Application Of Jasmonic Acid Research Articles

Endoplasmic reticulum stress pathway mediates the early heat stress response of developing rice seeds.

A transient heat stress occurring during early seed development in rice (Oryza sativa) reduces seed size by altering endosperm development. However, the relationship between the timing of the stress and specific developmental stage on heat sensitivity is not well-understood. To address this, we imposed a series of non-overlapping heat stress treatments and found that young seeds are most sensitive during the first two days after flowering. Temporal transcriptome analysis of developing, heat stressed (35°C) seeds during this window shows that Inositol-requiring enzyme 1 (IRE1)-mediated endoplasmic reticulum (ER) stress response and jasmonic acid (JA) pathways are the early (1-3 h) drivers of heat stress response. We propose that increased JA levels under heat stress may precede ER stress response as JA application promotes the spliced form of OsbZIP50, an ER response marker gene linked to IRE1-specific pathway. This study presents temporal and mechanistic insights into the role of JA and ER stress signalling during early heat stress response of rice seeds that impact both grain size and quality. Modulating the heat sensitivity of the early sensing pathways and downstream endosperm development genes can enhance rice resilience to transient heat stress events.

Localized Induced Defenses Limit Gall Formation by Eriophyid Mite Against Invasive Lygodium microphyllum (Schizaeales: Lygodiaceae).

A potential barrier to the establishment of weed biological control agents is interference from other management tactics that induce plant defenses. Methods that suppress the weed such as feeding by other biological control agents or mechanical removal are especially disposed to inducing plant defenses and potentially limiting agent establishment. Here, we focused on the invasive weed Lygodium microphyllum (Cav.) R. Br. (Schizaeales: Lygodiaceae, Old World climbing fern) and one of its biological control agents, the mite Floracarus perrepae Knihinicki and Boczek (Acariformes: Eriophyidae). We experimentally induced plant defenses in potted plants via damage or application of jasmonic acid, a hormone typically involved in plant defenses, and measured the responses of the mite in a screenhouse. Localized damage to the pinnae (e.g., leaflets) via cutting or larval feeding from a second biological control agent, Neomusotima conspurcatalis (Warren) (Lepidoptera; Crambidae), reduced F. perrepae gall formation, but not the number of mites per gall. In contrast, damage to rachises (e.g., stems) did not affect galling, likely because plant defense responses were not systemic. Application of jasmonic acid reduced gall formation but not the numbers of mites within galls. Taken together, we found that localized damage interfered with gall formation but not within-gall reproduction. However, these effects on the mite from induced plant defenses are likely short-lived, and therefore interference between management tactics is unlikely to affect F. perrepae establishment and performance.

Changes in antioxidant enzymes activities and alkaloid amount of Catharanthus roseus in response to plant growth regulators under drought condition

Drought stress affects plant growth and is considered as one of the most important issues in In Middle East. In order to manage the critical water, it is essential to develop strategies to improve plant growth and biochemical characteristics. Plant growth regulators may afford a safe solution to increasing crop productivity via several mechanisms. Thus, the current study investigated the influence of salicylic acid and jasmonic acid on some physiological and antioxidant responses of Catharanthus roseus to drought stress under field conditions in Ahvaz and Tehran, Iran. The results indicated drought stress decreased total fresh and dry weights, relative water content, and concentration of photosynthetic pigments. In contrast, the activity of antioxidant enzymes and alkaloid contents would be increased. Foliar application of salicylic acid had a significant impact on all studied traits, but jasmonic acid had an effect only on total fresh and dry weights, concentration of photosynthetic pigments, and alkaloid contents. The activity of antioxidant enzymes including peroxidase, ascorbate peroxidase, superoxide dismutase, and polyphenol oxidase enhanced by spraying salicylic acid in deficit and good irrigation conditions. Foliar application of salicylic acid 10 mM on activity of antioxidant enzymes and salicylic acid 1 mM on relative water content and photosynthetic pigment content were more effective than other salicylic acid concentrations. Foliar application of jasmonic acid increased total fresh and dry weights also carotenoid content, but decreased total chlorophyll contents under stress conditions, in both places. Application of salicylic acid 0.1 mM + jasmonic acid increased total fresh and dry weights in any irrigation regimes, while this treatment increased carotenoid contents only under drought conditions in Ahvaz. Application of salicylic acid alone and with jasmonic acid significantly increased the alkaloid contents under severe drought stress. Salicylic acid improved C. roseus physiological performance and alkaloid contents, also it could be a way for periwinkle to alleviate the adverse effects of drought stress.

