Growth enhancement of grapevine call us by catechin on auxin-free media

Proliferating Spätburgunder cells cultured in vitro were found to synthesize the monomeric and oligomeric flavanols catechin, C2, B3, B1, B2 prodelphinidin, ECG (epicatechin gallate), B2G, B2-gallate and B5. Catechin and prodelphinidin were the predominating compounds of all calli studied. Growth promotion of calli from Spatburgunder and Romulus was studied using MS media containing benzyladenine (BA) alone (control), BA plus catechin, and BA combined with two different concentrations of indole-3-acetic acid (IAA). Growth on BA alone was notably reduced. Catechin (68 µM) stimulated callus growth several-fold when combined with 0.8 µM BA; however, this effect was only observed with explants excised from internodes of vigorously growing young shoots

Flavanols in grapevine: In vitro accumulation and defence reactions in shoots

Callus of two grapevine cultivars was cultivated for 4 weeks on MS-medium, half strength, which was additionally supplemented with abscisic acid (ABA), (+)-catechin or a combination of both. (+)-Catechin did not elevate the pool size of the callus flavanols. Application of 3 % sucrose caused a significant increase of the callus flavanols, whereas the response to ABA was quite variable. Leaves and shoots of cv. Spatburgunder (Pinot noir) were examined histologically on the mode of flavanol deposition. The flavanols of the leaf mesophyll were spread evenly throughout the central vacuole whereas those of the outer shoot cortex were confined to special intravacuolar globules. The amorphous leaf flavanols were converted into globdar ones in the vicinity of fungal infections. Apparently, the central vacuole acquires special adjustment under the influence of infection stress. When paraquat was applied to the shoots, amorphous material was attached towards the cell walls. Additionally, the globular flavanols disappeared which could be reversed by addition of (+)-catechin. Thus, (+)-catechin diminished the oxidative damage caused by the oxygen radical producing herbicide. (+)-Catechin and epicatechin are the dominant flavanols of the leaves, whereas the dimeric proanthocyanidins B3 and B1 (PAs) predominate in the callus

The inheritance of the hypersensitivity resistance of European plum (Prunus domestica L.) against the Plum pox virus

In between 2003 and 2009 more than 500 seedlings have been tested for hypersensitivity resistance against the Plum pox virus (PPV), which causes Sharka disease. The seedlings had at least one hypersensitive parent genotype. They were tested for hypersensitivity resistance by double grafting onto PPV infected interstem in the green house. In crossing combinations with two hypersensitive parents the percentage of hypersensitive seedlings was highest. There is also no equal distribution of the genotypes over the individual hypersensitivity classes (HC) in all crossing combinations. The percentage of hypersensitive seedlings strongly depends on the parentage. Furthermore investigations regarding the origin of the hypersensitivity resistance of the cultivar ‘Jojo’, which is a descendant of a crossing combination from ‘Ortenauer’ × ‘Stanley’, were done. It was shown that the cultivar ‘Ortenauer’ is the donor of the hypersensitivity trait.Keywords: Plum pox virus, hypersensitivity, inheritance, Prunus domestica L., resistanc

The hypersensitivity resistance of european plum to the Plum pox virus and its potential impact on the epidemiology of the virus

Since the detection of the Plum pox virus (PPV) different strategies for Sharka containment were developed. One of the most important one is the breeding of resistant cultivars. Other than in Prunus persica and in Prunus armeniaca, in Prunus domestica a type of natural resistance was detected which seems to be able to prevent the spread of PPV both over long and short distances. Therefore, this type of Sharka resistance which is based on a hypersensitive response and has been stable for more than 20 years is suggested to have the most beneficial impact on the epidemiology of the virus compared to other mechanisms of resistance or tolerance.Keywords: Sharka containment, Prunus domestica, plum breedin

Phenolic compounds in young developing kiwifruit in relation to light exposure: Implications for fruit calcium accumulation

The interaction between light availability and the biosynthesis of phenolic compounds in fruit of kiwifruit (Actinidia deliciosa var. deliciosa, C.F. Liang et A. R. Ferguson) was investigated. Fruits were exposed either to natural light or were artificially shaded while growing on mature vines and were analysed weekly during the first 11 weeks of development. Phenols were identified and quantified by using High Performance Liquid Chromatography (HPLC). Results showed that the predominant phenolic compounds were hydroxycinnamic acids (HCAs), flavonols and the flavan 3-ol epicatechin. Calcium (Ca2+), the main mineral nutrient involved in fruit quality was also determined. Light significantly increased the accumulation of both phenols and Ca2+ into the fruit. This work expands the list of known phenolics in kiwifruit and provides a possible explanation for the seasonal pattern of Ca2+ import into the fruit. Results on light–phenol interaction being apparently beneficial for fruit Ca2+ accumulation, suggest that accurate canopy management could enhance fruit quality

