Salicylic acid and salicylic acid glucoside in xylem sap of <Emphasis Type="Italic">Brassica napus</Emphasis> infected with <Emphasis Type="Italic">Verticillium longisporum</Emphasis>

Salicylic acid (SA) and its glucoside (SAG) were detected in xylem sap of Brassica napus by HPLC–MS. Concentrations of SA and SAG in xylem sap from the root and hypocotyl of the plant, and in extracts of shoots above the hypocotyl, increased after infection with the vascular pathogen Verticillium longisporum. Both concentrations were correlated with disease severity assessed as the reduction in shoot length. Furthermore, SAG levels in shoot extracts were correlated with the amount of V. longisporum DNA in the hypocotyls. Although the concentration of SAG (but not SA) in xylem sap of infected plants gradually declined from 14 to 35 days post infection, SAG levels remained significantly higher than in uninfected plants during the whole experiment. Jasmonic acid (JA) and abscisic acid (ABA) levels in xylem sap were not affected by infection with V. longisporum. SA and SAG extend the list of phytohormones potentially transported from root to shoot with the transpiration stream. The physiological relevance of this transport and its contribution to the distribution of SA in plants remain to be elucidated.     

Heterologous expression of <Emphasis Type="Italic">Arabidopsis</Emphasis><Emphasis Type="Italic">NPR1</Emphasis> (<Emphasis Type="Italic">AtNPR1</Emphasis>) enhances oxidative stress tolerance in transgenic tobacco plants

In Arabidopsis, NPR1 (non-expressor of pathogenesis related genes 1, AtNPR1) functions downstream of salicylic acid (SA) and modulates the SA mediated systemic acquired resistance. It is also involved in a cross talk with the jasmonate pathway that is essential for resistance against herbivores and necrotrophic pathogens. Overexpression of AtNPR1 in transgenic plants resulted in enhanced disease resistance. Recently, tobacco transgenic plants expressing AtNPR1 were shown to be tolerant to the early instars of Spodoptera litura (Meur et al., Physiol Plant 133:765–775, 2008). In this communication, we show that the heterologous expression of AtNPR1 in tobacco has also enhanced the oxidative stress tolerance. The transgenic plants exhibited enhanced tolerance to the treatment with methyl viologen. This tolerance was associated with the constitutive upregulation of PR1, PR2 (glucanase), PR5 (thaumatin like protein), ascorbate peroxidase (APX) and Cu²⁺/Zn²⁺ superoxide dismutase (SOD). This is the first demonstration of the novel function of heterologous expression of AtNPR1 in oxidative stress tolerance in transgenic tobacco.     

Expression of the <Emphasis Type="Italic">yggE</Emphasis> gene protects <Emphasis Type="Italic">Escherichia coli</Emphasis> from potassium tellurite-generated oxidative stress

Potassium tellurite is highly toxic to most forms of life and specific bacterial tellurite defense mechanisms are not fully understood to date. Recent evidence suggests that tellurite would exert its toxic effects, at least in part, through the generation of superoxide anion that occurs concomitantly with intracellular tellurite (Te⁴⁺) reduction to elemental tellurium (Te^o). In this work the putative antioxidant role of YggE from Escherichia coli, a highly conserved protein in several bacterial species and whose function is still a matter of speculation, was studied. When exposed to tellurite, E. coli lacking yggE exhibited increased activity of superoxide dismutase and fumarase C, augmented levels of reactive oxygen species and high concentration of carbonyl groups in proteins. Upon genetic complementation with the homologous yggE gene these values were restored to those observed in the parental, isogenic, wild type strain, suggesting a direct participation of YggE in E. coli tolerance to tellurite.     

Galacturonic acid-induced changes in strawberry plant development <Emphasis Type="Italic">in vitro</Emphasis>

The oligogalacturonides derived from trifluoroacetic acid hydrolysis and their monomer galacturonic acid were tested for their effect on development of strawberry explants (Fragaria × ananassa) in vitro. The addition of oligogalacturonides or galacturonic acid in the plant tissue culture medium at concentrations of 0.1 or 1.0 mM increased shoot and leaf number in the presence of added benzyl adenine. The response to oligogalacturonides or galacturonic acid was maintained in the absence of benzyl adenine but was lessened. Conversely, root elongation was increased in the absence of benzyl adenine. A combined analysis of these experiments also indicated the increase in shoot or leaf number. High-performance anion exchange chromatography of the bioassayed oligogalacturonide samples using a pulsed amperometric detector revealed that the sample consisted of galactouronides with a degree of polymerization from 1 to 5 and the proportion of the monomer was very high (94%).     

