Growth and production of buckwheat (Fagopyrum esculentum) treated with reduced, ambient, and enhanced UV-B radiation

Multi-omics identification of a key glycosyl hydrolase gene FtGH1 involved in rutin hydrolysis in Tartary buckwheat (Fagopyrum tataricum)

Rutin, a flavonoid rich in buckwheat, is important for human health and plant resistance to external stresses. The hydrolysis of rutin to quercetin underlies the bitter taste of Tartary buckwheat. In order to identify rutin hydrolysis genes, a 200 genotypes mini-core Tartary buckwheat germplasm resource was re-sequenced with 30-fold coverage depth. By combining the content of the intermediate metabolites of rutin metabolism with genome resequencing data, metabolite genome-wide association analyses (GWAS) eventually identified a glycosyl hydrolase gene FtGH1, which could hydrolyse rutin to quercetin. This function was validated both in Tartary buckwheat overexpression hairy roots and in vitro enzyme activity assays. Mutation of the two key active sites, which were determined by molecular docking and experimentally verified via overexpression in hairy roots and transient expression in tobacco leaves, exhibited abnormal subcellular localization, suggesting functional changes. Sequence analysis revealed that mutation of the FtGH1 promoter in accessions of two haplotypes might be necessary for enzymatic activity. Co-expression analysis and GWAS revealed that FtbHLH165 not only repressed FtGH1 expression, but also increased seed length. This work reveals a potential mechanism behind rutin metabolism, which should provide both theoretical support in the study of flavonoid metabolism and in the molecular breeding of Tartary buckwheat.

Unravelling the neglected role of ultraviolet radiation on stomata: A meta-analysis with implications for modelling ecosystem-climate interactions

Stomata play a pivotal role in regulating gas exchange between plants and the atmosphere controlling water and carbon cycles. Accordingly, we investigated the impact of ultraviolet-B radiation, a neglected environmental factor varying with ongoing global change, on stomatal morphology and function by a Comprehensive Meta-Analysis. The overall UV effect at the leaf level is to decrease stomatal conductance, stomatal aperture and stomatal size, although stomatal density was increased. The significant decline in stomatal conductance is marked (6% in trees and >10% in grasses and herbs) in short-term experiments, with more modest decreases noted in long-term UV studies. Short-term experiments in growth chambers are not representative of long-term field UV effects on stomatal conductance. Important consequences of altered stomatal function are hypothesized. In the short term, UV-mediated stomatal closure may reduce carbon uptake but also water loss through transpiration, thereby alleviating deleterious effects of drought. However, in the long term, complex changes in stomatal aperture, size, and density may reduce the carbon sequestration capacity of plants and increase vegetation and land surface temperatures, potentially exacerbating negative effects of drought and/or heatwaves. Therefore, the expected future strength of carbon sink capacity in high-UV regions is likely overestimated.

Haplotype-resolved genomes of two buckwheat crops provide insights into their contrasted rutin concentrations and reproductive systems

BACKGROUND

Two widely cultivated annual buckwheat crops, Fagopyrum esculentum and F. tataricum, differ from each other in both rutin concentration and reproductive system. However, the underlying genetic mechanisms remain poorly elucidated.

RESULTS

Here, we report the first haplotype-resolved chromosome-level genome assemblies of the two species. Two haplotype genomes of F. esculentum were assembled as 1.23 and 1.19 Gb with N50 = 9.8 and 12.4 Mb, respectively; the two haplotype genomes of F. tataricum were 453.7 and 446.2 Mb with N50 = 50 and 30 Mb, respectively. We further annotated protein-coding genes of each haplotype genome based on available gene sets and 48 newly sequenced transcriptomes. We found that more repetitive sequences, especially expansion of long terminal repeat retrotransposons (LTR-RTs), contributed to the large genome size of F. esculentum. Based on the well-annotated sequences, gene expressions, and luciferase experiments, we identified the sequence mutations of the promoter regions of two key genes that are likely to have greatly contributed to the high rutin concentration and selfing reproduction in F. tartaricum.

CONCLUSIONS

Our results highlight the importance of high-quality genomes to identify genetic mutations underlying phenotypic differences between closely related species. F. tataricum may have been experienced stronger selection than F. esculentum through choosing these two non-coding alleles for the desired cultivation traits. These findings further suggest that genetic manipulation of the non-coding promoter regions could be widely employed for breeding buckwheat and other crops.

UV-B Radiation Effects on the Alpine Plant Kobresia humilis in a Qinghai-Tibet Alpine Meadow

Enhanced UV-B radiation resulting from stratospheric ozone depletion has been documented both globally and on the Qinghai-Tibet Plateau in China. The response of Kobresia humilis, an important alpine meadow plant species, to enhanced UV-B radiation was experimentally investigated at the Haibei Alpine Meadow Ecosystem Research Station (37°29′−37°45′ N, 101°12′−101°23′ E; alt. 3200 m). K. humilis was exposed to UV-B radiation including ambient UV-B and enhanced UV-B (simulating a 14% reduction in the ozone layer) in a randomized design with three replications of each treatment. Enhanced UV-B radiation resulted in a significant increase of both leaf area and fresh weight chlorophyll and carotenoid but had no effect on UV-B absorbing pigments. Similarly, enhanced UV-B radiation did not significantly change the photosynthetic O2 elevation rate while leaf thickness, width, and length significantly increased (p < 0.01). The enhanced UV-B radiation was associated with 2−3 days earlier flowering and a larger number of flowers per spikelet. The enhanced UV-B generally resulted in larger leaves and more flowers but earlier phenology. In summary, these findings suggest that alpine species of K. humilis have adapted to the strong solar UV-B radiation intensity presented on the Qinghai-Tibet Plateau, but the interspecies differences and their influence on trophic level should be more concerning.

