Polysaccharide Elicitor Research Articles

Intricate intracellular kinase network regulates the Spodoptera lituta-derived elicitor response signaling in Arabidopsis.

Plants defend themselves against herbivores by recognizing herbivore-derived elicitors and activating intracellular signaling. In Arabidopsis, the receptor-like kinase HAK1 recognizes the poly-saccharide elicitor (FrA) from Spodoptera litura larvae, leading to the expression of defense-related genes such as PDF1.2. During this process, the cytoplasmic kinase CRK2 phosphorylates PBL27, triggers the ERF13 expression via ethylene signaling and subsequently leads to PDF1.2 expression. Herein, we investigated four cytoplasmic kinases from the same receptor-like cytoplasmic kinase (RLCK) VII family as PBL27 that interacts with CRK2. Among them, PBL11, like PBL27, is phosphorylated by CRK2 and induces PDF1.2 expression but does not affect ERF13 expression. The weight gain of S. litura larvae on PBL11-deficient mutant plants was only slightly higher than that of wild-type plants, suggesting that PBL11 may function as a minor RLCK that supports the defense response.

PCAP-1a, an exopolysaccharide from Pectobacterium actinidiae, exerts the dual role of immunogenicity and virulence in plants

Plant defense mechanisms begin with the recognition of microbe-associated molecular patterns or pathogen-associated molecular patterns (MAMPs/PAMPs). Several carbohydrates, such as chitin, were reported to induce plant defenses, acting as elicitors. Regrettably, the structures of polysaccharide elicitors have rarely been characterized, and their recognition receptors in plants remain unknown. In the present study, PCAP-1a, an exopolysaccharide (PCAP-1a) purified from Pectobacterium actinidiae, was characterized and found to induce rapid cell death of dicotyledons, acting as a polysaccharide elicitor to induce plant immunity. A series of pattern-triggered immunity (PTI) responses were triggered, including reactive oxygen species production, phosphorylation of mitogen-activated protein kinases and gene transcriptional reprogramming. Moreover, we confirmed that CERK1 is probably one of the immune coreceptors for plants to recognize PCAP-1a. Notably, PCAP-1a also promotes the infection caused by P. actinidiae. In conclusion, our study supports the potential of PCAP-1a as a toxin that plays a dual role of virulence and immune induction in pathogen-plant interactions.

Cytoplasmic Kinase Network Mediates Defense Response to Spodoptera litura in Arabidopsis.

Plants defend against folivores by responding to folivore-derived elicitors following activation of signaling cascade networks. In Arabidopsis, HAK1, a receptor-like kinase, responds to polysaccharide elicitors (Frα) that are present in oral secretions of Spodoptera litura larvae to upregulate defense genes (e.g., PDF1.2) mediated through downstream cytoplasmic kinase PBL27. Here, we explored whether other protein kinases, including CPKs and CRKs, function with PBL27 in the intracellular signaling network for anti-herbivore responses. We showed that CRK2 and CRK3 were found to interact with PBL27, but CPKs did not. Although transcripts of PDF1.2 were upregulated in leaves of wild-type Arabidopsis plants in response to mechanical damage with Frα, this failed in CRK2- and PBL27-deficient mutant plants, indicating that the CRK2/PBL27 system is predominantly responsible for the Frα-responsive transcription of PDF1.2 in S. litura-damaged plants. In addition to CRK2-phosphorylated ERF13, as shown previously, ethylene signaling in connection to CRK2-phosphorylated PBL27 was predicted to be responsible for transcriptional regulation of a gene for ethylene response factor 13 (ERF13). Taken together, these findings show that CRK2 regulates not only ERF13 phosphorylation but also PBL27-dependent de novo synthesis of ERF13, thus determining active defense traits against S. litura larvae via transcriptional regulation of PDF1.2.