Salicylic acid activates artemisinin biosynthesis in <Emphasis Type="Italic">Artemisia annua</Emphasis> L.

This paper provides evidence that salicylic acid (SA) can activate artemisinin biosynthesis in Artemisia annua L. Exogenous application of SA to A. annua leaves was followed by a burst of reactive oxygen species (ROS) and the conversion of dihydroartemisinic acid into artemisinin. In the 24 h after application, SA application led to a gradual increase in the expression of the 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) gene and a temporary peak in the expression of the amorpha-4,11-diene synthase (ADS) gene. However, the expression of the farnesyl diphosphate synthase (FDS) gene and the cytochrome P450 monooxygenase (CYP71AV1) gene showed little change. At 96 h after SA (1.0 mM) treatment, the concentration of artemisinin, artemisinic acid and dihydroartemisinic acid were 54, 127 and 72% higher than that of the control, respectively. Taken together, these results suggest that SA induces artemisinin biosynthesis in at least two ways: by increasing the conversion of dihydroartemisinic acid into artemisinin caused by the burst of ROS, and by up-regulating the expression of genes involved in artemisinin biosynthesis.     

Effect of salicylic acid potentiates cadmium-induced oxidative damage in <Emphasis Type="Italic">Oryza sativa</Emphasis> L. leaves

In the present investigation, we studied the possible potentiating effect of salicylic acid (SA) under Cd toxicity in Oryza sativa L. leaves. Cd treatments for 24 h reduced the shoot length, dry biomass and total chlorophyll content followed by high Cd accumulation in shoots. About 16 h presoaking with SA resulted in partial protection against Cd, as observed by minor changes in length, biomass and total chlorophyll. SA priming resulted in low Cd accumulation. Enhanced thiobarbituric acid reactive substances (TBARS), hydrogen peroxide (H₂O₂) and superoxide anion (O₂ ⁻) content were seen when Cd was applied alone, while under SA priming the extent of TBARS, H₂O₂ and O₂ ⁻ were significantly low, suggesting SA-regulated protection against oxidative stress. The antioxidant enzymes like Catalase (CAT), guaiacol peroxidase (GPx), glutathione reductase (GR) and superoxide dismutase (SOD) showed varied activities under Cd alone. CAT activity increased after Cd treatment, followed by a decline in GPX and GR activity. SOD also declined at the highest concentrations with an initial increase. Under SA-priming conditions, the efficiency of the antioxidant enzymes was significantly elevated. GPx and SOD activity showed significant increase in activity. The ascorbate activity increased after Cd treatment, followed by a decline in glutathione under SA-free condition. SA priming showed gradual increase in these non-enzymic antioxidants. Our results indicate that Cd-induced oxidative stress can be regulated by SA.     

<Emphasis Type="Italic">In vitro</Emphasis> minimum growth for conservation of <Emphasis Type="Italic">Drosophyllum lusitanicum</Emphasis>

The present paper reports a protocol for minimum growth conservation of Drosophyllum lusitanicum (L.) Link. in vitro. Double-node cuttings were maintained for 4, 8 and 12 months at 5 or 25 °C in the dark. The effects of sucrose either alone at 5, 20, 30, 40 and 60 g dm⁻³ or at 20, 40 and 60 g dm⁻³ in combination with 20 g dm⁻³ mannitol, on survival and post-storage shoot multiplication efficiency were investigated. The cultures could effectively be conserved under minimum growth at 5 °C for 8 months on Murashige and Skoog’s medium supplemented with 60 g dm⁻³ sucrose, 20 g dm⁻³ mannitol and 0.91 μM zeatin. Following extended conservation, the cultures could be successfully regenerated into new shoots, and they were morphologically similar to those of non-stored controls.     

Overexpression of Organellar and Cytosolic <Emphasis Type="Italic">AtHSP90</Emphasis> in <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> Impairs Plant Tolerance to Oxidative Stress

Three AtHSP90 isoforms, cytosol-localized AtHSP90.2, chloroplast-localized AtHSP90.5, and endoplasmic reticulum (ER)-localized AtHSP90.7 genes, were constitutively overexpressed in Arabidopsis thaliana to study their functional mechanisms under oxidative stress. Overexpression of AtHSP90 genes reduced germination of transgenic seeds under oxidative stress. When exposed to 10 mM H₂O₂, AtHSP90 transgenic seedlings displayed lower activities of superoxide dismutase, catalase, and peroxidase; higher content of malondialdehyde; and higher levels of protein damage than detected in the wild type. This indicated that overexpression of AtHSP90.2, AtHSP90.5, and AtHSP90.7 in Arabidopsis impaired plant tolerance to oxidative stress. Moreover, overexpression of chloroplast- and ER-localized AtHSP90 resulted in lower resistance to oxidative stress than that of cytosolic AtHSP90. This suggested that HSP90.2, HSP90.5, and HSP90.7 localized in different cellular compartments were involved in different functional mechanisms during oxidative stress.     