Molecular Shield for Protection of Buckwheat Plants from UV-B Radiation

Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn.) and common buckwheat (Fagopyrum esculentum Moench) are adapted to growing in harsh conditions of high altitudes. Ultraviolet radiation at high altitudes strongly impacts plant growth and development. Under the influence of ultraviolet radiation, protecting substances are synthesized in plants. The synthesis of UV-B defense metabolites is genetically conditioned, and their quantity depends on the intensity of the ultraviolet radiation to which the plants and plant parts are exposed. These substances include flavonoids, and especially rutin. Other substances with aromatic rings of six carbon atoms have a similar function, including fagopyrin, the metabolite specific for buckwheat. Defensive substances are formed in the leaves and flowers of common and Tartary buckwheat, up to about the same concentration in both species. In comparison, the concentration of rutin in the grain of Tartary buckwheat is much higher than in common buckwheat. Flavonoids also have other functions in plants so that they can protect them from pests and diseases. After crushing the grains, rutin is exposed to contact with the molecules of rutin-degrading enzymes. In an environment with the necessary humidity, rutin is turned into bitter quercetin under the action of rutin-degrading enzymes. This bitterness has a deterrent effect against pests. Moreover, flavonoids have important functions in human nutrition to prevent several chronic diseases, including obesity, cardiovascular diseases, gallstone formation, and hypertension.

Adaptative Responses of Common and Tartary Buckwheat to Different Altitudes

Environmental conditions at different elevations are harsher at higher elevations and impose constraints upon plants. The response of common and Tartary buckwheats to environmental conditions at elevations between 300 and 1180 m above sea level (asl) was studied. In common buckwheat, grown at the highest elevation, there was an increased investment in secondary metabolism, and decreased investment in primary metabolism, since the production of UV-absorbing compounds was enhanced while the amounts of chlorophylls and carotenoids decreased. In Tartary buckwheat, the amounts of UV-absorbing compounds, chlorophylls and carotenoids were similar in plants grown at different elevations, indicating better adaptation to conditions at higher elevations. Common and Tartary buckwheat plants from Podbeže had thicker leaves than plants from the two other locations. This could be a response to high radiation in the very sunny position in Podbeže.

Impact of Rutin and Other Phenolic Substances on the Digestibility of Buckwheat Grain Metabolites

Tartary buckwheat (Fagopyrum tataricum Gaertn.) is grown in eastern and central Asia (the Himalayan regions of China, Nepal, Bhutan and India) and in central and eastern Europe (Luxemburg, Germany, Slovenia and Bosnia and Herzegovina). It is known for its high concentration of rutin and other phenolic metabolites. Besides the grain, the other aboveground parts of Tartary buckwheat contain rutin as well. After the mixing of the milled buckwheat products with water, the flavonoid quercetin is obtained in the flour–water mixture, a result of rutin degradation by rutinosidase. Heating by hot water or steam inactivates the rutin-degrading enzymes in buckwheat flour and dough. The low buckwheat protein digestibility is due to the high content of phenolic substances. Phenolic compounds have low absorption after food intake, so, after ingestion, they remain for some time in the gastrointestinal tract. They can act in an inhibitory manner on enzymes, degrading proteins and other food constituents. In common and Tartary buckwheat, the rutin and quercetin complexation with protein and starch molecules has an impact on the in vitro digestibility and the appearance of resistant starch and slowly digestible proteins. Slowly digestible starch and proteins are important for the functional and health-promoting properties of buckwheat products.

Ultraviolet-B induced changes in physiology, phenylpropanoid pathway, and essential oil composition in two Curcuma species (C. caesia Roxb. and C. longa L.)

Ultraviolet-B is an important fraction of sunlight which influences the plant performance either positively or adversely in terms of growth, physiology, biochemistry, and major active compounds. The static nature of plants constrains them to be subjected to various adverse environmental conditions. Several studies performed with plants and UV-B with fewer reports are available on medicinal plants having rhizome. The present study focuses on transformation induced in two Curcuma spp. (C. caesia and C. longa) under the influence of elevated UV-B (eUV-B) (ambient ±9.6 kJ m^-2 d^-1) under natural field conditions to analyse the changes in physiological, biochemical and essential oil of the test plants. eUV-B significantly reduced the photosynthetic activities such as photosynthetic rate (P_s), stomatal conductance (g_s), transpiration (T_r), internal CO₂ (C_i), and photochemical efficiency (F_v/F_m) with higher reductions in C. longa as compared to C. caesia. The enzymatic activities of PAL, CHI, and CAD showed higher stimulation in C. caesia whereas C. longa showed increment only in CAD. The essential oil content was increased by 16% and 9% in C. caesia and C. longa, respectively. C. caesia showed increased monoterpenes than sesquiterpenes, whereas almost equal increase of both the terpenoid found in C. longa. C. caesia showed induction of aromatic compounds (epiglobulol, germacrene, 4-terpineol), whereas anticancerous compounds; aphla-terpinolene (61%), beta-caryophyllene (60%), and beta-sesquiphellandrene (32%) were increased in C. longa. C. caesia acted well in terms of both physiology and major active compound (1, 8-cineole), but overall most of the compounds increased in C. longa under eUV-B.

Breeding Buckwheat for Increased Levels of Rutin, Quercetin and Other Bioactive Compounds with Potential Antiviral Effects

Common buckwheat (Fagopyrum esculentum Moench) and Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn.) are sources of many bioactive compounds, such as rutin, quercetin, emodin, fagopyrin and other (poly)phenolics. In damaged or milled grain under wet conditions, most of the rutin in common and Tartary buckwheat is degraded to quercetin by rutin-degrading enzymes (e.g., rutinosidase). From Tartary buckwheat varieties with low rutinosidase activity it is possible to prepare foods with high levels of rutin, with the preserved initial levels in the grain. The quercetin from rutin degradation in Tartary buckwheat grain is responsible in part for inhibition of α-glucosidase in the intestine, which helps to maintain normal glucose levels in the blood. Rutin and emodin have the potential for antiviral effects. Grain embryos are rich in rutin, so breeding buckwheat with the aim of producing larger embryos may be a promising strategy to increase the levels of rutin in common and Tartary buckwheat grain, and hence to improve its nutritional value.

