decaying seeds enhance phyA-mediated germination by overcoming PIF1 repression of germination.

Red light promotes germination after activating phytochrome phyB, which destabilizes the germination repressor PIF1. Early upon seed imbibition, canopy light, unfavorable for photosynthesis, represses germination by stabilizing PIF1 after inactivating phyB. Paradoxically, later upon imbibition, canopy light stimulates germination after activating phytochrome phyA. phyA-mediated germination is poorly understood and, intriguingly, is inefficient, compared to phyB-mediated germination, raising the question of its physiological significance. A genetic screen identified polyamine uptake transporter 2 (put2) mutants that overaccumulate polyamines, a class of antioxidant polycations implicated in numerous cellular functions, which we found promote phyA-mediated germination. In WT seeds, our data suggest that canopy light represses polyamines accumulation through PIF1 while red light promotes polyamines accumulation. We show that canopy light also downregulates PIF1 levels, through phyA; however, PIF1 reaccumulates rapidly, which limits phyA-mediated germination. High polyamines levels in decaying seeds bypass PIF1 repression of germination and stimulate phyA-mediated germination, suggesting an adaptive mechanism promoting survival when viability is compromised.

Essential Oil Profile, Phenolic Content and Antioxidant Activity of Geranium kikianum.

This work presents the first phytochemical investigation of Geranium kikianum Kit Tan & G. Vold (Geraniaceae), a species endemic to the southern Peloponnese, Greece. The essential oil from aerial parts of the plant was isolated by hydrodistillation and its chemical composition characterized by GC-MS. A total of 26 compounds were identified, constituting 98.3% of the oil composition. Oxygenated sesquiterpenes were the main group of constituents (75.4%). The major component of the oil was the sesquiterpene ketone germacrone (45.6%). Eleven alcohols represented the most diverse chemical class in the volatile oil (36.3%), and phytol was the most abundant acyclic diterpene alcohol (11.4%). The volatile compounds and residual water remaining after hydrodistillation were screened for their radical-scavenging activity by the DPPH method. IC50 values ranged from 0.2±0.03 mg/mL for the undiluted decoction to 69.7±0.5 mg/mL for the essential oil. The significant antioxidant activity of the residual water, comparable with that of the widespread synthetic antioxidant BHT. (0.2±0.01 mg/mL), and almost tenfold higher than thymol (1.90 t 0.04 mg/mL), correlates with a high content of total phenolic compounds (100.2±1.7 mg GAE/g), and flavonoids (11.9±1.2 mg GAE/g).

Variation in Phenolic Composition of Knautia arvensis in Correlation with Geographic Area and Plant Organ.

Knautia arvensis (family Dipsacaceae) is usually found in grasslands of Europe, but can also be found in some parts of Africa and Asia, usually in dry meadows, pastures, dry hills, and open woods. The chemical composition of this species is relatively unknown. The aim of this study was to give a phenolic profile of this plant, and to show how its phenolic composition varies depending upon plant organ and geographic origin. The chemical analysis included quantification of free phenolics soluble in methanol, esters and glycosides, and phenolics that are insoluble in methanol. Fourteen different phenolic acids and eight flavonoids were quantified in total. According to this study, the chemical composition of individual plant parts can differ tremendously within one - population, which does not have to be in correspondence with chemical variability between populations. As shown in this study, the variation in chemical composition between plant parts can exceed that between different populations (from different climates, altitudes, with different environmental factors), which implies that microhabitat conditions can greatly affect the composition of some plant parts, which was shown also after PCA and HCA analysis.

Volatiles of Helichrysum italicum (Roth) G. Don from Croatia.

Helichrysum italicum (Roth) G. Don is a flowering plant of the family Asteraceae. It is rich in oil that is used for different medicinal purposes and in fragrance industry. Volatile profile of four populations of H. italicum, collected from natural habitat in Dalmatia (Croatia), was analysed by capillary GC-MS. Sample from BraC Island had α-trans-bergamotene (10.2%) and ß-acoradiene (10.1%) as the majors, whereas sample collected on Biokovo Mt. was rich in neryl acetate (8.1%). ß-Acoradiene was also the main constituent of sample collected near Tijarica, whereas rosifoliol (8.5%) was the most abundant constituent in sample collected near Makarska. Presented results show the influence of environmental conditions on chemical differentiation of the volatiles of H. italicum from Croatia.