Interactive Effects of Mycorrhizae, Soil Phosphorus, and Light on Growth and Induction and Priming of Defense in Plantago lanceolata.

Increasing demands to reduce fertilizer and pesticide input in agriculture has triggered interest in arbuscular mycorrhizal fungi (AMF) that can enhance plant growth and confer mycorrhiza-induced resistance (MIR). MIR can be based on a variety of mechanisms, including induction of defense compounds, and sensitization of the plant’s immune system (priming) for enhanced defense against later arriving pests or pathogens signaled through jasmonic acid (JA). However, growth and resistance benefits of AMF highly depend on environmental conditions. Low soil P and non-limiting light conditions are expected to enhance MIR, as these conditions favor AMF colonization and because of observed positive cross-talk between the plant’s phosphate starvation response (PSR) and JA-dependent immunity. We therefore tested growth and resistance benefits of the AMF Funneliformis mosseae in Plantago lanceolata plants grown under different levels of soil P and light intensity. Resistance benefits were assessed in bioassays with the leaf chewing herbivore Mamestra brassicae. Half of the plants were induced by jasmonic acid prior to the bioassays to specifically test whether AMF primed plants for JA-signaled defense under different abiotic conditions. AMF reduced biomass production but contrary to prediction, this reduction was not strongest under conditions considered least optimal for carbon-for-nutrient trade (low light, high soil P). JA application induced resistance to M. brassicae, but its extent was independent of soil P and light conditions. Strikingly, in younger plants, JA-induced resistance was annulled by AMF under high resource conditions (high soil P, ample light), indicating that AMF did not prime but repressed JA-induced defense responses. In older plants, low soil P and light enhanced susceptibility to M. brassicae due to enhanced leaf nitrogen levels and reduced leaf levels of the defense metabolite catalpol. By contrast, in younger plants, low soil P enhanced resistance. Our results highlight that defense priming by AMF is not ubiquitous and calls for studies revealing the causes of the increasingly observed repression of JA-mediated defense by AMF. Our study further shows that in our system abiotic factors are significant modulators of defense responses, but more strongly so by directly modulating leaf quality than by modulating the effects of beneficial microbes on resistance.

OsJAZ9 is involved in water-deficit stress tolerance by regulating leaf width and stomatal density in rice

Drought stress poses a severe threat to grain yield in rice. Our previous report demonstrated the role of OsJAZ9 in potassium homeostasis by modulating Jasmonic Acid (JA) signalling. While both potassium (K) and JA are known to have an important role in drought stress response, JA's repressor, i.e., JAZs' role in drought stress, remains elusive. Here we report that OsJAZ9 plays a critical role in rice water-deficit stress tolerance via influencing JA and ABA signalling. Overexpression of OsJAZ9 led to the enhanced ABA and JA levels. Our data further revealed that exogenous JA application antagonises the ABA-mediated inhibition of seed germination. Further, OsJAZ9 overexpression reduces leaf width and stomata density, leading to lower leaf transpiration rates than WT. This reduced transpiration and higher K content as osmoticum improved the water-deficit stress tolerance in OsJAZ9 overexpression lines. On the contrary, OsJAZ9 RNAi lines displayed enhanced sensitivity towards water-deficit stress. Our data provide new insights on the role of JA signalling repressors in rice response to water-deficit stress.