Water Shortage Strongly Alters Formation of Calcium Oxalate Druse Crystals and Leaf Traits in Fagopyrum esculentum

Common buckwheat (Fagopyrum esculentum Moench) is a robust plant with high resistance to different environmental constraints. It contains high levels of calcium oxalate (CaOx) druse crystals, although their role remains obscure. The objective was to examine the effects of water shortage on plant biomass partition and leaf traits and formation of CaOx druse crystals in common buckwheat. Buckwheat plants were exposed to favorable and reduced water availability for 28 days. The element composition and morphological, biochemical, physiological and optical traits of the leaves, and the plant biomass were investigated under these conditions. Measurements of photochemical efficiency of photosystem II showed undisturbed functioning for buckwheat exposed to water shortage, apparently due to partially closed stomata and more efficient water regulation. Strong relationships were seen between water-related parameters and Ca, Mn and S content, and size and density of CaOx druse crystals. Redundancy analysis revealed the importance of the size of CaOx druse crystals to explain reflection in the UV range. Water shortage resulted in shorter plants with the same leaf mass (i.e., increased mass:height ratio), which, together with denser leaf tissue and higher content of photosynthetic pigments and protective substances, provides an advantage under extreme weather conditions.

Molecular Cloning and Expression of a Cryptochrome Gene CiCRY-DASH1 from the Antarctic microalga Chlamydomonas sp. ICE-L

Cryptochromes (CRYs) are flavin-binding proteins that sense blue and near-ultraviolet light and participate in the photoreactions of organisms and the regulation of biological clocks. In this study, the complete open reading frame (ORF) of CiCRY-DASH1 (GenBank ID MK392361), encoding one kind of cryptochrome, was cloned from the Antarctic microalga Chlamydomonas sp. ICE-L. The quantitative real-time PCR study showed that the CiCRY-DASH1 had the highest expression at 5 °C and salinity of 32‰. The CiCRY-DASH1 was positively regulated by blue, yellow, or red light. Moreover, the CiCRY-DASH1 can positively respond to extreme polar day and night treatment and exhibit a certain circadian rhythm, which indicated that CiCRY-DASH1 participated in the circadian clock and its expression was regulated by circadian rhythms. And the CiCRY-DASH1 was more noticeably affected by ultraviolet-B radiation than ultraviolet-A radiation, indicating ultraviolet-B light does obvious damage to Antarctic microalgae.

Elevated air humidity increases UV mediated leaf and DNA damage in pea (Pisum sativum) due to reduced flavonoid content and antioxidant power

Growth in high relative air humidity (RH, >85%) affects plant morphology and causes diminished response to stomatal closing signals. Many greenhouses are prone to high RH conditions, which may negatively affect production and post-harvest quality. UV radiation induces stomatal closure in several species, and facilitates disease control. We hypothesised that UV exposure may trigger stomatal closure in pea plants (Pisum sativum) grown in high RH, thereby restoring stomatal function. The effects of UV exposure were tested on plants grown in moderate (60%) or high (90%) RH. UV exposure occurred at night, according to a disease control protocol. Lower stomatal conductance rates were found in UV-exposed plants, though UV exposure did not improve the rate of response to closing stimuli or desiccation tolerance. UV-exposed plants showed leaf curling, chlorosis, necrosis, and DNA damage measured by the presence of cyclobutane pyrimidine dimers (CPD), all of which were significantly greater in high RH plants. These plants also had lower total flavonoid content than moderate RH plants, and UV-exposed plants had less than controls. Plants exposed to UV had a higher content of cuticular layer uronic compounds than control plants. However, high RH plants had a higher relative amount of cuticular waxes, but decreased proteins and uronic compounds. Plants grown in high RH had reduced foliar antioxidant power compared to moderate RH. These results indicate that high RH plants were more susceptible to UV-induced damage than moderate RH plants due to reduced flavonoid content and oxidative stress defence.

Genome-wide Analysis of the WRKY Gene Family and its Response to Abiotic Stress in Buckwheat (Fagopyrum Tataricum)

The WRKY gene family is an ancient plant transcription factor (TF) family with a vital role in plant growth and development, especially in response to biotic and abiotic stresses. Although many researchers have studied WRKY TFs in numerous plant species, little is known of them in Tartary buckwheat (Fagopyrum tataricum). Based on the recently reported genome sequence of Tartary buckwheat, we identified 78 FtWRKY proteins that could be classified into three major groups. All 77 WRKY genes were distributed unevenly across all eight chromosomes. Exon-intron analysis and motif composition prediction revealed the complexity and diversity of FtWRKYs, indicating that WRKY TFs may be of significance in plant growth regulation and stress response. Two separate pairs of tandem duplication genes were found, but no segmental duplications were identified. Overall, most orthologous gene-pairs between Tartary and common buckwheat evolved under strong purifying selection. qRT-PCR was used to analyze differences in expression among four FtWRKYs (FtWRKY6, 74, 31, and 7) under salt, drought, cold, and heat treatments. The results revealed that all four proteins are related to abiotic stress responses, although they exhibited various expression patterns. In particular, the relative expression levels of FtWRKY6, 74, and 31 were significantly upregulated under salt stress, while the highest expression of FtWRKY7 was observed from heat treatment. This study provides comprehensive insights into the WRKY gene family in Tartary buckwheat, and can support the screening of additional candidate genes for further functional characterization of WRKYs under various stresses.