Suppression by ABA of salicylic acid and lignin accumulation and the expression of multiple genes,in <Emphasis Type="Italic">Arabidopsis</Emphasis> infected with <Emphasis Type="Italic">Pseudomonas syringae</Emphasis> pv. <Emphasis Type="Italic">tomato</Emphasis>

Abscisic acid (ABA) has been implicated in determining the outcome of interactions between many plants and their pathogens. We had previously shown that increased concentrations of ABA within leaves of Arabidopsis induced susceptibility towards an avirulent strain of Pseudomonas syringae pathovar (pv.) tomato. We now show that ABA induces susceptibility via suppression of the accumulation of components crucial for a resistance response. Lignin and salicylic acid concentrations in leaves were increased during a resistant interaction but reduced when plants were treated with ABA. The reduction in lignin and salicylic acid production was independent of the development of the hypersensitive response (HR), indicating that, in this host-pathogen system, HR is not required for resistance. Genome-wide gene expression analysis using microarrays showed that treatment with ABA suppressed the expression of many defence-related genes, including those important for phenylpropanoid biosynthesis and those encoding resistance-related proteins. Together, these results show that resistance induction in Arabidopsis to an avirulent strain of P. syringae pv. tomato is regulated by ABA. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

<Emphasis Type="Italic">Ty</Emphasis>1<Emphasis Type="Italic">/copia</Emphasis>- and <Emphasis Type="Italic">Ty</Emphasis>3<Emphasis Type="Italic">/gypsy</Emphasis>-like DNA sequences in <Emphasis Type="Italic">Helianthus </Emphasis>species

Two repeated DNA sequences isolated from a partial genomic DNA library of Helianthus annuus, p HaS13 and p HaS211, were shown to represent portions of the int gene of a Ty3 /gypsy retroelement and of the RNase-Hgene of a Ty1 /copia retroelement, respectively. Southern blotting patterns obtained by hybridizing the two probes to BglII- or DraI-digested genomic DNA from different Helianthus species showed p HaS13 and p HaS211 were parts of dispersed repeats at least 8 and 7 kb in length, respectively, that were conserved in all species studied. Comparable hybridization patterns were obtained in all species with p HaS13. By contrast, the patterns obtained by hybridizing p HaS211 clearly differentiated annual species from perennials. The frequencies of p HaS13- and p HaS211-related sequences in different species were 4.3x10(4)-1.3x10(5) copies and 9.9x10(2)-8.1x10(3) copies per picogram of DNA, respectively. The frequency of p HaS13-related sequences varied widely within annual species, while no significant difference was observed among perennial species. Conversely, the frequency variation of p HaS211-related sequences was as large within annual species as within perennials. Sequences of both families were found to be dispersed along the length of all chromosomes in all species studied. However, Ty3 /gypsy-like sequences were localized preferentially at the centromeric regions, whereas Ty1/ copia-like sequences were less represented or absent around the centromeres and plentiful at the chromosome ends. These findings suggest that the two sequence families played a role in Helianthusgenome evolution and species divergence, evolved independently in the same genomic backgrounds and in annual or perennial species, and acquired different possible functions in the host genomes.     

<Emphasis Type="Italic">Galleria</Emphasis><Emphasis Type="Italic">mellonella</Emphasis> are Resistant to <Emphasis Type="Italic">Pneumocystis</Emphasis><Emphasis Type="Italic">murina</Emphasis> Infection

Studying Pneumocystis has proven to be a challenge from the perspective of propagating a significant amount of the pathogen in a facile manner. The study of several fungal pathogens has been aided by the use of invertebrate model hosts. Our efforts to infect the invertebrate larvae Galleria mellonella with Pneumocystis proved futile since P. murina neither caused disease nor was able to proliferate within G. mellonella. It did, however, show that the pathogen could be rapidly cleared from the host.     

Seasonal changes in antioxidant activity,total phenolic and anthocyanin constituent of the stems of two <Emphasis Type="Italic">Morus</Emphasis> species (<Emphasis Type="Italic">Morus alba</Emphasis> L. and <Emphasis Type="Italic">Morus nigra</Emphasis> L.)

Seasonal changes of antioxidant activity, total phenolic and anthocyanin constituent of Morus nigra L. and Morus alba L. stems were investigated. Stems tissues of these species exhibited different antioxidant activity. Antioxidant action as well as anthocyanin constituents of these species reached the highest value in October whereas the lowest in February. Also, total phenolic constituents showed the similar pattern. An erratum to this article is available at .     