Two polysaccharide elicitors trigger systemic acquired resistance to resist Sclerotium rolfsii and its transcriptional characteristic in Atractylodes macrocephala

The elicitors can trigger plants systemic acquired resistance. In contrast to the well-characterized exogenous elicitor-induced common response, little is known about how the plants have activated SAR response to pathogen challenge. Here, early transcriptional reprogramming and downstream immune outputs in SAR-activated plants against the Sclerotium rolfsii Sacc stress were investigated by comparative biochemical and transcriptomics in Atractylodes that sprayed by two polysaccharide elicitors (designated as CIP and SR). It was evident that the SAR-activated plants exhibit unique expression characteristics in response to pathogens stress, depending on the discrepancies between CIP and SR, the CIP-induced response depend on some antimicrobial proteins, but the SR depend on phytohormone genes family, in spite of both elicitors instigate common downstream immune output. Notably, some overlap genes not only occurred in SAR-activated plants but also in SAR-activated challenge plants, indicating invisible immune memory in plant. Otherwise, the SAR-activated plants share a reversed genes pattern with the SAR-activated challenge group, and they all tended to resist the susceptible plants' transcriptional reprogramming process (most positive defense genes were suppressed) via reversed genes pattern, which these up- and down-regulated in plant is analogous to “immuno-correct action” of animals’ vaccines.

Polysaccharide Elicitors Affect the Yield, Polysaccharide Synthase and Antibacterial Activity of Intracellular Polysaccharides from Submerged Culture of Cordyceps milifaris (Ascomycetes).

This study aimed to increase the yield of Cordyceps militaris intracellular polysaccharide (IPS) by adding elicitors. By comparing the effects of different elicitors on the IPS yield, three polysaccharide elicitors with significant promoting effect were screened out: Tween 80, pH, and vitamin B6 (VB6). We combined these elicitors and optimized the composition of the complex elicitor using response surface methodology to further improve the yield of IPS. The highest percentage of increased yield was 82.52 ± 0.48% obtained at a Tween concentration of 0.41% (w/v), pH of 4.98, and VB6 concentration of 0.17 mg/mL. Simultaneously, the mechanism of promoting high yield of IPS was preliminarily discussed. The complex elicitor may promote the synthesis of IPS by influencing the activity of polysaccharide synthase. Furthermore, the antibacterial activity against Staphylococcus aureus and Escherichia coli was evaluated. The addition of the complex elicitor increased the antibacterial activity of IPS. Therefore, our findings will lead the way for large scale industrial fermentations and commercial uses of IPS from C. militaris as antibacterial constituents.

Fungal endophytes from medicinal plant Bletilla striata (Thunb.) Reichb. F. promote the host plant growth and phenolic accumulation

Endophytic fungi are capable of increasing the growth and secondary metabolite production of medicinal plants in an ecofriendly and sustainable manner. Although these responses have been demonstrated in many plant species, they are not well understood in the medicinal plant Bletilla striata (Thunb.) Reichb.F.. Co-culture of B.striata with three endofungal isolates was carried out to evaluate the effects of endophytic fungal interaction on the plant growth and accumulation of phenols. The plant growth-promoting traits of isolated fungi were investigated, and the isolates had the ability to produce indole-3-acetic acid (IAA), siderophore and cellulolytic enzyme. The fungal strain Byssochlamys spectabilis 1-N2 co-cultured with plantlets of B. striata significantly increased certain growth properties, including shoot length by 71.40%, pseudobulbs dry weight by 52.58%, number of new roots by 5.25-fold, pseudobulbs diameter by 30.94% and improved the total phenolic content of the medicinal part by 25.41%. The fungal polysaccharide elicitor prepared from B.spectabilis 1-N2 mycelium also altered the accumulation of total phenolic content at different time points. Polysaccharide elicitor treatment significantly enhanced the accumulation of nitric oxide (NO) and salicylic acid (SA), which are involved in the plant defence response and significantly upregulated the activities of phenylalanine ammonia lyase (PAL), cinnamate-4-hydroxylase (C4H) and tyrosine ammonia lyase (TAL). The findings of this study contribute to our understanding of B. striata and endophytic fungi interactions and provide vital information for the use of endophytic fungi to improve plant growth and active component accumulation in B.striata cultivation.

