Involvement Of Salicylic Acid Research Articles

Involvement of salicylic acid against anthracnose disease in cassava

In this research, the involvement of salicylic acid (SA) as a plant growth regulator and a disease protector was investigated. SA at 9 concentrations was tested for their phytotoxicity, then 4 concentrations were selected for evaluating the effect of SA on root quantity and length as well as to study its inhibitory efficacy on mycelial growth and spore germination of Colletotrichum gloeosporioides, cassava anthracnose. The results showed that four low concentrations from 50–500 mg L−1 had no burns on leaf tissues. The SA at concentrations of 200 mg L−1 had high root number and length as well as effectively inhibited mycelial growth and spore germination of Colletotrichum. Subsequently, SA at 200 mg L−1 was tested under field conditions for two crop seasons. The plant height of SA treated-cassava was 178.36 ± 9.65 cm in the first crop season, and the height in the second crop season at 151.41 ± 5.55 cm, all effective when compared to the water control. For the anthracnose severity assessment, at 9 months old, plants treated with SA had lower disease severity.

Successful intergeneric transfer of a major apple scab resistance gene (Rvi6) from apple to pear and precise comparison of the downstream molecular mechanisms of this resistance in both species

BackgroundScab is the most important fungal disease of apple and pear. Apple (Malus x domestica Borkh.) and European pear (Pyrus communis L.) are genetically related but they are hosts of two different fungal species: Venturia inaequalis for apple and V. pyrina for European pear. The apple/V. inaequalis pathosystem is quite well known, whereas knowledge about the pear/V. pyrina pathosystem is still limited. The aim of our study was to analyse the mode of action of a major resistance gene of apple (Rvi6) in transgenic apple and pear plants interacting with the two scab species (V. inaequalis and V. pyrina), in order to determine the degree of functional transferability between the two pathosystems.ResultsTransgenic pear clones constitutively expressing the Rvi6 gene from apple were compared to a scab transgenic apple clone carrying the same construct. After inoculation in greenhouse with V. pyrina, strong defense reactions and very limited sporulation were observed on all transgenic pear clones tested. Microscopic observations revealed frequent aborted conidiophores in the Rvi6 transgenic pear / V. pyrina interaction. The macro- and microscopic observations were very comparable to the Rvi6 apple / V. inaequalis interaction. However, this resistance in pear proved variable according to the strain of V. pyrina, and one of the strains tested overcame the resistance of most of the transgenic pear clones. Comparative transcriptomic analyses of apple and pear resistant interactions with V. inaequalis and V. pyrina, respectively, revealed different cascades of molecular mechanisms downstream of the pathogen recognition by Rvi6 in the two species. Signal transduction was triggered in both species with calcium (and G-proteins in pear) and interconnected hormonal signaling (jasmonic acid in pear, auxins in apple and brassinosteroids in both species), without involvement of salicylic acid. This led to the induction of defense responses such as a remodeling of primary and secondary cell wall, lipids biosynthesis (galactolipids in apple and cutin and cuticular waxes in pear), systemic acquired resistance signal generation (in apple) or perception in distal tissues (in pear), and the biosynthesis of phenylpropanoids (flavonoids in apple but also lignin in pear).ConclusionThis study is the first example of a successful intergeneric transfer of a resistance gene among Rosaceae, with a resistance gene functioning towards another species of pathogen.

Transcriptional, hormonal, and metabolic changes in susceptible grape berries under powdery mildew infection.

Grapevine (Vitis vinifera) berries are extremely sensitive to infection by the biotrophic pathogen Erysiphe necator, causing powdery mildew disease with deleterious effects on grape and wine quality. The combined analysis of the transcriptome and metabolome associated with this common fungal infection has not been previously carried out in any fruit. In order to identify the molecular, hormonal, and metabolic mechanisms associated with infection, healthy and naturally infected V. vinifera cv. Carignan berries were collected at two developmental stages: late green (EL33) and early véraison (EL35). RNA sequencing combined with GC-electron impact ionization time-of-flight MS, GC-electron impact ionization/quadrupole MS, and LC-tandem MS analyses revealed that powdery mildew-susceptible grape berries were able to activate defensive mechanisms with the involvement of salicylic acid and jasmonates and to accumulate defense-associated metabolites (e.g. phenylpropanoids, fatty acids). The defensive strategies also indicated organ-specific responses, namely the activation of fatty acid biosynthesis. However, defense responses were not enough to restrict fungal growth. The fungal metabolic program during infection involves secretion of effectors related to effector-triggered susceptibility, carbohydrate-active enzymes and activation of sugar, fatty acid, and nitrogen uptake, and could be under epigenetic regulation. This study also identified potential metabolic biomarkers such as gallic, eicosanoic, and docosanoic acids and resveratrol, which can be used to monitor early stages of infection.

