Specific patterns of changes in wheat gene expression after treatment with three antifungal compounds

Elicitor-Driven Defense Mechanisms: Shielding Cotton Plants against the Onslaught of Cotton Leaf Curl Multan Virus (CLCuMuV) Disease

Salicylic acid (SA), benzothiadiazole (BTH), and methyl jasmonate (MeJA) are potential elicitors found in plants, playing a crucial role against various biotic and abiotic stresses. The systemic acquired resistance (SAR) mechanism was evaluated in cotton plants for the suppression of Cotton leaf curl Multan Virus (CLCuMuV) by the exogenous application of different elicitors. Seven different treatments of SA, MeJA, and BTH were applied exogenously at different concentrations and combinations. In response to elicitors treatment, enzymatic activities such as SOD, POD, CAT, PPO, PAL, β-1,3 glucanse, and chitinase as biochemical markers for resistance were determined from virus-inoculated and uninoculated cotton plants of susceptible and tolerant varieties, respectively. CLCuMuV was inoculated on cotton plants by whitefly (Bemesia tabaci biotype Asia II-1) and detected by PCR using specific primers for the coat protein region and the Cotton leaf curl betasatellite (CLCuMuBV)-associated component of CLCuMuV. The development of disease symptoms was observed and recorded on treated and control plants. The results revealed that BTH applied at a concentration of 1.1 mM appeared to be the most effective treatment for suppressing CLCuMuV disease in both varieties. The enzymatic activities in both varieties were not significantly different, and the disease was almost equally suppressed in BTH-treated cotton plants following virus inoculation. The beta satellite and coat protein regions of CLCuMuV were not detected by PCR in the cotton plants treated with BTH at either concentration. Among all elicitors, 1.1 mM BTH was proven to be the best option for inducing resistance after the onset of CLCuMuV infection and hence it could be part of the integrated disease management program against Cotton leaf curl virus.

Modulation of defense genes and phenolic compounds in wild blueberry in response to Botrytis cinerea under field conditions

Botrytis blight is an important disease of wild blueberry [(Vaccinium angustifolium (Va) and V. myrtilloides (Vm))] with variable symptoms in the field due to differences in susceptibility among blueberry phenotypes. Representative blueberry plants of varying phenotypes were inoculated with spores of B. cinerea. The relative expression of pathogenesis-related genes (PR3, PR4), flavonoid biosynthesis genes, and estimation of the concentration of ten phenolic compounds between uninoculated and inoculated samples at different time points were analyzed. Representative plants of six phenotypes (brown stem Va, green stem Va, Va f. nigrum, tall, medium, and short stems of Vm) were collected and studied using qRT-PCR. The expression of targeted genes indicated a response of inoculated plants to B. cinerea at either 12, 24, 48 or 96 h post inoculation (hpi). The maximum expression of PR3 occurred at 24 hpi in all the phenotypes except Va f. nigrum and tall stem Vm. Maximum expression of both PR genes occurred at 12 hpi in Va f. nigrum. Chalcone synthase, flavonol synthase and anthocyanin synthase were suppressed at 12 hpi followed by an upregulation at 24 hpi. The expression of flavonoid pathway genes was phenotype-specific with their regulation patterns showing temporal differences among the phenotypes. Phenolic compound accumulation was temporally regulated at different post-inoculation time points. M-coumaric acid and kaempferol-3-glucoside are the compounds that were increased with B. cinerea inoculation. Results from this study suggest that the expression of PR and flavonoid genes, and the accumulation of phenolic compounds associated with B. cinerea infection could be phenotype specific. This study may provide a starting point for understanding and determining the mechanisms governing the wild blueberry-B. cinerea pathosystem.