Polysaccharide Elicitor from the Endophyte Bionectria sp. Fat6 Improves Growth of Tartary Buckwheat under Drought Stress

Drought can limit the growth and reduce the yield of crops, but the safe and effective bio-approach to improve the drought resistance of crops is very little. We conducted an experiment in which we monitored the effects of p... | Find, read and cite all the research you need on Tech Science Press

Endophytic Pseudomonas induces metabolic flux changes that enhance medicinal sesquiterpenoid accumulation in Atractylodes lancea

The bacterial endophyte Pseudomonas fluorescens ALEB7B significantly enhances photosynthate accumulations in Atractylodes lancea. These carbohydrates are preferentially used by the host plant to synthesize secondary metabolites, rather than to increase plant biomass accumulation. Mechanisms underlying the allocation of endophyte–increased carbohydrate in different plant metabolic processes are largely unknown. We have studied how P. fluorescens ALEB7B enhances photosynthate accumulation and how bacterial elicitors regulate metabolic flux and increase medicinal sesquiterpenoid formation in A. lancea using the sterile tissue culture plantlets. P. fluorescens ALEB7B enhances plant photosynthate accumulation by synthesizing and secreting indole–3–acetic acid, which has been demonstrated using high–performance liquid chromatography analysis. The increased endogenous indole–3–acetic acid promotes plant root development and then assimilation. Increased carbohydrates provide the material basis for the formations of terpenoid hydrocarbon scaffolds, which has been proved using gas chromatography analysis. Further, protein and polysaccharide elicitors secreted by P. fluorescens ALEB7B have been separated and purified from the bacterial fermentation broth, which have been applied to A. lancea plantlets. Both elicitors can stimulate the conversions of terpenoid hydrocarbon scaffolds to oxygenous sesquiterpenoids, the active medicinal ingredients in A. lancea, by triggering the oxidative burst in planta. Moreover, this study separates an ABC transporter substrate–binding protein from protein elicitors secreted by P. fluorescens ALEB7B with an ÄKTA Prime Plus Purifier System and firstly shows that this protein is essential to induce oxygenous sesquiterpenoid accumulation in A. lancea. This study provides new perspectives for mechanisms of medicinal oxygenous terpenoid synthesis, which has important reference values to the cultivation of medicinal plants that have terpenoids as their active ingredients, such as Artemisia annua and Taxus chinensis.

Effects of Polysaccharide Elicitors from Endophytic Fusarium oxysporum Fat9 on the Growth, Flavonoid Accumulation and Antioxidant Property of Fagopyrum tataricum Sprout Cultures.

The purpose of this study was to evaluate the effects of four different fungal polysaccharides, named water-extracted mycelia polysaccharide (WPS), sodium hydroxide-extracted mycelia polysaccharide (SPS), hydrochloric-extracted mycelia polysaccharide (APS), and exo-polysaccharide (EPS) obtained from the endophytic Fusarium oxysporum Fat9 on the sprout growth, flavonoid accumulation, and antioxidant capacity of tartary buckwheat. Without visible changes in the appearance of the sprouts, the exogenous polysaccharide elicitors strongly stimulated sprout growth and flavonoid production, and the stimulation effect was closely related with the polysaccharide (PS) species and its treatment dosage. With application of 200 mg/L of EPS, 200 mg/L of APS, 150 mg/L of WPS, or 100 mg/L of SPS, the total rutin and quercetin yields of buckwheat sprouts were significantly increased to 41.70 mg/(100 sprouts), 41.52 mg/(100 sprouts), 35.88 mg/(100 sprouts), and 32.95 mg/(100 sprouts), respectively. This was about 1.11 to 1.40-fold compared to the control culture of 31.40 mg/(100 sprouts). Moreover, the antioxidant capacity of tartary buckwheat sprouts was also enhanced after treatment with the four PS elicitors. Furthermore, the present study revealed the polysaccharide elicitation that caused the accumulation of functional flavonoid by stimulating the phenylpropanoid pathway. The application of beneficial fungal polysaccharide elicitors may be an effective approach to improve the nutritional and functional characteristics of tartary buckwheat sprouts.