Distinct physiological and metabolic reprogramming by highbush blueberry (Vaccinium corymbosum) cultivars revealed during long-term UV-B radiation

Despite the Montreal protocol and the eventual recovery of the ozone layer over Antarctica, there are still concerns about increased levels of ultraviolet-B (UV-B) radiation in the Southern Hemisphere. UV-B induces physiological, biochemical and morphological stress responses in plants, which are species-specific and different even for closely related cultivars. In woody plant species, understanding of long-term mechanisms to cope with UV-B-induced stress is limited. Therefore, a greenhouse UV-B daily course simulation was performed for 21 days with two blueberry cultivars (Legacy and Bluegold) under UV-B_BE irradiance doses of 0, 0.07 and 0.19 W m^-2 . Morphological changes, photosynthetic performance, antioxidants, lipid peroxidation and metabolic features were evaluated. We found that both cultivars behaved differently under UV-B exposure, with Legacy being a UV-B-resistant cultivar. Interestingly, Legacy used a combined strategy: initially, in the first week of exposure its photoprotective compounds increased, coping with the intake of UV-B radiation (avoidance strategy), and then, increasing its antioxidant capacity. These strategies proved to be UV-B radiation dose dependent. The avoidance strategy is triggered early under high UV-B radiation in Legacy. Moreover, the rapid metabolic reprogramming capacity of this cultivar, in contrast to Bluegold, seems to be the most relevant contribution to its UV-B stress-coping strategy.

Impact of UV-A radiation on the performance of aphids and whiteflies and on the leaf chemistry of their host plants

Ultraviolet (UV) radiation directly regulates a multitude of herbivore life processes, in addition to indirectly affecting insect success via changes in plant chemistry and morphogenesis. Here we looked at plant and insect (aphid and whitefly) exposure to supplemental UV-A radiation in the glasshouse environment and investigated effects on insect population growth. Glasshouse grown peppers and eggplants were grown from seed inside cages covered by novel plastic filters, one transparent and the other opaque to UV-A radiation. At a 10-true leaf stage for peppers (53 days) and 4-true leaf stage for eggplants (34 days), plants were harvested for chemical analysis and infested by aphids and whiteflies, respectively. Clip-cages were used to introduce and monitor the insect fitness and populations of the pests studied. Insect pre-reproductive period, fecundity, fertility and intrinsic rate of natural increase were assessed. Crop growth was monitored weekly for 7 and 12 weeks throughout the crop cycle of peppers and eggplants, respectively. At the end of the insect fitness experiment, plants were harvested (68 days and 18-true leaf stage for peppers, and 104 days and 12-true leaf stage for eggplants) and leaves analysed for secondary metabolites, soluble carbohydrates, amino acids, total proteins and photosynthetic pigments. Our results demonstrate for the first time, that UV-A modulates plant chemistry with implications for insect pests. Both plant species responded directly to UV-A by producing shorter stems but this effect was only significant in pepper whilst UV-A did not affect the leaf area of either species. Importantly, in pepper, the UV-A treated plants contained higher contents of secondary metabolites, leaf soluble carbohydrates, free amino acids and total content of protein. Such changes in tissue chemistry may have indirectly promoted aphid performance. For eggplants, chlorophylls a and b, and carotenoid levels decreased with supplemental UV-A over the entire crop cycle but UV-A exposure did not affect leaf secondary metabolites. However, exposure to supplemental UV-A had a detrimental effect on whitefly development, fecundity and fertility presumably not mediated by plant cues as compounds implied in pest nutrition - proteins and sugars - were unaltered.

Metabolomic analysis and phenylpropanoid biosynthesis in hairy root culture of tartary buckwheat cultivars

Buckwheat, Fagopyrum tataricum Gaertn., is an important medicinal plant, which contains several phenolic compounds, including one of the highest content of rutin, a phenolic compound with anti-inflammatory properties. An experiment was conducted to investigate the level of expression of various genes in the phenylpropanoid biosynthetic pathway to analyze in vitro production of anthocyanin and phenolic compounds from hairy root cultures derived from 2 cultivars of tartary buckwheat (Hokkai T8 and T10). A total of 47 metabolites were identified by gas chromatography–time-of-flight mass spectrometry (GC-TOFMS) and subjected to principal component analysis (PCA) in order to fully distinguish between Hokkai T8 and T10 hairy roots. The expression levels of phenylpropanoid biosynthetic pathway genes, through qRT-PCR, showed higher expression for almost all the genes in T10 than T8 hairy root except for FtF3’H-2 and FtFLS-2. Rutin, quercetin, gallic acid, caffeic acid, ferulic acid, 4-hydroxybenzoic acid, and 2 anthocyanin compounds were identified in Hokkai T8 and T10 hairy roots. The concentration of rutin and anthocyanin in Hokkai T10 hairy roots of tartary buckwheat was several-fold higher compared with that obtained from Hokkai T8 hairy root. This study provides useful information on the molecular and physiological dynamic processes that are correlated with phenylpropanoid biosynthetic gene expression and phenolic compound content in F. tataricum species.

UV-B radiation affects flavonoids and fungal colonisation in Fagopyrum esculentum and F. tataricum

In the present study, we have evaluated the effects of increased UV-B radiation that simulates 17% ozone depletion, on fungal colonisation and concentrations of rutin, catechin and quercetin in common buckwheat (Fagopyrum esculentum) and tartary buckwheat (Fagopyrum tataricum). Induced root growth and reduced shoot:root ratios were seen in both of these buckwheat species after enhanced UV-B radiation. There was specific induction of shoot quercetin concentrations in UV-B-treated common buckwheat, whereas there were no specific responses for flavonoid metabolism in tartary buckwheat. Root colonisation with arbuscular mycorrhizal fungi significantly reduced catechin concentrations in common buckwheat roots, and induced rutin concentrations in tartary buckwheat, but did not affect shoot concentrations of the measured phenolics. Specific UV-B-related reductions in the density of microsclerotia were observed in tartary buckwheat, indicating a mechanism that potentially affects fungus-plant interactions. The data support the hypothesis that responses to enhanced UV-B radiation can be influenced by the plant pre-adaptation properties and related changes in flavonoid metabolism.