Application of exogenous salicylic acid reduces disease severity of Plasmodiophora brassicae in pakchoi (Brassica campestris ssp. chinensis Makino)

Clubroot is one of the most serious diseases affecting Brassicaceae plants worldwide. However, there is no effective control method for clubroot. Salicylic acid (SA) is a plant hormone that plays a critical role in plant defense. In our study, we found the disease severity of a clubroot-sensitive cultivar of pakchoi, Xinxiaqing, was reduced with 0.6mM exogenous SA after the infection of P. brassicae. To investigate the mechanism of SA-reduced disease severity against clubroot, then we analyzed the plant growth, alteration of antioxidant enzyme system, and related gene expression of Xinxiaqing. Results showed that the clubroot incidence rate and disease index were decreased after being treated with 0.6 mM exogenous SA. Furthermore, plant growth, reactive oxygen species (ROS) contents, and membrane lipid peroxidation were changed. The activities of antioxidant enzymes, including superoxide dismutase (SOD), ascorbic acid-peroxidase (APX), catalase (CAT), and glutathione reductase (GR), were increased. Additionally, the production rates of malondialdehyde (MDA), hydrogen peroxide (H2O2), and superoxide anion (O2·-) were also inhibited. The expression levels of genes, encoding SOD, APX, CAT, and GR, were increased. By summering all results, we conclude that 0.6 mM SA contributes to the reduction of disease severity to clubroot by increasing the activities of antioxidant enzymes, abilities of osmotic regulation, and ROS scavenging to reduce the clubroot-induced damage in pakchoi.

Antioxidant and α-Glucosidase Inhibitory Activities Guided Isolation and Identification of Components from Mango Seed Kernel

In the present study, petroleum ether, dichloromethane, ethyl acetate, and n-butanol fractions of mango seed kernel exhibited different degrees of antioxidant and α-glucosidase inhibitory activity. Thus, quantitative and qualitative analysis of the petroleum ether fraction was conducted by GC-MS. Among identified components, four unsaturated fatty acids had never been reported in natural products before, together with 19 known components. In addition, 17 compounds were isolated and elucidated from other active fractions. Compounds 2, 9, 15, and 17 were isolated for the first time from Mangifera genus. Compounds 1 and 2 exhibited prominent DPPH radical scavenging and α-glucosidase inhibitory effects. In order to further explore their mechanism of α-glucosidase inhibition, their enzyme kinetics and in silico modeling experiments were performed. The results indicated that 1 inhibited α-glucosidase in a noncompetitive manner, whereas 2 acted in a competitive manner. In molecular docking, the stability of binding was enhanced by π-π T-shaped, π-alkyl, π-π stacked, hydrogen bond, and electrostatic interactions. Thus, compounds 1 and 2 were determined to be new potent antioxidant and α-glucosidase inhibitors for preventing food oxidation and enhancing hypoglycemic activity.

Berberine induces resistance against tobacco mosaic virus in tobacco

BACKGROUND

Plant systemic resistance induced by botanical compounds is a promising alternative method of disease management. The natural product berberine, usually used as an antimicrobial in medicine, has been proven to have antifungal activity in agriculture. To investigate the induced resistance imparted by berberine, the effect of berberine against tobacco mosaic virus (TMV) and the mechanism governing this effect were determined.

RESULT

Berberine exhibited considerable in vivo anti-TMV activity of up to 68.3% but had no in vitro direct effect on TMV. Moreover, berberine could induce immune responses against TMV in tobacco, including the hypersensitive reaction (HR), accumulation of H2 O2 , increases in defense enzymes and overexpression of pathogenesis-related (PR) proteins. In addition, upregulation of salicylic acid (SA) biosynthesis genes PAL, CM1, ICS, PBS3 and the enzyme benzoic acid 2-hydroxylase (BA2H) confirmed that SA was involved in the defensive signals. Berberine can induce crop resistance against TMV, Phytophthora nicotianae, Botrytis cinerea and Blumeria graminis in the greenhouse.

CONCLUSION

This paper highlights the use of berberine in manipulating tobacco to generate defense responses against TMV, which can be attributed to SA-mediated induced resistance. The paper provides a theoretical basis for the application of berberine as a resistance activator and for further research on induced resistance by botanical natural product. © 2019 Society of Chemical Industry.