Effect of soybean variety and systemic induction on herbivore feeding guilds

Plants are attacked by a variety of herbivores and respond with localized or systemic defenses. Plant defense against one feeding guild (e.g. chewing, piercing/sucking) may also affect alternate feeding guilds. To optimize host plant resistance, interactions between feeding guilds must be understood. Aphids are plant virus vectors whose vector efficiency can be altered by plant defenses. To determine if systemic induction influences aphid feeding behaviors related to virus transmission, three soybean varieties, Davis, Lyon, and Progeny 4906RR, were induced by subjecting plants to soybean looper (SBL) herbivory, or exogenous applications of either jasmonic acid (JA) or salicylic acid (SA). Green peach aphid (GPA) apterae feeding behavior was recorded on induced and control plants using the Electrical Penetration Graph (EPG) technique. SBL growth bioassays were used to assess systemic induction. Previous SBL herbivory reduced SBL larval weights when fed Progeny 4906RR. JA reduced larval weights on Progeny 4906RR and Davis. SA increased SBL larval weights on Lyon. SBL herbivory decreased behaviors associated with nonpersistent virus transmission in Davis and Progeny 4906RR. JA altered behaviors associated with virus transmission in Davis and increased behaviors associated with virus acquisition in Progeny 4906RR. SA delayed probing in Davis, but increased behaviors associated with virus transmission in Progeny 4906RR and Lyon. Inducing host plant resistance with JA may reduce herbivore performance and increase nonpersistent virus transmission. Previous chewing herbivory may decrease nonpersistent virus transmission by aphids but is variety dependent.

The influence of yeast extract and jasmonic acid on phenolic acids content of in vitro hairy root cultures of Orthosiphon aristatus

Phenolic acids represent a big group of plant secondary metabolites that can be used as food additives, nutraceuticals, and pharmaceuticals. Obtaining phenolic acids from the plant in vitro cultures provide an attractive alternative to produce high-value plant-derived products. The impact of yeast extract and jasmonic acid on the induction of defense responses and consequently the production of phenolic acids in vitro hairy root cultures of O. aristatus have been investigated. Treatment of O. aristatus cultures with jasmonic acid caused accumulation of 12.98 mg.g-1 DW of phenolic acids, elicitation with yeast extract resulted in the highest amount of phenolic acids, particularly in 17.99 mg.g-1 DW as compared to 4.03 mg.g-1 DW for the non-treated cultures. Individual phenolic acids showed a different response to elicitation. Particularly rosmarinic acid content on the control plot reached 2.89 mg.g-1 DW, while after the treatment with jasmonic acid is increased to 10.84 mg.g-1 DW and after yeast application, it was 14.31 mg.g-1 DW. Also, caffeic acid content increased until 0.75 and 2.01 mg.g-1 DW after application of jasmonic acid and yeast extract, while at the control plot its concentration was 0.58 mg.g-1 DW. Application of yeast extract influenced synthesis of phenolic acids in vitro cultures of O. aristatus stronger as jasmonic acid treatment.

Application of jasmonic acid at the stage of visible brown necrotic spots in Magnaporthe oryzae infection as a novel and environment-friendly control strategy for rice blast disease.

Rice blast disease is one of the most common rice diseases worldwide. It is essential to improve disease resistance through environment-friendly methods, while maintaining yield and quality parameters. In this study, jasmonic acid (JA), a plant hormone with anti-fungal activity, was obtained, at both low (100 μmol/L) and high (400 μmol/L) concentrations in rice leaves, before, during, and after infection, respectively. JA could inhibit germination and appressorium formation of rice blast spores in a dose-dependent manner. A total of 400-μmol/L JA treatment significantly enhanced cell viability and endogenous JA level in rice leaves. Furthermore, rice leaves inoculated with Magnaporthe oryzae and sprayed with JA 72 h post-inoculation showed the maximum symptom relief and the highest endogenous JA production among all treatment approaches. The expressions of defense-related genes, OsPR10a and OsAOS2, were highly up-regulated in response to JA, whereas OsEDS1 was down-regulated. Hence, we revealed that exogenous JA could activate JA signaling to effectively control the symptoms of rice blast.

Redox-Dependent Structural Modification of Nucleoredoxin Triggers Defense Responses against Alternaria brassicicola in Arabidopsis.