Expression of flavonoid biosynthesis genes vis-à-vis rutin content variation in different growth stages of Fagopyrum species

Buckwheat is one of the field crops with the highest concentration of rutin, an important flavonoid of medicinal value. Two species of buckwheat, Fagopyrum esculentum and Fagopyrum tataricum, are the major sources of rutin. Seeds of latter contain 40-50× higher rutin compared to the former. The physiological and molecular bases of rutin content variation between Fagopyrum species are not known. The current study investigated the differences in rutin content in seeds and in other tissues and growth stages of two Fagopyrum species, and also correlated those differences with the expression of flavonoid pathway genes. The analysis of rutin content dynamics at different growth stages, S1-S9 (from seed germination to mature seed formation) of Fagopyrum species revealed that rutin content was higher during seedling stages of F. tataricum (3.5 to 4.6-fold) compared to F. esculentum and then increased exponentially from stages S3 to S6 (different leaf maturing stages and inflorescence) of F. esculentum, whereas it fluctuated in F. tataricum. The rutin content was highest in the inflorescence stage (S6) of both species, with a relatively higher biosynthesis and accumulation during post-flowering stages of F. tataricum compared to F. esculentum. The expression of flavonoid pathway genes, through qRT-PCR, in different growth stages vis-à-vis rutin content variation showed differential expression for four genes, PAL, CHS, CHI and FLS with the amounts of transcripts relatively higher in F. tataricum compared to F. esculentum, thereby, correlating these genes with the biosynthesis and accumulation of rutin. The expression of PAL was highest, 7.69 and 8.96-fold in Stages 2 (seedling stage) and 9 (fully developed seeds) of F. tataricum compared to F. esculentum, respectively. The expression of the CHS gene correlated with the rutin content because it was highest in the flowers (S6) and fully developed seeds (S9) of both Fagopyrum species, with relatively higher transcript amounts (2.13 and 3.19-fold, respectively) in F. tataricum (IC-329457) compared to F. esculentum (IC-540858). This study provides useful information on molecular and physiological dynamics of rutin biosynthesis and accumulation in Fagopyrum species and the correlation of expression of flavonoid biosynthesis genes with the rutin content can be useful in planning for genetic improvement.

Comparison of various easy-to-use procedures for extraction of phenols from apricot fruits

Phenols are broadly distributed in the plant kingdom and are the most abundant secondary metabolites of plants. Plant polyphenols have drawn increasing attention due to their potential antioxidant properties and their marked effects in the prevention of various oxidative stress associated diseases such as cancer. The objective of this study was to investigate a suitable method for determination of protocatechuic acid, 4-aminobenzoic acid, chlorogenic acid, caffeic acid, vanillin, p-coumaric acid, rutin, ferulic acid, quercetin, resveratrol and quercitrin from apricot samples. A high-performance liquid chromatograph with electrochemical and UV detectors was used. The method was optimized in respect to both the separation selectivity of individual phenolic compounds and the maximum sensitivity with the electrochemical detection. The lowest limits of detection (3 S/N) using UV detection were estimated for ferulic acid (3 µM), quercitrin (4 µM) and quercetin (4 µM). Using electrochemical detection values of 27 nM, 40 nM and 37 nM were achieved for ferulic acid, quercitrin and quercetin, respectively. It follows from the acquired results that the coulometric detection under a universal potential of 600 mV is more suitable and sensitive for polyphenols determination than UV detection at a universal wavelength of 260 nm. Subsequently, we tested the influence of solvent composition, vortexing and sonication on separation efficiency. Our results showed that a combination of water, acetone and methanol in 20:20:60 ratio was the most effective for p-aminobenzoic acid, chlorgenic acid, caffeic acid, protocatechuic acid, ferulic acid, rutin, resveratrol and quercetin, in comparison with other solvents. On the other hand, vortexing at 4 °C produced the highest yield. Moreover, we tested the contents of individual polyphenols in the apricot cultivars Mamaria, Mold and LE-1075. The major phenolic compounds were chlorgenic acid and rutin. Chlorgenic acid was found in amounts of 2,302 mg/100 g in cultivar LE-1075, 546 mg/100 g in cultivar Mamaria and 129 mg/100 g in cultivar Mold. Generally, the cultivar LE-1075 produced the highest polyphenol content values, contrary to Mold, which compared to cultivar LE-1075 was quite poor from the point of view of the phenolics content.

Differential expression of anthocyanin biosynthetic genes and anthocyanin accumulation in tartary buckwheat cultivars 'Hokkai t8' and 'Hokkai t10'

Six genes involved in anthocyanin biosynthesis in tartary buckwheat have been cloned, namely, FtC4H, Ft4CL, FtCHI, FtF3H, FtF3'H, and FtANS, which encode cinnamate 4-hydroxylase (C4H), 4-coumarate:CoA ligase (4CL), chalcone isomerase (CHI), flavones 3-hydroxylase (F3H), flavonoid 3'-hydroxylase (F3'H), and anthocyanidin synthase (ANS), respectively. Then, these cDNAs were used, along with previously isolated clones for phenylalanine ammonia-lyase (PAL) and chalcone synthase (CHS), to compare gene expression in different organs, flowering stages, and maturing seeds of tartary buckwheat cultivars 'Hokkai T8' and 'Hokkai T10'. Quantitative real-time polymerase chain reaction analysis showed that these anthocyanin biosynthetic genes were most highly expressed in the stems and roots of Hokkai T10. The FtANS gene was more highly expressed than other genes during flowering and maturing seeds. In addition, the anthocyanin concentration was higher in 'Hokkai T10' than in 'Hokkai T8'; however, naringenin chalcone, a flavonoid, was absent from 'Hokkai T10' seedlings based on fluorescence microscopy.