Bismerthiazol Inhibits Xanthomonas citri subsp. citri Growth and Induces Differential Expression of Citrus Defense-Related Genes

Citrus canker, caused by Xanthomonas citri ssp. citri, is a serious disease that causes substantial economic losses to the citrus industry worldwide. The bactericide bismerthiazol has been used to control rice bacterial blight (X. oryzae pv. oryzae). In this paper, we demonstrate that bismerthiazol can effectively control citrus canker by both inhibiting the growth of X. citri ssp. citri and triggering the plant's host defense response through the expression of several pathogenesis-related genes (PR1, PR2, CHI, and RpRd1) and the nonexpresser of PR genes (NPR1, NPR2, and NPR3) in 'Duncan' grapefruit, especially at early treatment times. In addition, we found that bismerthiazol induced the expression of the marker genes CitCHS and CitCHI in the flavonoid pathway and the PAL1 (phenylalanine ammonia lyase 1) gene in the salicylic acid (SA) biosynthesis pathway at different time points. Moreover, bismerthiazol also induced the expression of the priming defense-associated gene AZI1. Taken together, these results indicate that the induction of the defense response in 'Duncan' grapefruit by bismerthiazol may involve the SA signaling pathway and the priming defense and that bismerthiazol may serve as an alternative to copper bactericides for the control of citrus canker.

Bactérias endofíticas como agentes de controle biológico na orizicultura

RESUMO Esta publicação apresenta alguns dados sobre as interações entre as bactérias e as plantas hospedeiras, considerando os simbiontes e os patógenos das plantas de importância agrícola, com ênfase nos agroecossistemas de arroz irrigado. Neste trabalho foram abordados aspectos relacionados a essas bactérias endofíticas, tais como: (i) endofíticos e suas interações com as plantas cultivadas; (ii) rizobactérias promotoras do crescimento vegetal [plant growth-promoting rhizobacteria (PGPR)] e sua aplicabilidade no controle biológico; (iii) bactérias endofíticas versus PGPR no controle biológico de fitopatógenos; (iv) aplicação de recombinantes endofíticos na agrobiotecnologia. No final do artigo estão apresentadas as opiniões e perspectivas dos autores sobre as bactérias que vivem associadas às plantas cultivadas nos agroecossistemas.

Rice transcriptome analysis to identify possible herbicide quinclorac detoxification genes

Quinclorac is a highly selective auxin-type herbicide and is widely used in the effective control of barnyard grass in paddy rice fields, improving the world's rice yield. The herbicide mode of action of quinclorac has been proposed, and hormone interactions affecting quinclorac signaling has been identified. Because of widespread use, quinclorac may be transported outside rice fields with the drainage waters, leading to soil and water pollution and other environmental health problems. In this study, we used 57K Affymetrix rice whole-genome array to identify quinclorac signaling response genes to study the molecular mechanisms of action and detoxification of quinclorac in rice plants. Overall, 637 probe sets were identified with differential expression levels under either 6 or 24 h of quinclorac treatment. Auxin-related genes such as GH3 and OsIAAs responded to quinclorac treatment. Gene Ontology analysis showed that genes of detoxification-related family genes were significantly enriched, including cytochrome P450, GST, UGT, and ABC and drug transporter genes. Moreover, real-time RT-PCR analysis showed that top candidate genes of P450 families such as CYP81, CYP709C, and CYP72A were universally induced by different herbicides. Some Arabidopsis genes of the same P450 family were up-regulated under quinclorac treatment. We conducted rice whole-genome GeneChip analysis and the first global identification of quinclorac response genes. This work may provide potential markers for detoxification of quinclorac and biomonitors of environmental chemical pollution.

Foliar application of isopyrazam and epoxiconazole improves photosystem II efficiency, biomass and yield in winter wheat

A range of fungicides including epoxiconazole, azoxystrobin and isopyrazam, were applied to winter wheat at GS 31/32 to determine their effect on photosystem II (PSII) efficiency, biomass and yield. Frequent, repeated measurements of chlorophyll fluorescence were carried on plants grown under different water regimes in controlled environment and in the field to establish the transiency of fluorescence changes in relation to fungicide application. Application of the succinate dehydrogenase inhibitor isopyrazam in a mixture with the triazole epoxiconazole increased PSII efficiency associated with a 28% increase in biomass in the controlled environment and 4% increase in grain yield in the field in the absence of disease pressure. Application of isopyrazam and epoxiconazole increased efficiency of PSII photochemistry (Fv'/Fm') as early as 4h following application associated with improved photosynthetic gas exchange and increased rates of electron transport. We reveal a strong, positive relationship between Fv'/Fm' and CO2 assimilation rate, stomatal conductance and transpiration rate in controlled environment and Fv'/Fm' detected just after anthesis on the flag leaf at GS 73 and grain yield in field. We conclude that application of a specific combination of fungicides with positive effects of plant physiology in the absence of disease pressure results in enhanced biomass and yield in winter wheat. Additionally, an accurate and frequent assessment of photosynthetic efficiency of winter wheat plants can be used to predict yield and biomass in the field.