SA-Mediated Regulation and Control of Abiotic Stress Tolerance in Rice

Environmental or abiotic stresses are a common threat that remains a constant and common challenge to all plants. These threats whether singular or in combination can have devastating effects on plants. As a semiaquatic plant, rice succumbs to the same threats. Here we systematically look into the involvement of salicylic acid (SA) in the regulation of abiotic stress in rice. Studies have shown that the level of endogenous salicylic acid (SA) is high in rice compared to any other plant species. The reason behind this elevated level and the contribution of this molecule towards abiotic stress management and other underlying mechanisms remains poorly understood in rice. In this review we will address various abiotic stresses that affect the biochemistry and physiology of rice and the role played by SA in its regulation. Further, this review will elucidate the potential mechanisms that control SA-mediated stress tolerance in rice, leading to future prospects and direction for investigation.

Involvement of salicylic acid in the response to potassium deficiency revealed by metabolomics

Potassium (K) deficiency has consequences not only on cellular ion balance and transmembrane potential but also on metabolism. In fact, several enzymes are K-dependent including enzymes in catabolism, causing an alteration in glycolysis and respiration. In addition, K deficiency is associated with the induction of specific pathways and accumulation of metabolic biomarkers, such as putrescine. However, such drastic changes are usually observed when K deficiency is established. Here, we carried out a kinetic analysis with metabolomics to elucidate early metabolic events when nutrient conditions change from K-sufficiency to K-deficiency in Arabidopsis rosettes from both wild type and mutants affected in both K absorption and low-K signalling (hak5 akt1 cipk23). Our results show that mutants have a metabolomics pattern similar to K-deficient wild-type, showing a constitutive metabolic response to low K. In addition, shifting to low K conditions induces (i) changes in sugar metabolism and (ii) an accumulation of salicylic acid metabolites before the appearance of biomarkers of K deficiency (putrescine and aconitate), and such an accumulation is more pronounced in mutants. Our results suggest that early events in the response to low K conditions involve salicylic acid metabolism.

EFFECTS OF SALICYLIC ACID PRIMING FOR SALT STRESS TOLERANCE IN WHEAT

The present research experiment was conducted in the greenhouse of the Institute of Molecular Biology and Biotechnology, The University of Lahore for determining the possible involvement of salicylic acid (SA) in seed priming and affects on the seedling growth and development under NaCl treatments in wheat variety ANAJ-2017, Shafaq-2006 and Galaxy-2013. The data was collected for various seedling traits and statistically analyzed, which revealed the significance of results for treatments, salt applications, genotypes and the interactions between salt treatments and genotypes. The lower coefficient of variation was recorded for all studied traits which revealed that there was consistency among the results for salicylic acid applications and salt or NaCl treatments. It was concluded from our study that the application of salicylic acid (SA) under salt (NaCl) stress conditions helps wheat seedlings to withstand and compete with stressful conditions. The study revealed that the seed priming with salicylic acid helps to improve root length, shoot length, seedling moisture percentage and fresh seedling weights. The application of NaCl caused to increase the root length, number of roots and shoot length of wheat while salicylic acid (SA) was applied in foliar spray. The use of water priming shows medium effects for the seedling growth of wheat under salt stress environmental conditions. The wheat variety Galaxy-2013 has shown good performance for most of the studied traits of seedlings under salt stress conditions. It was suggested from our study that the variety Galaxy-2013 may be used under salt stress conditions or salt affected soils to improve grain yield of wheat.