Physiological Responses of <Emphasis Type="Italic">Matricaria chamomilla</Emphasis> to Potassium Nitrate Supply and Foliar Application of Ethephon

The study is focused on changes in metabolism of Matricaria chamomilla, caused by potassium nitrate (KNO₃) supplement and foliar application of an ethylene releaser—ethephon (ET). ET-treated plants were irrigated with 0, 9, 18 or 27 mmol of KNO₃ during 1 week and simultaneously treated with ET. The same procedure was followed with ET non-treated plants, where an equal amount of distilled water was sprayed on leaves. Nitrogen addition into soil substrate caused considerable increment in dry matter content, nitrate accumulation and amino acids synthesis. After ET application, a positive correlation between KNO₃ supply and stress-related parameters, such as superoxide radical, hydrogen peroxide and malondialdehyde was found. Experimental conditions led to a sharp decrease in herniarin level, which was accompanied with increasing content of its glycosidic precursors in ET-treated plants. The observations indicated that higher doses of nitrate suppressed the stimulation effect of ET on the production of salicylic acid and umbelliferone, metabolites, which are involved in stress responses in plants. In the case of umbelliferone, ET strongly induced its accumulation in comparison with ET non-treated variants.     

Revision of the <Emphasis Type="Italic">Serrulati</Emphasis> species of <Emphasis Type="Italic">Penstemon</Emphasis> section <Emphasis Type="Italic">Saccanthera</Emphasis> subsection <Emphasis Type="Italic">Serrulati</Emphasis>

A revision of Penstemon sect. Saccanthera subsect. Serrulati includes a new species (P. salmonensis), a new variety (P. triphyllus var. infernalis), and the elevation of a subspecies to species (P. curtiflorus), bringing the total number of species to eight, which are keyed and described, complete with nomenclature and type citations.     

Stimulation of indoleacetic acid production in a <Emphasis Type="Italic">Rhizobium</Emphasis> isolate of <Emphasis Type="Italic">Vigna mungo</Emphasis> by root nodule phenolic acids

The influence of endogenous root nodules phenolic acids on indoleacetic acid (IAA) production by its symbiont (Rhizobium) was examined. The root nodules contain higher amount of IAA and phenolic acids than non-nodulated roots. Presence of IAA metabolizing enzymes, IAA oxidase, peroxidase, and polyphenol oxidase indicate the metabolism of IAA in the nodules and roots. Three most abundant endogenous root nodule phenolic acids (protocatechuic acid, 4-hydroxybenzaldehyde and p-coumaric acid) have been identified and their effects on IAA production by the symbiont have been studied in l-tryptophan supplemented yeast extract basal medium. Protocatechuic acid (1.5 μg ml⁻¹) showed maximum stimulation (2.15-fold over control) of IAA production in rhizobial culture. These results indicate that the phenolic acids present in the nodule might serve as a stimulator for IAA production by the symbiont (Rhizobium). Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. An erratum to this article can be found at     

<Emphasis Type="Italic">Agrobacterium</Emphasis><Emphasis Type="Italic">tumefaciens</Emphasis>-mediated transformation of callus cells of <Emphasis Type="Italic">Crataegus</Emphasis><Emphasis Type="Italic">aronia</Emphasis>

A genetic transformation system has been developed for callus cells of Crataegus aronia using Agrobacterium tumefaciens. Callus culture was established from internodal stem segments incubated on Murashige and Skoog (MS) medium supplemented with 5 mg l⁻¹ Indole-3-butyric acid (IBA) and 0.5 mg l⁻¹ 6-benzyladenine (BA). In order to optimize the callus culture system with respect to callus growth and coloration, different types and concentrations of plant growth regulators were tested. Results indicated that the best average fresh weight of red colored callus was obtained on MS medium supplemented with 2 mg l⁻¹ 2,4-dichlorophenoxyacetic acid (2,4-D) and 1.5 mg l⁻¹ kinetin (Kin) (callus maintenance medium). Callus cells were co-cultivated with Agrobacterium harboring the binary plasmid pCAMBIA1302 carrying the mgfp5 and hygromycin phosphotransferase (hptII) genes conferring green fluorescent protein (GFP) activity and hygromycin resistance, respectively. Putative transgenic calli were obtained 4 weeks after incubation of the co-cultivated explants onto maintenance medium supplemented with 50 mg l⁻¹ hygromycin. Molecular analysis confirmed the integration of the transgenes in transformed callus. To our knowledge, this is the first time to report an Agrobacterium-mediated transformation system in Crataegus aronia.