Avocado roots treated with salicylic acid produce phenol-2,4-bis (1,1-dimethylethyl), a compound with antifungal activity

We demonstrated the ability of salicylic acid (SA) to induce a compound in avocado roots that strengthens their defense against Phytophthora cinnamomi. The SA content of avocado roots, before and after the application of exogenous SA, was determined by High-Performance Liquid Chromatography (HPLC). After 4h of SA feeding, the endogenous level in the roots increased to 223 μg g(-1) FW, which was 15 times the amount found in control roots. The methanolic extract obtained from SA-treated avocado roots inhibited the radial growth of P. cinnamomi. A thin layer chromatographic bioassay with the methanolic extract and spores of Aspergillus showed a distinct inhibition zone. The compound responsible for the inhibition was identified as phenol-2,4-bis (1,1-dimethylethyl) by gas chromatography and mass spectrometry. At a concentration of 100 μg/mL, the substance reduced germinative tube length in Aspergillus and radial growth of P. cinnamomi. A commercial preparation of phenol-2,4-bis (1,1-dimethylethyl) caused the same effects on mycelium morphology and radial growth as our isolate, confirming the presence of this compound in the root extracts. This is the first report of the induction of this compound in plants by SA, and the results suggest that it plays an important role in the defense response of avocado.

Development of disease-resistant rice using regulatory components of induced disease resistance

Infectious diseases cause huge crop losses annually. In response to pathogen attacks, plants activate defense systems that are mediated through various signaling pathways. The salicylic acid (SA) signaling pathway is the most powerful of these pathways. Several regulatory components of the SA signaling pathway have been identified, and are potential targets for genetic manipulation of plants' disease resistance. However, the resistance associated with these regulatory components is often accompanied by fitness costs; that is, negative effects on plant growth and crop yield. Chemical defense inducers, such as benzothiadiazole and probenazole, act on the SA pathway and induce strong resistance to various pathogens without major fitness costs, owing to their 'priming effect.' Studies on how benzothiadiazole induces disease resistance in rice have identified WRKY45, a key transcription factor in the branched SA pathway, and OsNPR1/NH1. Rice plants overexpressing WRKY45 were extremely resistant to rice blast disease caused by the fungus Magnaporthe oryzae and bacterial leaf blight disease caused by Xanthomonas oryzae pv. oryzae (Xoo), the two major rice diseases. Disease resistance is often accompanied by fitness costs; however, WRKY45 overexpression imposed relatively small fitness costs on rice because of its priming effect. This priming effect was similar to that of chemical defense inducers, although the fitness costs were amplified by some environmental factors. WRKY45 is degraded by the ubiquitin-proteasome system, and the dual role of this degradation partly explains the priming effect. The synergistic interaction between SA and cytokinin signaling that activates WRKY45 also likely contributes to the priming effect. With a main focus on these studies, I review the current knowledge of SA-pathway-dependent defense in rice by comparing it with that in Arabidopsis, and discuss potential strategies to develop disease-resistant rice using signaling components.

Controlling crop diseases using induced resistance: challenges for the future

A number of different types of induced resistance have been defined based on differences in signalling pathways and spectra of effectiveness, including systemic acquired resistance and induced systemic resistance. Such resistance can be induced in plants by application of a variety of biotic and abiotic agents. The resulting resistance tends to be broad-spectrum and can be long-lasting, but is rarely complete, with most inducing agents reducing disease by between 20 and 85%. Since induced resistance is a host response, its expression under field conditions is likely to be influenced by a number of factors, including the environment, genotype, crop nutrition and the extent to which plants are already induced. Although research in this area has increased over the last few years, our understanding of the impact of these influences on the expression of induced resistance is still poor. There have also been a number of studies in recent years aimed at understanding of how best to use induced resistance in practical crop protection. However, such studies are relatively rare and further research geared towards incorporating induced resistance into disease management programmes, if appropriate, is required.