Involvement of salicylic acid in cold priming-induced freezing tolerance in wheat plants

Freezing is one of the most damaging abiotic stress factors. Cold priming has been shown to enhance freezing tolerance in wheat. However, the underlying mechanisms are unclear. Salicylic acid (SA) is an important signal molecule involved in plant responses to abiotic and biotic stresses. This study aims to investigate the role of SA in cold priming-induced freezing tolerance in wheat plants. The results showed that the expression of gene encoding phenylalanine ammonia-lyase (PAL, a key enzyme involved in SA biosynthesis) and the level of endogenous SA (both free and conjugated) were significantly up-regulated following cold priming treatment. The role of SA in cold priming-induced freezing tolerance was further explored using the donor and inhibitor of endogenous SA. l-α-aminooxy-β-phenylpropionic acid (AOPP, a specific inhibitor of PAL) pretreatment reversed the increment of SA level induced by cold priming treatment, attenuated the positive effects of cold priming on antioxidant capacity (as indicated by the contents of MDA, ASA and GSH, and the activities of APX, GR, DHAR and MDHAR) and cold-responsive genes expression (such as AOX1a, IRI2 and HSP70) under the later freezing stress as well as the freezing tolerance (as indicated by the photochemical activity, electrolyte leakage and biomass). The application of exogenous SA could obviously counteract the negative effects of AOPP. Findings of the present study suggested that the roles of SA in cold priming-induced freezing tolerance in wheat might involve regulation of antioxidant capacity and cold-responsive gene expression.

Involvement of Salicylic Acid and Other Phenolic Compounds in Light-Dependent Cold Acclimation in Maize.

The exposure of plants to non-lethal low temperatures may increase their tolerance to a subsequent severe chilling stress. To some extent, this is also true for cold-sensitive species, including maize. In the present work, based on our previous microarray experiment, the differentially expressed genes with phenylpropanoid pathways in the focus were further investigated in relation to changes in certain phenolic compounds and other plant growth regulators. Phenylalanine ammonia lyase (PAL) was mainly activated under limited light conditions. However, light-induced anthocyanin accumulation occurred both in the leaves and roots. Chilling stress induced the accumulation of salicylic acid (SA), but this accumulation was moderated in the cold-acclimated plants. Acclimation also reduced the accumulation of jasmonic acid (JA) in the leaves, which was rather induced in the roots. The level of abscisic acid (ABA) is mainly related to the level of the stress, and less indicated the level of the acclimation. The highest glutathione (GSH) amount was observed during the recovery period in the leaves of plants that were cold acclimated at growth light, while their precursors started to accumulate GSH even during the chilling. In conclusion, different light conditions during the cold acclimation period differentially affected certain stress-related mechanisms in young maize plants and changes were also light-dependent in the root, not only in the leaves.

Involvement of Salicylic Acid in Anthracnose Infection in Tea Plants Revealed by Transcriptome Profiling.

Anthracnose is a major leaf disease in tea plant induced by Colletotrichum, which has led to substantial losses in yield and quality of tea. The molecular mechanism with regards to responses or resistance to anthracnose in tea remains unclear. A de novo transcriptome assembly dataset was generated from healthy and anthracnose-infected leaves on tea cultivars “Longjing-43” (LJ43) and “Zhenong-139” (ZN139), with 381.52 million pair-end reads, encompassing 47.78 billion bases. The unigenes were annotated versus Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), National Center for Biotechnology Information (NCBI) non-redundant protein sequences (Nr), evolutionary genealogy of genes: Non-supervised Orthologous Groups (eggNOG) and Swiss-prot. The number of differential expression genes (DEGs) detected between healthy and infected leaves was 1621 in LJ43 and 3089 in ZN139. The GO and KEGG enrichment analysis revealed that the DEGs were highly enriched in catalytic activity, oxidation-reduction, cell-wall reinforcement, plant hormone signal transduction and plant-pathogen interaction. Further studies by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) and high-performance liquid chromatography (HPLC) showed that expression of genes involved in endogenous salicylic acid biosynthesis and also accumulation of foliar salicylic acid are involved in the response of tea plant to anthracnose infection. This study firstly provided novel insight in salicylic acid acting as a key compound in the responses of tea plant to anthracnose disease. The transcriptome dataset in this study will facilitate to profile gene expression and metabolic networks associated with tea plant immunity against anthracnose.

Salicylic acid acts upstream of nitric oxide in elevated carbon dioxide-induced flavonoid biosynthesis in tea plant (Camellia sinensis L.)