Effects of polysaccharide elicitors from endophyticBionectria pityrodesFat6 on the growth and flavonoid production in tartary buckwheat sprout cultures

This study was to examine the effects of four fungal polysaccharides, namely exo-polysaccharide (EPS), water-extracted mycelia polysaccharide (WPS), sodium hydroxideextracted mycelia polysaccharide (SPS), and hydrochloric-extracted mycelia polysaccharide (APS) obtained from the endophytic fungus Bionectra pityrodes Fat6, on the sprout growth and flavonoids production of Fagopyrum tataricum. Without obvious changes in the appearance of the sprouts, the exogenous polysaccharide elicitors notably stimulated the sprout growth and functional metabolites accumulation, and the stimulation effect was mainly depended on the polysaccharide species along with its treatment dose. With application of 150 mg/l of EPS, 150 mg/l of WPS and 200 mg/l of SPS, the total rutin and quercetin yield of buckwheat sprouts was effectively increased to 49.18 mg/(100 sprouts), 50.54 mg/(100 sprouts), and 52.27 mg/(100 sprouts), respectively. That was about 1.57- to 1.66-fold in comparison with the control culture of 31.40 mg/(100 sprouts). Moreover, the present study revealed the accumulation of bioactive flavonoids resulted from the stimulation of the phenylpropanoid pathway by fungal polysaccharide treatments. It could be an efficient strategy for improving the nutritional and functional quality of tartary buckwheat sprouts applied with specific fungal elicitors.

Polysaccharide elicitors enhance phenylpropanoid and naphtodianthrone production in cell suspension cultures of Hypericum perforatum

Hypericum perforatum cell suspensions were evaluated for their growth, phenylpropanoid and naphtodianthrone productions, and antioxidant activity after treatments with polysaccharide elicitors chitin (CHI), pectin (PEC) and dextran (DEX). Polysaccharide elicitation of cell cultures showed a considerable improving effect on phenylpropanoid production (phenolics, flavonoids, flavanols and anthocyanins) during the post-elicitation period. Even that enhanced phenylpropanoid production was related to growth suppression of CHI elicited cells, PEC and DEX were presented as effective elicitors without loss of cell biomass. Phenylpropanoid accumulation in elicited cells was correlated to markedly higher enzyme activities of phenylalanine ammonia lyase and chalcone-flavanone isomerase. Cell cultures were found to respond rapidly towards the applied elicitors through an early stimulation of both naphtodiantrones, hypericin (HYP) and pseudohypericin (PHYP). The CHI was proposed as a much more prominent elicitor in stimulation of HYP and PHYP levels in cell suspensions. All tested polysaccharide elicitors stimulated non-enzymatic antioxidant properties in cell extracts indicating the potential role of phenolic compounds as effective antioxidants. With regards to the antioxidant enzymes, an up-regulation of peroxidase and catalase activities was observed in PEC and DEX elicited cells, whereas CHI did not give any stimulatory effect on enzymatic activities. These findings suggest the involvement of an efficient antioxidant defense system in the adaptive response of cells to polysaccharide elicitation. Altogether, these results indicated that H. perforatum cells elicited with polysaccharides represent a promising experimental system for enhanced production of phenylpropanoids and naphtodianthrones.

Efficient production of flavonoids in Fagopyrum tataricum hairy root cultures with yeast polysaccharide elicitation and medium renewal process.