Broad-spectrum acquired resistance in barley induced by the Pseudomonas pathosystem shares transcriptional components with Arabidopsis systemic acquired resistance

Inducible resistance responses play a central role in the defense of plants against pathogen attack. Acquired resistance (AR) is induced alongside defense toward primary attack, providing broad-spectrum protection against subsequent pathogen challenge. The localization and molecular basis of AR in cereals is poorly understood, in contrast with the well-characterized systemic acquired resistance (SAR) response in Arabidopsis. Here, we use Pseudomonas syringae as a biological inducer of AR in barley, providing a clear frame of reference to the Arabidopsis-P. syringae pathosystem. Inoculation of barley leaf tissue with the nonadapted P. syringae pv. tomato avrRpm1 (PstavrRpm1) induced an active local defense response. Furthermore, inoculation of barley with PstavrRpm1 resulted in the induction of broad-spectrum AR at a distance from the local lesion, "adjacent" AR, effective against compatible isolates of P. syringae and Magnaporthe oryzae. Global transcriptional profiling of this adjacent AR revealed similarities with the transcriptional profile of SAR in Arabidopsis, as well as transcripts previously associated with chemically induced AR in cereals, suggesting that AR in barley and SAR in Arabidopsis may be mediated by analogous pathways.

Salicylic acid derivatives: synthesis, features and usage as therapeutic tools

INTRODUCTION

In the field of medicinal chemistry, there is a growing interest in the use of small molecules. Although acetyl salicylic acid is well known for medical applications, little is known about other salicylic acid derivatives, and there is serious lack of data and information on the effects and biological evaluation that connect them.

AREAS COVERED

This review covers the synthesis and drug potencies of salicylic acid derivatives. After a brief overview of the information on salicylic acid and its features, a detailed review of salicylic acids as drugs and prodrugs, usage as cyclooxygenase inhibitors, properties in plants, synthesis and recent patents, is developed.

EXPERT OPINION

Salicylic acid research is still an important area and innovations continue to arise, which offer hope for new therapeutics in related fields. It is anticipated that this review will guide the direction of long-term drug/nutraceutical safety trials and stimulate ideas for future research.

Greater antioxidant and respiratory metabolism in field-grown soybean exposed to elevated O3 under both ambient and elevated CO2

Antioxidant metabolism is responsive to environmental conditions, and is proposed to be a key component of ozone (O(3)) tolerance in plants. Tropospheric O(3) concentration ([O(3)]) has doubled since the Industrial Revolution and will increase further if precursor emissions rise as expected over this century. Additionally, atmospheric CO(2) concentration ([CO(2)]) is increasing at an unprecedented rate and will surpass 550 ppm by 2050. This study investigated the molecular, biochemical and physiological changes in soybean exposed to elevated [O(3) ] in a background of ambient [CO(2)] and elevated [CO(2)] in the field. Previously, it has been difficult to demonstrate any link between antioxidant defences and O(3) stress under field conditions. However, this study used principle components analysis to separate variability in [O(3)] from variability in other environmental conditions (temperature, light and relative humidity). Subsequent analysis of covariance determined that soybean antioxidant metabolism increased with increasing [O(3)], in both ambient and elevated [CO(2)]. The transcriptional response was dampened at elevated [CO(2)], consistent with lower stomatal conductance and lower O(3) flux into leaves. Energetically expensive increases in antioxidant metabolism and tetrapyrrole synthesis at elevated [O(3)] were associated with greater transcript levels of enzymes involved in respiratory metabolism.

Salicylic acid and its function in plant immunity

The small phenolic compound salicylic acid (SA) plays an important regulatory role in multiple physiological processes including plant immune response. Significant progress has been made during the past two decades in understanding the SA-mediated defense signaling network. Characterization of a number of genes functioning in SA biosynthesis, conjugation, accumulation, signaling, and crosstalk with other hormones such as jasmonic acid, ethylene, abscisic acid, auxin, gibberellic acid, cytokinin, brassinosteroid, and peptide hormones has sketched the finely tuned immune response network. Full understanding of the mechanism of plant immunity will need to take advantage of fast developing genomics tools and bioinformatics techniques. However, elucidating genetic components involved in these pathways by conventional genetics, biochemistry, and molecular biology approaches will continue to be a major task of the community. High-throughput method for SA quantification holds the potential for isolating additional mutants related to SA-mediated defense signaling.