Flavonoids are the most abundant polyphenols in tea (Camellia sinensis L.) with diverse medicinal values and stress adaptive roles. Flavonoid biosynthesis is largely influenced by environmental factors, including high atmospheric CO2. Although accumulation of certain flavonoids in tea leaves can be triggered by high CO2, the underlying mechanisms remain far from being substantiated. Despite the involvement of salicylic acid (SA) and nitric oxide (NO) in plant responses to biotic and abiotic stressors under high CO2, their roles in high CO2-induced plant secondary metabolism remain largely unknown, particularly in tea plants. This study revealed that the exposure of tea plants to high CO2 levels (550 and 800 μmol mol−1) rapidly increased the concentrations of flavonoid, SA and NO. Exogenous SA and sodium nitroprusside (a NO donor) increased flavonoid concentration only at ambient CO2 (400 μmol mol−1) but not at elevated CO2. Furthermore, suppression of endogenous SA by its biosynthesis inhibitor paclobutrazol and scavenging of NO by cPTIO (4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) reduced flavonoid concentration and phenylalanine ammonia-lyase activity under elevated CO2. While the scavenging of NO showed no effect on endogenous SA levels, SA deficiency attenuated elevated CO2-induced NO accumulation, suggesting that SA acts upstream of NO in elevated CO2-induced flavonoid biosynthesis. Notably, NO levels in SA-suppressed plants were several times greater than that of cPTIO-treated plants, indicating that SA-independent NO production might have a contribution to total NO accumulation under elevated CO2. This study unraveled the functional hierarchy and relationships of SA and NO in elevated CO2-induced flavonoid biosynthesis in tea leaves.

Involvement of salicylic acid, ethylene and jasmonic acid signalling pathways in the susceptibility of tomato to Fusarium oxysporum.

SummaryPhytohormones, such as salicylic acid (SA), ethylene (ET) and jasmonic acid (JA), play key roles in plant defence following pathogen attack. The involvement of these hormones in susceptibility following Fusarium oxysporum (Fo) infection has mostly been studied in Arabidopsis thaliana. However, Fo causes vascular wilt disease in a broad range of crops, including tomato (Solanum lycopersicum). Surprisingly little is known about the involvement of these phytohormones in the susceptibility of tomato towards Fo f. sp. lycopersici (Fol). Here, we investigate their involvement by the analysis of the expression of ET, JA and SA marker genes following Fol infection, and by bioassays of tomato mutants affected in either hormone production or perception. Fol inoculation triggered the expression of SA and ET marker genes, showing the activation of these pathways. NahG tomato, in which SA is degraded, became hypersusceptible to Fol infection and showed stronger disease symptoms than wild‐type. In contrast, ACD and Never ripe (Nr) mutants, in which ET biosynthesis and perception, respectively, are impaired, showed decreased disease symptoms and reduced fungal colonization on infection. The susceptibility of the def1 tomato mutant, and a prosystemin over‐expressing line, in which JA signalling is compromised or constitutively activated, respectively, was unaltered. Our results show that SA is a negative and ET a positive regulator of Fol susceptibility. The SA and ET signalling pathways appear to act synergistically, as an intact ET pathway is required for the induction of an SA marker gene, and vice versa.

Natural extracts from pepper, wild rue and clove can activate defenses against pathogens in tomato plants

Tomato is an important species grown in many countries, either in fields or greenhouses. Despite decades of improvement, it is still susceptible to diseases, thus requiring the use of chemical pesticides, especially in greenhouses. Nevertheless it is imperative to reduce the use of environmental-unfriendly phytochemicals and favor less toxic tools to fight pathogens. Plants possess elaborate mechanisms against diseases that can lead to resistance. In the present work, we investigate the induction of plant defenses by means of extracts from plants widespread and easy to find, also known for their antimicrobial properties. Aqueous extracts of pepper ‘Rocoto’, wild rue and ethanolic extracts of clove powder (whose inhibiting effect was assessed on Oidium sp. spores) were tested on tomato plants for their ability to induce expression of different defense genes (PRs and regulatory proteins) after spraying. As revealed by RT-qPCR, all extracts were able to induce mRNA accumulation of different PR and MAPK regulators for several hours upon treatment, with clove and wild rue being the strongest. This effect could also be reproduced in tomato plants after a second treatment, 15 days after the first. The same extracts were tested in tomato and tobacco plants via leaf infiltration, showing necrotic symptoms associated with the hypersensitive response, thus confirming the priming capacity of the extracts. The involvement of salicylic acid (SA) in these responses was verified by HPLC analysis and in SA-depleted transgenic tobacco (NahG). The results obtained suggest that natural antimicrobial extracts can be used to induce plant defenses and protect valuable crops. At the same time these low-cost extracts do not pose a threat to the environment or the farmer and can help reduce the farming costs, especially in developing countries.