In plants, thioredoxin (TRX) family proteins participate in various biological processes by regulating the oxidative stress response. However, their role in phytohormone signaling remains largely unknown. In this study, we investigated the functions of TRX proteins in Arabidopsis thaliana. Quantitative polymerase chain reaction (qPCR) experiments revealed that the expression of ARABIDOPSIS NUCLEOREDOXIN 1 (AtNRX1) is specifically induced by the application of jasmonic acid (JA) and upon inoculation with a necrotrophic fungal pathogen, Alternaria brassicicola. The AtNRX1 protein usually exists as a low molecular weight (LMW) monomer and functions as a reductase, but under oxidative stress AtNRX1 transforms into polymeric forms. However, the AtNRX1M3 mutant protein, harboring four cysteine-to-serine substitutions in the TRX domain, did not show structural modification under oxidative stress. The Arabidopsis atnrx1 null mutant showed greater resistance to A. brassicicola than wild-type plants. In addition, plants overexpressing both AtNRX1 and AtNRX1M3 were susceptible to A. brassicicola infection. Together, these findings suggest that AtNRX1 normally suppresses the expression of defense-responsive genes, as if it were a safety pin, but functions as a molecular sensor through its redox-dependent structural modification to induce disease resistance in plants.

CmLOX10 positively regulates drought tolerance through jasmonic acid -mediated stomatal closure in oriental melon (Cucumis melo var. makuwa Makino)

Drought stress severely impairs plant growth and production. Lipoxygenase (LOX), a master regulator for lipid peroxidation, is critical for direct or indirect response to abiotic stresses. Here, we found that drought stress induced the transcription of CmLOX10 in leaves of oriental melon seedlings. Reverse genetic approaches and physiological analyses revealed that silencing CmLOX10 increased drought susceptibility and stomatal aperture in oriental melon seedlings, and that ectopic overexpression of CmLOX10 in Arabidopsis enhanced drought tolerance and decreased the stomatal aperture. Moreover, the transcription of jasmonic acid (JA)-related genes and JA accumulation were significantly induced in CmLOX10-overexpressed Arabidopsis, which were reversely suppressed in CmLOX10-silenced seedlings during the stage of drought stress. Foliar application of JA further verified that JA enhanced drought tolerance and induced stomatal closure in leaves of melon seedlings. In addition, the feedback regulation of CmLOX10 was induced by JA signaling, and the expression level of CmMYC2 was increased by JA and drought treatment. Yeast one-hybrid analysis showed that CmMYC2 directly bound to the promoter of CmLOX10. In summary, we identified the important roles of CmLOX10 in the regulation of drought tolerance in oriental melon seedlings through JA- mediated stomatal closure and JA signaling-mediated feedback through CmMYC2.

Wild strawberry shows genetic variation in tolerance but not resistance to a generalist herbivore.

Plants’ defenses against herbivores usually include both resistance and tolerance mechanisms. Their deployment has predominantly been studied in either single‐plant genotypes or multiple genotypes exposed to single herbivores. In natural situations, however, most plants are attacked by multiple herbivores. Therefore, aims of this study were to assess and compare the effects of single and multiple herbivores on plant resistance and tolerance traits, and the consequences for overall plant performance. For this, we exposed multiple genotypes of wild woodland strawberry (Fragaria vesca) to jasmonic acid (JA), to mimic chewing herbivory and induce the plants’ defense responses, and then introduced the generalist herbivore Spodoptera littoralis to feed on them. We found that woodland strawberry consistently showed resistance to S. littoralis herbivory, with no significant genetic variation between the genotypes. By contrast, the studied genotypes showed high variation in tolerance, suggesting evolutionary potential in this trait. Prior JA application did not alter these patterns, although it induced an even higher level of resistance in all tested genotypes. The study provides novel information that may be useful for breeders seeking to exploit tolerance and resistance mechanisms to improve strawberry crops’ viability and yields, particularly when multiple herbivores pose significant threats.

Seed priming and foliar application with jasmonic acid enhance salinity stress tolerance of soybean (Glycine max L.) seedlings.