Background:Tartary buckwheat (Fagopyrum tataricum), an excellent edible and medicinal crop, has been widely used as a daily diet and traditional medicine for a long time. The major functional components of Fagopyrum tataricum have been demonstrated to be flavonoids (i.e. rutin and quercetin), which had notable andioxidant, antidiabetic, hypocholesterolemic and antitumor activities. Hairy root culture is a convenient and efficient plant tissue culture system for large scale production of bioactive metabolites.Objective:To enhance the functional flavonoids production in hairy root culture of F. tataricum.Materials and Methods:The elicitation treatment in combination with medium renewal strategy was applied for efficient promoting flavonoids production in F. tataricum hairy root cultures.Results:The exogenous yeast polysaccharide (YPS) elicitor notably stimulated the functional metabolites production in F. tataricum hairy root cultures, and the stimulation effect was concentration-dependent. Combination with the YPS elicitation (200 mg/L) and medium renewal process, the maximal flavonoids yield was enhanced to 47.13 mg/L, about 3.2-fold in comparison with the control culture of 14.88 mg/L. Moreover, this research also revealed the accumulation of these bioactive metabolites resulted from the stimulation of the phenylpropanoid pathway by YPS treatment. These results indicated that the F. tataricum hairy root culture could be an effective system for rutin and quercetin production.

Effects of polysaccharide elicitors on secondary metabolite production and antioxidant response in Hypericum perforatum L. shoot cultures.

The effects of polysaccharide elicitors such as chitin, pectin, and dextran on the production of phenylpropanoids (phenolics and flavonoids) and naphtodianthrones (hypericin and pseudohypericin) in Hypericum perforatum shoot cultures were studied. Nonenzymatic antioxidant properties (NEAOP) and peroxidase (POD) activity were also observed in shoot extracts. The activities of phenylalanine ammonia lyase (PAL) and chalcone-flavanone isomerase (CHFI) were monitored to estimate channeling in phenylpropanoid/flavonoid pathways of elicited shoot cultures. A significant suppression of the production of total phenolics and flavonoids was observed in elicited shoots from day 14 to day 21 of postelicitation. This inhibition of phenylpropanoid production was probably due to the decrease in CHFI activity in elicited shoots. Pectin and dextran promoted accumulation of naphtodianthrones, particularly pseudohypericin, within 21 days of postelicitation. The enhanced accumulation of naphtodianthrones was positively correlated with an increase of PAL activity in elicited shoots. All tested elicitors induced NEAOP at day 7, while chitin and pectin showed increase in POD activity within the entire period of postelicitation. The POD activity was in significantly positive correlation with flavonoid and hypericin contents, suggesting a strong perturbation of the cell redox system and activation of defense responses in polysaccharide-elicited H. perforatum shoot cultures.

Polysaccharide elicitors enhance anthocyanin and phenolic acid accumulation in cell suspension cultures of Vitis vinifera

The effects of yeast extract and selected polysaccharide elicitors on secondary metabolite production, particularly of anthocyanin and phenolic acid, in cell suspension cultures of Vitis vinifera were investigated. All elicitors either maintained or promoted cell growth in culture. Overall, secondary metabolite production in V. vinifera cell suspension cultures responded differently to different elicitors. Chitosan, pectin, and alginate enhanced production of anthocyanin within 13 days of culture with levels of 2.5-, 2.5-, and 2.6-fold increase, respectively, over that of control. Chitosan, alginate, and gum arabic significantly promoted accumulation of phenolic acids, particularly 3-O-glucosyl-resveratrol, in V. vinifera cultures, as well as in the culture medium. Intracellular phenolic acid production was significantly enhanced by alginate and chitosan, with 1.7- and 1.5-fold levels, respectively, of that of control. Extracellular phenolic acid production was also significantly increased in the presence of chitosan and gum arabic, with levels of 3.3- and 1.7-fold higher, respectively, than those of control. In addition, DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging activity was enhanced in the presence of elicitors, and this was positively correlated with increased accumulation of anthocyanin in V. vinifera cell suspension cultures.