Transgenic apple plants overexpressing the chalcone 3-hydroxylase gene of Cosmos sulphureus show increased levels of 3-hydroxyphloridzin and reduced susceptibility to apple scab and fire blight

Main conclusionOverexpression of chalcone-3-hydroxylase provokes increased accumulation of 3-hydroxyphloridzin inMalus. Decreased flavonoid concentrations but unchanged flavonoid class composition were observed. The increased 3-hydroxyphlorizin contents correlate well with reduced susceptibility to fire blight and scab.The involvement of dihydrochalcones in the apple defence mechanism against pathogens is discussed but unknown biosynthetic steps in their formation hamper studies on their physiological relevance. The formation of 3-hydroxyphloretin is one of the gaps in the pathway. Polyphenol oxidases and cytochrome P450 dependent enzymes could be involved. Hydroxylation of phloretin in position 3 has high similarity to the B-ring hydroxylation of flavonoids catalysed by the well-known flavonoid 3′-hydroxylase (F3′H). Using recombinant F3′H and chalcone 3-hydroxylase (CH3H) from Cosmos sulphureus we show that F3′H and CH3H accept phloretin to some extent but higher conversion rates are obtained with CH3H. To test whether CH3H catalyzes the hydroxylation of dihydrochalcones in planta and if this could be of physiological relevance, we created transgenic apple trees harbouring CH3H from C. sulphureus. The three transgenic lines obtained showed lower polyphenol concentrations but no shift between the main polyphenol classes dihydrochalcones, flavonols, hydroxycinnamic acids and flavan 3-ols. Increase of 3-hydroxyphloridzin within the dihydrochalcones and of epicatechin/catechin within soluble flavan 3-ols were observed. Decreased activity of dihydroflavonol 4-reductase and chalcone synthase/chalcone isomerase could partially explain the lower polyphenol concentrations. In comparison to the parent line, the transgenic CH3H-lines showed a lower disease susceptibility to fire blight and apple scab that correlated with the increased 3-hydroxyphlorizin contents.Austrian Sci-ence Fund (FWF

Environmentally induced changes in antioxidant phenolic compounds levels in wild plants

[EN] Different adverse environmental conditions cause oxidative stress in plants by generation of reactive oxygen species (ROS). Accordingly, a general response to abiotic stress is the activation of enzymatic and non-enzymatic antioxidant systems. Many phenolic compounds, especially flavonoids, are known antioxidants and efficient ROS scavengers in vitro, but their exact role in plant stress responses in nature is still under debate. The aim of our work is to investigate this role by correlating the degree of environmental stress with phenolic and flavonoid levels in stress-tolerant plants. Total phenolic and antioxidant flavonoid contents were determined in 19 wild species. Meteorological data and plant and soil samples were collected in three successive seasons from four Mediterranean ecosystems: salt marsh, dune, semiarid and gypsum habitats. Changes in phenolic and flavonoid levels were correlated with the environmental conditions of the plants and were found to depend on both the taxonomy and ecology of the investigated species. Despite species-specific differences, principal component analyses of the results established a positive correlation between plant phenolics and several environmental parameters, such as altitude, and those related to water stress: temperature, evapotranspiration, and soil water deficit. The correlation with salt stress was, however, very weak. The joint analysis of all the species showed the lowest phenolic and flavonoid levels in the halophytes from the salt marsh. This finding supports previous data indicating that the halophytes analysed here do not undergo oxidative stress in their natural habitat and therefore do not need to activate antioxidant systems as a defence against salinity.This work has been funded by the Spanish Ministry of Science and Innovation (Project CGL2008-00438/BOS), with contribution from the European Regional Development Fund. Thanks to Dr. Rafael Herrera for critical reading of the manuscript.Bautista, I.; Boscaiu, M.; Lidón, A.; Llinares Palacios, JV.; Lull, C.; Donat-Torres, MP.; Mayoral García-Berlanga, O.... (2016). Environmentally induced changes in antioxidant phenolic compounds levels in wild plants. Acta Physiologiae Plantarum. 38(1):1-15. https://doi.org/10.1007/s11738-015-2025-2S115381Agati G, Biricolti S, Guidi L, Ferrini F, Fini A, Tattini M (2011) The biosynthesis of flavonoids is enhanced similarly by UV radiation and root zone salinity in L. vulgare leaves. 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Relationship between the Sensory-Determined Astringency and the Flavanolic Composition of Red Wines