The different interactions of Colletotrichum gloeosporioides with two strawberry varieties and the involvement of salicylic acid.

The disease symptoms recognized as ‘Anthracnose’ are caused by Colletotrichum spp. and lead to large-scale strawberry (Fragaria×ananassa Duchesne) losses worldwide in terms of both quality and production. Little is known regarding the mechanisms underlying the genetic variations in the strawberry–Colletotrichum spp. interaction. In this work, Colletotrichum gloeosporioides (C. gloeosporioides) infection was characterized in two varieties exhibiting different susceptibilities, and the involvement of salicylic acid (SA) was examined. Light microscopic observation showed that C. gloeosporioides conidia germinated earlier and faster on the leaf surface of the susceptible cultivar compared with the less-susceptible cultivar. Several PR genes were differentially expressed, with higher-amplitude changes observed in the less-susceptible cultivar. The less-susceptible cultivar contained a higher level of basal SA, and the SA levels increased rapidly upon infection, followed by a sharp decrease before the necrotrophic phase. External SA pretreatment reduced susceptibility and elevated the internal SA levels in both varieties, which were sharply reduced in the susceptible cultivar upon inoculation. The less-susceptible cultivar also displayed a more sensitive and marked increase in the transcripts of NB-LRR genes to C. gloeosporioides, and SA pretreatment differentially induced transcript accumulation in the two varieties during infection. Furthermore, SA directly inhibited the germination of C. gloeosporioides conidia; NB-LRR transcript accumulation in response to SA pretreatment was both dose- and cultivar-dependent. The results demonstrate that the less-susceptible cultivar showed reduced conidia germination. The contribution of SA might involve microbial isolate-specific sensitivity to SA, cultivar/tissue-specific SA homeostasis and signaling, and the sensitivity of R genes and the related defense network to SA and pathogens.

The possible involvement of salicylic acid and hydrogen peroxide in the systemic promotion of phenolic biosynthesis in clover roots colonized by arbuscular mycorrhizal fungus

Arbuscular mycorrhizal fungal (AMF) colonization can induce both the local and the systemic increase in phenolic accumulation in hosts. However, the signaling molecules responsible for the systemic induction is still unclear. In this study, a split-root rhizobox system was designed to explore these molecules, with one half of clover (Trifolium repense) roots colonized by AMF, Funneliformis mosseae (formerly known as Glomus mosseae), and the other not (NM/M). Plants with two halves both (M/M) or neither (NM/NM) inoculated were also established for comparison. The contents of phenols and the accumulation of salicylic acid (SA), hydrogen peroxide (H2O2) and nitric oxide (NO) in roots were monitored, the activities of l-phenylalanine ammonia-lyase (PAL) and nitric oxide synthase (NOS) in roots were assayed, and the expressions of pal and chs (gene encoding chalcone synthase) genes in roots were also quantified using qRT-PCR. Results indicated that when phenolic content in NM/NM plants was lower than that in M/M plants, AMF colonization systemically induced the increase in phenolic content in NM/M plants. Similarly, the accumulations of SA and H2O2 were increased by AMF both locally and systemically, while that of NO was only increased locally. Moreover, enzyme assay and qRT-PCR were in accordance with these results. These data suggest that AMF colonization can systemically increase the phenolic biosynthesis, and SA and H2O2 are possibly the signaling molecules involved. The role of MeSA, a signaling molecule capable of long distance transport in this process, is also discussed.