Carrageenan as an elicitor of induced secondary metabolites and its effects on various growth characters of chickpea and maize plants

The effects of polysaccharide elicitor k-carrageenan obtained from Hypnea musciformis, red algae on the production of Induced Secondary Metabolites, ISMs (the disease resistance compounds) and on various growth characters of chickpea and maize plants were studied. Experiments were conducted in the field of PCSIR Laboratories Complex Karachi during December 2008–April 2009 in randomized complete block design with three replications. Three elicitor treatments were used, a solid preparation in which the elicitor was mixed with soil (T2 1mg/g) and applied around the seeds in the soil. The two other preparations were liquid, T1 and T3 at a concentration of 100μgglceqml−1 and were applied around the sowing seeds and as a foliar spray on the plants, respectively. Statistical analysis of the data revealed that these treatments significantly enhanced all the growth characters of chickpea except T2 that gave the nonsignificant difference in the plant height. Maximum plant height (80.3cm), number of pods plant−1 (76.2), number of branches plant−1 (25.0), number of leaves plant−1 (125.6), earlier flowering and high ISMs contents in leaves, stem and grains of chickpea were recorded in T1 treated chickpea plants. In maize plants only T1 and T3 treatments (with minor exceptions) had significant effects on few characters like plant height, stem diameter, number of leaves plant−1 and on ISMs contents in leaves while number of cobs plant−1 and flowering time were nonsignificantly affected by these treatments. These results suggested that k-carrageenan elicitor can be used as a potent plant protectant as well as growth promoting agent especially for chickpea plants.

Significance of protein elicitor isolated from Tuber melanosporum on the production of ganoderic acid and Ganoderma polysaccharides during the fermentation of Ganoderma lucidum

Under the elicitation of protein elicitor isolated from the culture mycelia of Tuber melanosporum, the biosynthesis of ganoderic acids (GA) was significantly stimulated during Ganoderma lucidum fermentation. Compared with our previous results that, GA content was inhibited by polysaccharide elicitor isolated from T. melanosporum, while improved by the elicitor of polysaccharide and protein, protein was identified to be the exact component inducing GA biosynthesis in this work. G. lucidum cell growth was significantly inhibited by elicitor of polysaccharide and protein, and polysaccharide elicitor did not inhibit the cell growth. In this work, the remarkable inhibition on the cell growth was considerably eliminated under the elicitation of protein elicitor isolated from T. melanosporum. These suggested maybe the interaction of polysaccharide and protein components existed in the inhibition on the cell growth of G. lucidum. Not only GA content but also total GA accumulation obtained the highest values after the elicitation of protein elicitor. The maximal GA production of 260.5 ± 5.6 mg/L was 31.2% higher than the control. Under the elicitation of protein elicitor, the production of extracellular polysaccharide (EPS) and the content of intracellular polysaccharide (IPS) were also enhanced; however, total IPS accumulation was lower. GA biosynthesis was also significantly affected by the addition time of protein elicitor, whose optimal value was the culture of day 4.

Significance of fungal elicitors on the production of ganoderic acid and Ganoderma polysaccharides by the submerged culture of medicinal mushroom Ganoderma lucidum

The main components of polysaccharide, protein and lipid (i.e., whole elicitor) and the sole polysaccharide component (i.e., polysaccharide elicitor) isolated from the cultured mycelia of Tuber aestivum vittad significantly stimulated the accumulation of extracellular polysaccharides (EPS), and the highest EPS production of 0.92 ± 0.07 g/L was obtained by the elicitation of its whole elicitor. The highest content (i.e., 12.91 ± 1.05 mg/100 mg) and production (i.e., 1.94 ± 0.18 g/L) of intracellular polysaccharides (IPS) was obtained by adding the combination components of polysaccharide and protein (i.e., elicitor of polysaccharide and protein) from Tuber sinense. Specific ganoderic acid (GA) biosynthesis (i.e., GA content) was stimulated by adding the elicitor of polysaccharide and protein, while inhibited by the polysaccharide elicitor prepared from Tuber melanosporum. While, the maximal GA production of 315.5 ± 12.4 mg/L was obtained under the elicitation of polysaccharide elicitor from Penicillium citrinum because of a relatively high cell density.