[EN] The relationship between the proanthocyanidin profile and the perceived astringency was assessed in 13 commercial Tempranillo red wines. The concentration and compositional information were obtained by liquid chromatography with diode array detection coupled to electrospray ionization mass spectrometry after acid-catalyzed depolymerization of wine proanthocyanidins in the presence of excess phloroglucinol. Statistical analysis of the results showed significant correlations between sensory and chemical determinations. Astringency was more affected by the subunit composition than by the total concentration or the average degree of polymerization of wine proanthocyanidins. Higher proportions of epicatechin (EC) subunits in extension positions and gallocatechin (GC) subunits in terminal positions were shown to increase astringency. On the contrary, the amount of epigallocatechin (EGC) in both extension and terminal positions was negatively correlated with the perceived astringency

Ecologically Appropriate Xenobiotics Induce Cytochrome P450s in Apis mellifera

BACKGROUND: Honey bees are exposed to phytochemicals through the nectar, pollen and propolis consumed to sustain the colony. They may also encounter mycotoxins produced by Aspergillus fungi infesting pollen in beebread. Moreover, bees are exposed to agricultural pesticides, particularly in-hive acaricides used against the parasite Varroa destructor. They cope with these and other xenobiotics primarily through enzymatic detoxificative processes, but the regulation of detoxificative enzymes in honey bees remains largely unexplored. METHODOLOGY/PRINCIPAL FINDINGS: We used several approaches to ascertain effects of dietary toxins on bee susceptibility to synthetic and natural xenobiotics, including the acaricide tau-fluvalinate, the agricultural pesticide imidacloprid, and the naturally occurring mycotoxin aflatoxin. We administered potential inducers of cytochrome P450 enzymes, the principal biochemical system for Phase 1 detoxification in insects, to investigate how detoxification is regulated. The drug phenobarbital induces P450s in many insects, yet feeding bees with phenobarbital had no effect on the toxicity of tau-fluvalinate, a pesticide known to be detoxified by bee P450s. Similarly, no P450 induction, as measured by tau-fluvalinate tolerance, occurred in bees fed xanthotoxin, salicylic acid, or indole-3-carbinol, all of which induce P450s in other insects. Only quercetin, a common pollen and honey constituent, reduced tau-fluvalinate toxicity. In microarray comparisons no change in detoxificative gene expression was detected in phenobarbital-treated bees. However, northern blot analyses of guts of bees fed extracts of honey, pollen and propolis showed elevated expression of three CYP6AS P450 genes. Diet did not influence tau-fluvalinate or imidacloprid toxicity in bioassays; however, aflatoxin toxicity was higher in bees consuming sucrose or high-fructose corn syrup than in bees consuming honey. CONCLUSIONS/SIGNIFICANCE: These results suggest that regulation of honey bee P450s is tuned to chemicals occurring naturally in the hive environment and that, in terms of toxicological capacity, a diet of sugar is not equivalent to a diet of honey

Oxidative discolouration in whole-head and cut lettuce: biochemical and environmental influences on a complex phenotype and potential breeding strategies to improve shelf-life

Lettuce discolouration is a key post-harvest trait. The major enzyme controlling oxidative discolouration has long been considered to be polyphenol oxidase (PPO) however, levels of PPO and subsequent development of discolouration symptoms have not always correlated. The predominance of a latent state of the enzyme in plant tissues combined with substrate activation and contemporaneous suicide inactivation mechanisms are considered as potential explanations for this phenomenon. Leaf tissue physical properties have been associated with subsequent discolouration and these may be influenced by variation in nutrient availability, especially excess nitrogen and head maturity at harvest. Mild calcium and irrigation stress has also been associated with a reduction in subsequent discolouration, although excess irrigation has been linked to increased discolouration potentially through leaf physical properties. These environmental factors, including high temperature and UV light intensities, often have impacts on levels of phenolic compounds linking the environmental responses to the biochemistry of the PPO pathway. Breeding strategies targeting the PALand PPOpathway biochemistry and environmental response genes are discussed as a more cost-effective method of mitigating oxidative discolouration then either modified atmosphere packaging or post-harvest treatments, although current understanding of the biochemistry means that such programs are likely to be limited in nature and it is likely that they will need to be deployed alongside other methods for the foreseeable future