Stress enhances the gene expression and enzyme activity of phenylalanine ammonia-lyase and the endogenous content of salicylic acid to induce flowering in pharbitis

The involvement of salicylic acid (SA) in the regulation of stress-induced flowering in the short-day plant pharbitis (also called Japanese morning glory) Ipomoea nil (formerly Pharbitis nil) was studied. Pharbitis cv. Violet was induced to flower when grown in 1/100-strength mineral nutrient solution under non-inductive long-day conditions. All fully expanded true leaves were removed from seedlings, leaving only the cotyledons, and flowering was induced under poor-nutrition stress conditions. This indicates that cotyledons can play a role in the regulation of poor-nutrition stress-induced flowering. The expression of the pharbitis homolog of PHENYLALANINE AMMONIA-LYASE, the enzyme activity of phenylalanine ammonia-lyase (PAL; E.C. 4.3.1.5) and the content of SA in the cotyledons were all up-regulated by the stress treatment. The Violet was also induced to flower by low-temperature stress, DNA demethylation and short-day treatment. Low-temperature stress enhanced PAL activity, whereas non-stress factors such as DNA demethylation and short-day treatment decreased the activity. The PAL enzyme activity was also examined in another cultivar, Tendan, obtaining similar results to Violet. The exogenously applied SA did not induce flowering under non-stress conditions but did promote flowering under weak stress conditions in both cultivars. These results suggest that stress-induced flowering in pharbitis is induced, at least partly, by SA, and the synthesis of SA is promoted by PAL.

Involvement of Salicylic Acid in Sulfur Induced Salinity Tolerance: A Role of Glutathione

Plants are severely affected by salinity due to its high magnitude of adverse impacts and worldwide distribution. Among various strategies, nutrient management may be an important aspect in alleviating stress under varied environmental conditions. The uptake and assimilation of sulfur plays an inevitable and imperative role in determining plant growth and development and is a fundamental part of several important compounds, such as glutathione, co-enzymes, vitamins, phytohormones and reduced sulfur compounds that decipher growth and vigour of plants under optimal and stressful environments. Assimilatory sulfate reduction may induce salt tolerance by coordinating various physiological processes and molecular mechanisms which are likely to be induced b y phytohormones. Among phytohormones salicylic acid (SA) could provide tolerance against salinity stress by enhancing physiological processes and can improve salinity tolerance by its effect on sulfur assimilation pathway as biochemically or molecular mechanisms. The present review critically evaluates the recent studies on the modulation of sulfur assimilation and gives an insight into the role of glutathione to maintain redox state and their cumulative significance in plants’ tolerance to salinity by SA in inducing various physiological responses in plants under salinity stress.

Involvement of salicylic acid, glutathione and protein S-thiolation in plant cell death-mediated defence response of Mesembryanthemum crystallinum against Botrytis cinerea

The response of Mesembryanthemum crystallinum plants performing C3 photosynthesis and crassulacean acid metabolism (CAM) to the non-host necrotrophic pathogen Botrytis cinerea was analyzed at the local and systemic levels. The induction of programmed cell death, lignin and callose deposition, changes in salicylic acid, glutathione and cysteinylglycine pools as well as the content of thiolated proteins were studied. The infected C3 and CAM plants exhibited hypersensitive-like defence response, however fluorescence staining with acridine orange and ethidium bromide revealed programmed cell death events in C3 plants only. The local immune response was not related to callose and lignin deposition. In the infected plants, salicylic acid, glutathione and cysteinylglycine, the first product of glutathione catabolism, as well as protein S-thiolation, predominantly S-glutathionylation, contributed to local defence at sites of inoculation. They (except protein thiolation) were also active in the establishment of systemic acclimation response monitored in the non-treated upper leaves. The extent to which they were involved in the local and systemic responses induced by B. cinerea differed in C3 and CAM plants. The accumulation of free salicylic acid, both in treated and upper leaves of the infected plants, was much more pronounced in CAM plants. The results have been discussed with respect to redox regulations in defence against necrotrophic pathogens and to stress acclimation.

Involvement of salicylic acid on antioxidant and anticancer properties, anthocyanin production and chalcone synthase activity in ginger (Zingiber officinale Roscoe) varieties.