The Signaling Role of Extracellular ATP and its Dependence on Ca2+ Flux in Elicitation of Salvia miltiorrhiza Hairy Root Cultures

The application of a polysaccharide elicitor from yeast extract, YE, to Salvia miltiorrhiza hairy root cultures induced transient release of ATP from the roots to the medium, leading to a dose-dependent increase in the extracellular ATP (eATP) level. The eATP level rose to a peak (about 6.5 nM with 100 mg l(-1) YE) at about 10 h after YE treatment, but dropped to the control level 6 h later. The elicitor-induced ATP release was dependent on membrane Ca2+ influx, and abolished by the Ca2+ chelator EGTA or the channel blocker La3+. The YE-induced H2O2 production was strongly inhibited by reactive blue (RB), a specific inhibitor of membrane purinoceptors. On the other hand, the application of exogenous ATP at 10-100 microM to the cultures also induced rapid and dose-dependent increases in H2O2 production and medium pH, both of which were effectively blocked by RB and EGTA. The non-hydrolyzable ATP analog ATPgammaS was as effective as ATP, but the hydrolyzed derivatives ADP or AMP were not so effective in inducing the pH and H2O2 increases. Our results suggest that ATP release is an early event and that eATP plays a signaling role in the elicitation of plant cell responses; Ca2+ is required for activation of the elicitor-induced ATP release and the eATP signal transduction. This is the first report on ATP release induced by a fungal elicitor and its involvement in the elicitor-induced responses in plant cells.

Differential regulation of MBP kinases by a glycoproptein elicitor and a polypeptide suppressor from Mycosphaerella pinodes in pea

A polypeptide fungal suppressor from a pea pathogen Mycosphaerella pinodes plays a key role in pathogenesis by suppressing elicitor-induced defense response(s) in pea ( Pisum sativum L). In this study, we show that treatment of pea tissues with the polysaccharide elicitor secreted by M. pinodes results in rapid increased activation of two myelin basic protein (MBP)-dependent kinases p44 (≈44 kDa) and p48 (≈48 kDa) within 15–30 min upon elicitation. Interestingly, the suppressor inhibited the elicitor-induced activation of only p44 kinase. While the defense-inducing signalling molecules, chitosan and salicylic acid (SA) activated the p44 and p48 kinases, methyl jasmonate (MeJA) did not. The abiotic stress signals, abscisic acid (ABA), NaCl and wounding activated the p48 kinase alone. These results demonstrate that MAPKs are differentially activated in response to pathogen invasion and abiotic stress in pea. Furthermore, specific inhibition of elicitor-induced p44 kinase activation by a MAPKK inhibitor, PD098059 and protein kinase inhibitor, K252a correlated with the suppression of elicitor-induced phenylalanine ammonia lyase (PAL) gene expression, supporting a role for p44 in the elicitor-induced defense response(s) in pea. Inhibition of p44 by the phosphoinositide (PI) turnover inhibitor, neomycin (a fungal suppressor mimic), and potentiation of p44 by the diacylglycerol (DAG) kinase inhibitor, R59022 indicated that p44 may be acting downstream of (PI) metabolism. Taken together, our results indicate that suppressor of defense elicitation from M. pinodes acts through inhibition of a MAPK (p44), possibly through a PI signaling pathway, facilitating the establishment of basic compatibility during infection of pea.

Effect of polysaccharide elicitors on the production of decursinol angelate inAgelica gigas Nakai root cultures

Root cultures ofAngelica gigas Nakai were found to be sensitive to elicitation by polysaccharide elicitors, such as methyl-β-cyclodextrin, glucan, carboxymethyl-β-chitin, chitosan, yeast extract and pectin. For the production of decursinol angelate, carboxymethyl-β-chitin and glucan were found to be the most efficient elicitors. The enhanced accumulation of decursinol angelate was proportional to the increase of the phenylalanine ammonia-lyase (PAL) activity after the treatment with most of the elicitors. However, carboxymethyl-β-chitin treatment did not stimulate the PAL activity, despite the 1.6-fold increase in the decursinol angelate production.