Cultivar Effects on the Expression of Induced Resistance in Spring Barley

The influence of host genotype on the expression of induced resistance was examined in several cultivars of spring barley (Hordeum vulgare). Induced resistance was activated using a combination of elicitors (acibenzolar- S-methyl, β-aminobutyric acid, and cis-jasmone) shown in previous work to induce resistance effectively in barley. The barley cultivars examined were Cellar, Chalice, Decanter, Oxbridge, Tipple, Troon, and Westminster, which differed in their genetic resistance to two major pathogens of barley, Rhynchosporium secalis and Blumeria graminis f. sp. hordei. Controlled-environment studies showed that, although the elicitor combination reduced levels of R. secalis in all but one cultivar, the magnitude of the reduction differed among cultivars. Similar results were obtained in field experiments in 2007, 2008, and 2009, although there was inconsistency in cultivar effects between years, with the elicitor providing disease control in some cultivars in some years and not others. Use of the elicitor combination produced no significant effect on grain yield compared with untreated plants in most cases, although significant increases in grain yield were obtained with the elicitor treatment in two cultivars in 2007 and one cultivar in 2009. Analysis of the defense-related enzyme cinnamyl alcohol dehydrogenase in leaf samples from the field experiment in 2007 showed that activity of the enzyme was already high prior to elicitor application, although activity was increased further in one cultivar following elicitor treatment. It is possible, therefore, that these plants were already induced. Further work is required to confirm this and to determine whether prior induction has any bearing on the variable disease control obtained from elicitors in spring barley.

Botryticides affect grapevine leaf photosynthesis without inducing defense mechanisms

The effects of the two botryticides, fludioxonil (fdx) and fenhexamid (fhd), were investigated on grapevine leaves (Vitis vinifera L. cv. Pinot noir) following photosynthesis and defense mechanisms. Treatments were carried out in vineyard at the end of flowering. Phytotoxicity of both fungicides was evaluated by measuring variations of leaf photosynthetic parameters and correlated expression of photosynthesis-related genes. Results demonstrated that similar decrease in photosynthesis was caused by fdx and fhd applications. Moreover, the mechanism leading to photosynthesis alteration seems to be the same for both fungicides. Stomatal limitation to photosynthetic gas exchange did not change following treatments indicating that inhibition of photosynthesis was mostly attributed to non-stomatal factors. Nevertheless, fungicides-induced depression of photosynthesis was related neither to a decrease in Rubisco carboxylation efficiency and in the capacity for regeneration of ribulose 1,5-bisphosphate nor to loss in PSII activity. However, fdx and fhd treatments generated repression of genes encoding proteins involved in the photosynthetic process. Indeed, decreased photosynthesis was coupled with repression of PsbP subunit of photosystem II (psbP1), chlorophyll a/b binding protein of photosystem I (cab) and Rubisco small subunit (rbcS) genes. A repression of these genes may participate in the photosynthesis alteration. To our knowledge, this is the first study of photosynthesis-related gene expression following fungicide stress. In the meantime, defense responses were followed by measuring chitinase activity and expression of varied defense-related genes encoding proteins involved in phenylpropanoid synthesis (PAL) or octadecanoid synthesis (LOX), as well as pathogenesis-related protein (Chi4C). No induction of defense was observed in botryticides-treated leaves. To conclude, the photosynthesis is affected without any triggering of plant defense responses.

Differential expression of genes in soybean in response to the causal agent of Asian soybean rust (Phakopsora pachyrhizi Sydow) is soybean growth stage-specific

Understanding plant host response to a pathogen such as Phakopsora pachyrhizi, the causal agent of Asian soybean rust (ASR), under different environmental conditions and growth stages is crucial for developing a resistant plant variety. The main objective of this study was to perform global transcriptome profiling of P. pachyrhizi-exposed soybean (Glycine max) with susceptible reaction to the pathogen from two distinct developmental growth stages using whole genome Affymetrix microarrays of soybean followed by confirmation using a resistant genotype. Soybean cv. 5601T (susceptible to ASR) at the V(4) and R(1) growth stages and Glycine tomentella (resistant to ASR) plants were inoculated with P. pachyrhizi and leaf samples were collected after 72 h of inoculation for microarray analysis. Upon analyzing the data using Array Assist software at 5% false discovery rate (FDR), a total of 5,056 genes were found significantly differentially expressed at V(4) growth stage, of which 2,401 were up-regulated, whereas 579 were found differentially expressed at R(1) growth stage, of which 264 were up-regulated. There were 333 differentially expressed common genes between the V(4) and R(1) growth stages, of which 125 were up-regulated. A large difference in number of differentially expressed genes between the two growth stages indicates that the gene expression is growth-stage-specific. We performed real-time RT-PCR analysis on nine of these genes from both growth stages and both plant species and found results to be congruent with those from the microarray analysis.