Effect of ultraviolet radiation on chlorophyll, carotenoid, protein and proline contents of some annual desert plants

Investigation was carried out to find whether enhanced ultraviolet radiation influences the Malva parviflora L., Plantago major L., Rumex vesicarius L. and Sismbrium erysimoids Desf. of some annual desert plants. The seeds were grown in plastic pots equally filled with a pre-sieved normal sandy soil for 1 month. The planted pots from each species were randomly divided into equal groups (three groups). Plants of the first group exposed to white-light tubes (400-700 nm) 60 w and UV (365 nm) 8 w tubes. The second group was exposed to white-light tubes (400-700 nm) 60 w and UV (302 nm) 8 w tubes. The third group was exposed to white-light tubes (400-700 nm) 60 w and UV (254 nm) 8 w tubes, respectively, for six days. The results indicated that the chlorophyll contents were affected by enhanced UV radiation. The chlorophyll a, b, and total contents were decreased compared with the control values and reduced with the enhanced UV radiation, but the carotenoid was increased compared with the control and also reduced with the enhanced UV radiation. So, the contents of chlorophylls varied considerably. M. parviflora showed the highest constitutive levels of accumulated chlorophyll a, b, and total chlorophyll (0.463, 0.307 and 0.774 mg g(-1) f w) among the investigated plant species. P. major showed the lowest constitutive levels of the chloroplast pigments, 0.0036, 0.0038 and 0.0075 mg g(-1) f w for chlorophyll a, b, and total chlorophyll at UV-365 nm, respectively. The protein content was decreased significantly in both root and shoot systems compared with the control values but, it was increased with increasing wave lengths of UV-radiation of all tested plants. R. vesicarius showed the highest protein contents among the investigated plants; its content was 3.8 mg g(-1) f w at UV-365 nm in shoot system. On the other hand, decreasing ultraviolet wave length induced a highly significant increase in the level of proline in both root and shoot of all tested plants. From the results obtained, it is suggested that proline can protect cells against damage induced by ultraviolet radiation. Statistically, the variations of the studied metabolic activities were significant due to UV radiation treatment in shoot and root system of all investigated plant species.

Degradation of rutin and polyphenols during the preparation of tartary buckwheat bread

The impact of bread making and baking procedure on rutin, quercetin and polyphenol concentration and antioxidant activity of tartary buckwheat (Fagopyrum tataricum) bread and breads made of mixtures of tartary buckwheat and wheat flour was studied. A decrease in polyphenol concentration through baking was observed in all samples. The high DPPH (2,2-diphenyl-1-picrylhydrazyl) scavenging capacity in mixed breads (32-56%) and in tartary buckwheat bread (85-90%) decreased slightly through the bread making process, while an increase of antioxidant activity in bread made of 100% wheat flour during bread making was observed. With the addition of water to mixtures containing tartary buckwheat during the preparation of the dough, rutin concentration decreased, while quercetin concentration increased. The rutin concentration continued to decrease during the bread baking process, while the concentration of quercetin remained stable. After baking, rutin (0.47 mg/g) was present only in bread made of 100% tartary buckwheat flour along with quercetin (4.83 mg/g).

Selenium and its species distribution in above-ground plant parts of selenium enriched buckwheat (Fagopyrum esculentum Moench)

Common buckwheat (Fagopyrum esculentum Moench) was foliarly sprayed with a water solution containing 10 mg Se(VI) L(-1) at the beginning of flowering. The total Se content in plant parts in the untreated group was low, whereas in the Se-sprayed group it was approximately 50- to 500-fold higher, depending on the plant part (708-4231 ng Se g(-1) DM(-1) (DM: dry matter)). We observed a similar distribution of Se in plant parts in both control and treated groups, with the highest difference in Se content being in ripe seeds. Water-soluble Se compounds were extracted by enzymatic hydrolysis with protease XIV, resulting in above 63% of soluble Se from seeds, approximately 14% from stems, leaves and inflorescences and less than 1% from husks. Se-species were determined in enzymatic extracts using HPLC-UV-HG-AFS (HPLC-hydride generation-atomic fluorescence spectrometry with UV treatment). The main Se species found in seeds was SeMet ( approximately 60% according to total Se content), while in stems, leaves and inflorescences the only form of soluble Se present was Se(VI) (up to 10% of total Se). In husks no Se-species were detected. We observed an instability of Se(IV) in seed extracts as a possible consequence of binding to the matrix components. Therefore, special care concerning sample extraction and the storage time of the extracts should be taken.

Morphological and physiological responses of two varieties of a highland species (Chenopodium quinoa Willd.) growing under near-ambient and strongly reduced solar UV-B in a lowland location