The effect of foliar application of salicylic acid (SA) at different concentrations (10−3 M and 10−5 M) was investigated on the production of secondary metabolites (flavonoids), chalcone synthase (CHS) activity, antioxidant activity and anticancer activity (against breast cancer cell lines MCF-7 and MDA-MB-231) in two varieties of Malaysian ginger, namely Halia Bentong and Halia Bara. The results of high performance liquid chromatography (HPLC) analysis showed that application of SA induced the synthesis of anthocyanin and fisetin in both varieties. Anthocyanin and fisetin were not detected in the control plants. Accordingly, the concentrations of some flavonoids (rutin and apigenin) decreased significantly in plants treated with different concentrations of SA. The present study showed that SA enhanced the chalcone synthase (CHS) enzyme activity (involving flavonoid synthesis) and recorded the highest activity value of 5.77 nkat /mg protein in Halia Bara with the 10−5 M SA treatment. As the SA concentration was decreased from 10−3 M to 10−5 M, the free radical scavenging power (FRAP) increased about 23% in Halia Bentong and 10.6% in Halia Bara. At a concentration of 350 μg mL−1, the DPPH antioxidant activity recorded the highest value of 58.30%–72.90% with the 10−5 M SA treatment followed by the 10−3 M SA (52.14%–63.66%) treatment. The lowest value was recorded in the untreated control plants (42.5%–46.7%). These results indicate that SA can act not only as an inducer but also as an inhibitor of secondary metabolites. Meanwhile, the highest anticancer activity against MCF-7 and MDA-MB-231 cell lines was observed for H. Bara extracts treated with 10−5 M SA with values of 61.53 and 59.88%, respectively. The results suggest that the high anticancer activity in these varieties may be related to the high concentration of potent anticancer components including fisetin and anthocyanin. The results thus indicate that the synthesis of flavonoids in ginger can be increased by foliar application of SA in a controlled environment and that the anticancer activity in young ginger extracts could be improved.

Naringenin inhibits seed germination and seedling root growth through a salicylic acid-independent mechanism in Arabidopsis thaliana

Flavonoids fulfill an enormous range of biological functions in plants. In seeds, these compounds play several roles; for instance proanthocyanidins protect them from moisture, pathogen attacks, mechanical stress, UV radiation, etc., and flavonols have been suggested to protect the embryo from oxidative stress. The present study aimed at determining the role of flavonoids in Arabidopsis thaliana (L.) seed germination, and the involvement of salicylic acid (SA) and auxin (indole-3-acetic acid), two phytohormones with the same biosynthetic origin as flavonoids, the shikimate pathway, in such a putative role. We show that naringenin, a flavanone, strongly inhibits the germination of A. thaliana seeds in a dose-dependent and SA-independent manner. Altered auxin levels do not affect seed germination in Arabidopsis, but impaired auxin transport does, although to a minor extent. Naringenin and N-1-naphthylphthalamic acid (NPA) impair auxin transport through the same mechanisms, so the inhibition of germination by naringenin might involve impaired auxin transport among other mechanisms. From the present study it is concluded that naringenin inhibits the germination of Arabidopsis seeds in a dose-dependent and SA-independent manner, and the results also suggest that such effects are exerted, at least to some extent, through impaired auxin transport, although additional mechanisms seem to operate as well.

Shade light interaction with salicylic acid in regulating growth of sun (alpine) and shade (prairie) ecotypes of Stellaria longipes

The possible involvement of salicylic acid (SA) in a typical growth response of plants to shade light was investigated using the model system Stellaria longipes L. Goldie. The prairie (shade) ecotype of S. longipes is from foothills grassland habitat where it grows under shrubs or among taller grasses. The plants of this ecotype responded, as expected, with increased growth under lower red to far-red (R/FR) ratio and reduced photosynthetically active radiation (PAR). By contrast, the alpine (sun) ecotype is from an open sunny habitat, where canopy shade is a non-factor. The plants of this ecotype failed to respond with increased growth under a lower R/FR ratio, but had increased growth under a reduced PAR level. To examine the possible role of SA in shade light-mediated growth, the two main components of shade light, R/FR ratio and PAR, were uncoupled, and a series of experiments were performed by measuring the endogenous SA content and the plant response to exogenous SA concentrations. Contrary to the alpine plants, the prairie plants had increased endogenous SA content and higher shoot biomass accumulation under a low R/FR ratio treatment compared with normal or high R/FR ratios. Both alpine and prairie plants responded to a low PAR treatment with a decrease in endogenous SA content and an increase in shoot biomass accumulation, but the magnitude of this response was higher in prairie plants. Based on the results of this study, we conclude that shoot SA content is differentially regulated by both R/FR ratio and PAR signals, and SA may contribute, in ecotype specific manner, to growth changes in plants subjected to changing light environments.