Benzothiadiazole affects the leaf proteome in arctic bramble (Rubus arcticus)

Benzothiadiazole (BTH) induces resistance to the downy mildew pathogen, Peronospora sparsa, in arctic bramble, but the basis for the BTH-induced resistance is unknown. Arctic bramble cv. Mespi was treated with BTH to study the changes in leaf proteome and to identify proteins with a putative role in disease resistance. First, BTH induced strong expression of one PR-1 protein isoform, which was also induced by salicylic acid (SA). The PR-1 was responsive to BTH and exogenous SA despite a high endogenous SA content (20-25 microg/g fresh weight), which increased to an even higher level after treatment with BTH. Secondly, a total of 792 protein spots were detected in two-dimensional gel electrophoresis, eight proteins being detected solely in the BTH-treated plants. BTH caused up- or down-regulation of 72 and 31 proteins, respectively, of which 18 were tentatively identified by mass spectrometry. The up-regulation of flavanone-3-hydroxylase, alanine aminotransferase, 1-aminocyclopropane-1-carboxylate oxidase, PR-1 and PR-10 proteins may partly explain the BTH-induced resistance against P. sparsa. Other proteins with changes in intensity appear to be involved in, for example, energy metabolism and protein processing. The decline in ATP synthase, triosephosphate isomerase, fructose bisphosphate aldolase and glutamine synthetase suggests that BTH causes significant changes in primary metabolism, which provides one possible explanation for the decreased vegetative growth of foliage and rhizome observed in BTH-treated plants.

Hapten synthesis and monoclonal antibody-based immunoassay development for the detection of the fungicide kresoxim-methyl

Strobilurin fungicides have been increasingly used for fungus pest control since they were introduced in 1996. For pesticide residue detection, immunoassays constitute nowadays a valuable approach. This paper describes the synthesis of functionalized haptens of kresoxim-methyl, the production of monoclonal antibodies, and the development of enzyme-linked immunosorbent assays. On the one hand, a two-step conjugate-coated immunoassay was optimized using extended or short incubation times, with limits of detection of 0.4 ng/mL for the extended assay and 0.3 ng/mL for the rapid assay. On the other hand, an immunoassay was optimized following a procedure consisting of just one incubation step. This one-step assay had a limit of detection of 0.4 ng/mL. All of these assays showed a similar performance, with sensitivities well below common maximum residue limits for this pesticide (50 microg/kg) and lower than the detection limits of the usual chromatographic detection methods.

Systemic and local modulation of plant responses by Piriformospora indica and related Sebacinales species

Piriformospora indica is a fungus of the order Sebacinales (Basidiomycota) infesting roots of mono- and dicotyledonous plants. Endophytic fungal colonization leads to enhanced plant growth while host cell death is required for proliferation in differentiated root tissue to form a mutualistic interaction. Colonization of barley roots by P. indica and related Sebacina vermifera strains also leads to systemic resistance against the leaf pathogenic fungus Blumeria graminis f.sp. hordei due to a yet unknown mechanism of induced resistance. In order to elucidate plant response pathways governed by these root endophytes, we analyzed gene expression in barley plants exhibiting an established symbiosis with P. indica 3 weeks after inoculation. P. indica-colonized roots showed no induction of defence-related genes, while other genes showed a differential regulation pattern indicating a faster P. indica-dependent root development. Gene expression analysis of leaves detected only few systemically induced mRNAs. Among differentially regulated transcripts, we characterized the pathogenesis-related gene HvPr17b and the molecular chaperone HvHsp70 in more detail. HvPr17b shows similarity with TaWCI5, a wheat gene inducible by chemical resistance inducers and salicylate, and was previously proven to exhibit antifungal activity against B. graminis. HvHsp70 is the first gene found to systemically indicate root colonization with endophytic fungi of the order Sebacinales. Both genes are discussed as markers for endophytic colonization and resulting systemic responses.