Morphological and physiological responses of seedlings to different solar UV-B irradiances were evaluated in two varieties of quinoa (Chenopodium quinoa Willd.), a crop species from Andean region of South America. Cristalina and Chucapaca varieties were grown at 1965m a.s.l in a glasshouse under natural light conditions for 18 days, and then transferred to outdoors under near-ambient (+UV-B) and strongly reduced (-UV-B) solar UV-B radiation. Exposition to -UV-B increased cotyledon area and seedling height in Cristalina variety whereas leaf number decreased compared to +UV-B. By contrast Chucapaca variety was not affected by UV-B treatments. Seedling fresh weight (FW), root length and leaf thickness did not show significant differences between +UV-B and -UV-B treatments. Mesophyll tissue was slightly affected by solar UV-B reduction. Chlorophyll content was differentially affected by UV-B treatments. Under +UV-B the highest value was observed in Cristalina variety, while in Chucapaca it was observed under -UV-B treatment. Chlorophyll content was slightly higher in leaves than in cotyledons, but there was no difference in the distribution pattern. Chlorophyll a/b ratio and carotenoid content did not show significant differences between UV-B treatments. Leaf UVB-absorbing compounds showed significant differences between UV-B treatments in Chucapaca only, while there were no significant differences in Cristalina variety. UVB-absorbing compounds of cotyledons did not show significant differences between +UV-B and -UV-B treatments. Sucrose, glucose and fructose showed different distribution patterns in cotyledons and leaves of the two varieties under near-ambient and strongly reduced UV-B. Results demonstrated that varieties of quinoa exhibit different morphological and physiological responses to changes in solar UV-B irradiance, but these responses cannot be used to predict the sensitivity to solar UV-B during a short-term exposition. Also, this study can be useful to learn about the plasticity of metabolic pathways involved in plant's tolerance to solar UV-B radiation.

Mycorrhizal status and diversity of fungal endophytes in roots of common buckwheat (Fagopyrum esculentum) and tartary buckwheat (F. tataricum)

To determine the mycorrhizal status and to identify the fungi colonising the roots of the plants, common buckwheat (Fagopyrum esculentum) and tartary buckwheat (F. tataricum) were inoculated with an indigenous fungal mixture from a buckwheat field. Root colonisation was characterised by the hyphae and distinct microsclerotia of dark septate endophytes, with occasional arbuscules and vesicles of arbuscular mycorrhizal fungi. Sequences of arbuscular mycorrhizal fungi colonising tartary buckwheat clustered close to the Glomus species group A. Sequences with similarity to the Ceratobasidium/Rhizoctonia complex, a putative dark septate endophyte fungus, were amplified from the roots of both common and tartary buckwheat. To the best of our knowledge, this is the first report of arbuscular mycorrhizal colonisation in tartary buckwheat and the first molecular characterisation of these fungi that can colonise both of these economically important plant species.

Antioxidative enzymes in the response of buckwheat (Fagopyrum esculentum moench) to ultraviolet B radiation

The behavior of the enzymatic antioxidant defense system was studied in buckwheat leaves and seedlings subjected to short-term enhanced UV-B radiation. The effects of UV-B action were monitored immediately after irradiation as well as after recovery. The applied dose induced an increase in lipid peroxidation and total flavonoid content, a decrease in chlorophyll content, and a change in enzymatic digestibility of extracted DNA. The activity of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase, and soluble peroxidase, as well as the isoelectric focusing (IEF) pattern of peroxidase isoforms, was analyzed. In treated as well as recovered seedlings, soluble and ascorbate peroxidase activities were increased. The activity of SOD was not altered, whereas CAT activity was decreased. In contrast to seedlings, only CAT activity was increased in treated and recovered leaves.

A comparison of UV-B induced stress responses in three barley cultivars

In order to investigate the role of potential genotypic differences in three economically important barley cultivars, experiments were carried out to determine the influence of supplemental ultraviolet-B (UV-B, 280-320 nm) radiation on reactive oxygen species (ROS), antioxidant activity and photosynthesis. Greenhouse-grown barley (Hordeum vulgare L.) cultivars 'Cork', 'Prestige' and 'Golden Promise' showed different responses to supplemental 280-320 nm (UV-B) representing 100, 138 and 238% levels of ambient biologically active UV-B radiation, respectively. Among the three cultivars studied, cv. Golden Promise was the most tolerant to UV-B, cv. Prestige was slightly more sensitive than cv. Cork. A comparison with the other two cultivars showed that under supplemental UV-B, Golden Promise leaves (i) retained a higher quantum yield of photosynthesis under photosynthetically active radiation (PAR, 400-700 nm) corresponding to growth conditions; (ii) had the smallest decrease in both electron transport rate and non-photochemical quenching under high PAR; (iii) contained less oxidized ascorbate [measured as dehydroascorbate or electron paramagnetic resonance (EPR) detectable monodehydroascorbate radicals] than either Cork or Prestige. Under the highest UV-B level applied, Golden Promise leaves maintained the same activity of both monodehydroascorbate-reductase (MDAR) and ascorbate-peroxidase (APX) enzymes, as untreated controls, while MDAR markedly decreased in the other two cultivars and APX slightly increased in cv. Prestige. These features, together with the observation of directly EPR-trappable free radicals and the light-independent accumulation of monodehydroascorbate radicals in Cork and Prestige but not in Golden Promise leaves under high UV-B suggest that Golden Promise plants suffered less oxidative stress than the two other cultivars.

Influence of UV-B exclusion and selenium treatment on photochemical efficiency of photosystem II, yield and respiratory potential in pumpkins (Cucurbita pepo L.)

The influence of ambient and filtered solar ultraviolet-B (UV)-B radiation and of selenium treatment was determined on photochemical efficiency, respiratory potential measured by electron transport system (ETS) activity, and yield in pumpkins, Cucurbita pepo L. Yield and ETS activity were higher when solar UV-B was filtered out. The results suggested that the decreased yield was related to the UV-B impaired flow of electrons in the respiratory chain. Selenium increased yield under ambient radiation conditions. However, no significant effect of excluding UV-B radiation or of treatment with selenium was observed on the photochemical efficiency of photosystem II (PSII).

Tartary buckwheat (Fagopyrum tataricum Gaertn.) as a source of dietary rutin and quercitrin

Two samples of tartary buckwheat (Fagopyrum tataricum Gaertn.) from China and one from Luxembourg were studied by high-performance liquid chromatography (HPLC) to reveal the possibilities of growing tartary buckwheat herb as a possible source of rutin, quercetin, and quercitrin. The content of rutin was determined as up to 3% dry weight (DW) in tartary buckwheat herb. Quercitrin values were in the range of 0.01-0.05% DW. Only traces of quercetin were detected in just some of the samples. Tartary buckwheat seeds contained more rutin (about 0.8-1.7% DW) than common buckwheat seeds (0.01% DW). Rutin and quercetin content in seeds depends on variety and growing conditions. Tartary buckwheat seeds contained traces of quercitrin and quercetin, which were not found in common buckwheat seeds.