Evaluation of plant activator and chemical fungicides on leaf blight (Bipolaris sorokiniana) development and yield of wheat

Bion 50 WG (Benzothiodiazole), Tilt-250 EC (Propiconazole) and Amistar (Azoxystrobin) either alone and some of their combinations were evaluated against leaf blight/spot (Bipolaris sorokiniana) development and yield of wheat. All the treatments significantly reduced leaf spot reaction of wheat over untreated control. But Bion in combination with Amistar resulted significantly highest reduction of leaf spot reaction of wheat (p = 0.05) against all the tested pathotypes inoculated at flag leaf stage. In the field, Bion reduced leaf spot severity at heading and flowering stage in 2000-2001 and at hard dough stage in 2001-2002. Number of grains/ear not significantly increased by treating seeds with Bion though 1000-grain weight is significantly increased (p = 0.05) in 2000-2001 by Bion. Statistically higher grain yield was obtained from the experimental plot by treating seeds with Bion and Amistar. Bion resulted 53.33% higher grain yield in compare to untreated control.

Common and distinct gene expression patterns induced by the herbicides 2,4-dichlorophenoxyacetic acid, cinidon-ethyl and tribenuron-methyl in wheat

In wheat, herbicides are used to control weeds. Little is known about the changes induced in the metabolism of tolerant plants after herbicide treatment. The impact of three herbicides [2,4-dichlorophenoxyacetic acid (2,4-D), cinidon-ethyl and tribenuron-methyl] on the wheat transcriptome was studied using cDNA microarrays. Gene expression of plants grown in a controlled environment or in the field was studied between 24 h and 2 weeks after treatment. Under controlled conditions, 2,4-D induced genes of the phenylpropanoid pathway soon after treatment. Cinidon-ethyl triggered peroxidase and defence-related gene expression under controlled conditions, probably because reactive oxygen species are released by photo-oxidation of protoporphyrin-IX. The same genes were upregulated in the field as under controlled conditions, albeit at a weaker level. These results show that cinidon-ethyl specifically induces genes involved in plant defence. Under controlled conditions, tribenuron-methyl did not change the expression profile immediately after treatment, but defence-related genes were upregulated after 1 week. Sulfonylurea compounds such as tribenuron-methyl specifically inhibit acetolactate synthase and are rapidly detoxified, but the activity of some of the resulting metabolites could explain later changes in gene expression. Finally, overexpression of the isopropylmalate synthase gene, involved in branched-chain amino acid synthesis, and of defence-related genes was observed in the field after sulfonylurea treatment.

RNA interference-based gene silencing as an efficient tool for functional genomics in hexaploid bread wheat

Insertional mutagenesis and gene silencing are efficient tools for the determination of gene function. In contrast to gain- or loss-of-function approaches, RNA interference (RNAi)-induced gene silencing can possibly silence multigene families and homoeologous genes in polyploids. This is of great importance for functional studies in hexaploid wheat (Triticum aestivum), where most of the genes are present in at least three homoeologous copies and conventional insertional mutagenesis is not effective. We have introduced into bread wheat double-stranded RNA-expressing constructs containing fragments of genes encoding Phytoene Desaturase (PDS) or the signal transducer of ethylene, Ethylene Insensitive 2 (EIN2). Transformed plants showed phenotypic changes that were stably inherited over at least two generations. These changes were very similar to mutant phenotypes of the two genes in diploid model plants. Quantitative real-time polymerase chain reaction revealed a good correlation between decreasing mRNA levels and increasingly severe phenotypes. RNAi silencing had the same quantitative effect on all three homoeologous genes. The most severe phenotypes were observed in homozygous plants that showed the strongest mRNA reduction and, interestingly, produced around 2-fold the amount of small RNAs compared to heterozygous plants. This suggests that the effect of RNAi in hexaploid wheat is gene-dosage dependent. Wheat seedlings with low mRNA levels for EIN2 were ethylene insensitive. Thus, EIN2 is a positive regulator of the ethylene-signaling pathway in wheat, very similar to its homologs in Arabidopsis (Arabidopsis thaliana) and rice (Oryza sativa). Our data show that RNAi results in stably inherited phenotypes and therefore represents an efficient tool for functional genomic studies in polyploid wheat.