The role of UV-B radiation in aquatic and terrestrial ecosystems--an experimental and functional analysis of the evolution of UV-absorbing compounds

We analysed and compared the functioning of UV-B screening pigments in plants from marine, fresh water and terrestrial ecosystems, along the evolutionary line of cyanobacteria, unicellular algae, primitive multicellular algae, charophycean algae, lichens, mosses and higher plants, including amphibious macrophytes. Lichens were also included in the study. We were interested in the following key aspects: (a) does the water column function effectively as an 'external UV-B filter'?; (b) do aquatic plants need less 'internal UV-B screening' than terrestrial plants?; (c) what role does UV screening play in protecting the various plant groups from UV-B damage, such as the formation of thymine dimers?; and (d) since early land 'plants' (such as the predecessors of present-day cyanobacteria, lichens and mosses) experienced higher UV-B fluxes than higher plants, which evolved later, are primitive aquatic and land organisms (cyanobacteria, algae, lichens, mosses) better adapted to present-day levels of UV-B than higher plants? Furthermore, polychromatic action spectra for the induction of UV screening pigments of aquatic organisms have been determined. This is relevant for translating 'physical' radiation measurements of solar UV-B into 'biological' and 'ecological' effects. From the action spectra, radiation amplification factors (RAFs) have been calculated. These action spectra allow us to determine any mitigating or antagonistic effects in the ecosystems and therefore qualify the damage prediction for the ecosystems under study. We summarize and discuss the main results based on three years of research of four European research groups. The central theme of the work was the investigation of the effectiveness of the various screening compounds from the different species studied in order to gain some perspective of the evolutionary adaptations from lower to higher plant forms. The induction of mycosporine-like amino acids (MAAs) was studied in the marine dinoflagellate Gyrodinium dorsum, the green algal species Prasiola stipitata and in the cyanobacterium Anabaena sp. While visible (400-700 nm) and long wavelength UV-A (315-400 nm) showed only a slight effect, MAAs were effectively induced by UV-B (280-315 nm). The growth of the lower land organisms studied, i.e. the lichens Cladina portentosa, Cladina foliacaea and Cladonia arbuscula, and the club moss Lycopodiumannotinum, was not significantly reduced when grown under elevated UV-B radiation (simulating 15% ozone depletion). The growth in length of the moss Tortula ruralis was reduced under elevated UV-B. Of the aquatic plants investigated the charophytes Chara aspera showed decreased longitudinal growth under elevated UV-B. In the 'aquatic higher plants' studied, Ceratophyllum demersum, Batrachium trichophyllum and Potamogeton alpinus, there was no such depressed growth with enhanced UV-B. In Chara aspera, neither MAAs nor flavonoids could be detected. Of the terrestrial higher plants studied, Fagopyrum esculentum, Deschampsia antarctica, Vicia faba, Calamagrostis epigejos and Carex arenaria, the growth of the first species was depressed with enhanced UV-B, in the second species length growth was decreased, but the shoot number was increased, and in the latter two species of a dune grassland there was no reduced growth with enhanced UV-B. In the dune grassland species studied outdoors, at least five different flavonoids appeared in shoot tissue. Some of the flavonoids in the monocot species, which were identified and quantified with HPLC, included orientin, luteolin, tricin and apigenin. A greenhouse study with Vicia faba showed that two flavonoids (aglycones) respond particularly to enhanced UV-B. Of these, quercetin is UV-B inducible and mainly located in epidermal cells, while kaempferol occurs constitutively. In addition to its UV-screening function, quercetin may also act as an antioxidant. Polychromatic action spectra were determined for induction of the UV-absorbing pigments in three photosynthetic organisms, representing very different taxonomic groups and different habitats. In ultraviolet photobiology, action spectra mainly serve two purposes: (1) identification of the molecular species involved in light absorption; and (2) calculation of radiation amplification factors for assessing the effect of ozone depletion. Radiation amplification factors (RAFs) were calculated from the action spectra. In a somewhat simplified way, RAF can be defined as the percent increase of radiation damage for a 1% depletion of the ozone layer. Central European summer conditions were used in the calculations, but it has been shown that RAF values are not critically dependent on latitude or season. If only the ultraviolet spectral region is considered, the RAF values obtained are 0.7 for the green alga Prasiola stipitata, 0.4 for the dinoflagellate Gyrodinium dorsum, and 1.0 for the cyanobacterium Anabaena sp. In the case of P. stipitata, however, the effect of visible light (PAR, photosynthetically active radiation, 400-700 nm) is sufficient to lower the RAF to about 0.4, while the PAR effect for G. dorsum is negligible. RAFs for some damage processes, such as for DNA damage (RAF=2.1 if protective effects or photorepair are not considered [1]), are higher than those above. Our interpretation of this is that if the ozone layer is depleted, increased damaging radiation could overrule increased synthesis of protective pigments. In addition to investigating the functional effectiveness of the different screening compounds, direct UV effects on a number of key processes were also studied in order to gain further insight into the ability of the organisms to withstand enhanced UV-B radiation. To this end, the temperature-dependent repair of cyclobutane dimers (CPD) and (6-4) photoproducts induced by enhanced UV-B was studied in Nicotiana tabacum, and the UV-B induction of CPD was studied in the lichen Cladonia arbuscula. Also, photosynthesis and motility were monitored and the response related to the potential function of the screening compounds of the specific organism.