Jasmonic acid (JA) is an important molecule that has a regulatory effect on many physiological processes in plant growth and development under abiotic stress. This study investigated the effect of 60 μmol L-1 of JA in seed priming (P) at 15 °C in darkness for 24 h, foliar application (F), and/or their combination effect (P + F) on two soybean cultivars - 'Nannong 99-6' (salt tolerant) and 'Lee 68' (salt sensitive) - under salinity stress (100 mmol L-1 sodium chloride (NaCl)). Salinity stress reduced seedling growth and biomass compared with that in the control condition. Priming and foliar application with JA and/or their combination significantly improved water potential, osmotic potential, water use efficiency, and relative water content of both cultivars under salinity stress. Similarly, seed priming with JA, foliar application of JA, and/or their combination significantly improved the following properties under salinity stress compared with the untreated seedlings: net photosynthetic rate by 68.03%, 59.85%, and 76.67% respectively; transpiration rate by 74.85%, 55.10%, and 80.26% respectively; stomatal conductance by 69.88%, 78.25%, and 26.24% respectively; intercellular carbon dioxide concentration by 61.64%, 40.06%, and 65.79% respectively; and total chlorophyll content by 47.41%, 41.02%, and 55.73% respectively. Soybean plants primed, sprayed with JA, or treated with their combination enhanced the chlorophyll fluorescence, which was damaged by salinity stress. JA treatments improved abscisic acid, gibberellic acid, and JA levels by 60.57%, 62.50% and 52.25% respectively under salt stress compared with those in the control condition. The transcriptional levels of the FeSOD, POD, CAT, and APX genes increased significantly in the NaCl-stressed seedlings irrespective of JA treatments. Moreover, JA treatment resulted in a reduction of sodium ion concentration and an increase of potassium ion concentrations in the leaf and root of both cultivars regardless of salinity stress. Monodehydroascorbate reductase, dehydroascorbate reductase, and proline contents decreased in the seedlings treated with JA under salinity stress, whereas the ascorbate content increased with JA treatment combined with NaCl stress. The application of 60 μmol L-1 JA improved plant growth by regulating the interaction between plant hormones and hydrogen peroxide, which may be involved in auxin signaling and stomatal closure under salt stress. These methods could efficiently protect early seedlings and alleviate salt stress damage and provide possibilities for use in improving soybean growth and inducing tolerance against excessive soil salinity. © 2020 Society of Chemical Industry.

Jasmonates induce growth and modulation in pigments and vitamins of Brassica oleracea var. capitata, italica and botrytis edible heads (foliage/inflorescence)

Jasmonates (JAs) are a rising class of lipid-derived signalling molecules with varied functions ranging from induction of abiotic and biotic stress-responsive genes to regulation of plant growth and development under natural condition. The rationale of present study was to investigate the nutritional importance of JAs in inducing and triggering accumulation of carbohydrates, sugars, nutritional pigments and vitamins in three varieties of Brassica oleracea L. (variety botrytis, capitata, italica) edible heads. Exogenous application of Jasmonic acid (JA) and methyl ester of Jasmonic acid (Me–JA), made edible heads of var. botrytis, capitata and italica nutritionally more accrete as compared to control untreated edible heads. Results showed that the treatment of JA and Me-JA enhanced growth of edible heads in terms of head diameter, head length, fresh weight, dry weight, moisture content, total protein, total starch, total carbohydrates, total soluble sugar, non-reducing sugar, vitamins C, A, E and B2 in var. botrytis but at the same time dramatic decline in reducing sugar, beta-carotene and lycopene was seen. In var. capitata certain reduction in vitamin E accumulation was recorded by the exogenous application of JA and Me–JA while overall growth of edible heads was accelerated which could also be supported by enhanced nutritional and productivity level. In variety italica, JAs reduced total starch and vitamin C, but overall growth was surged along with productivity. Both JA and Me-JA could be attributed to induce growth and enhance the nutritional potential of edible heads in three varieties of Brassica oleracea as compared to their untreated control edible heads. From the present results, it has been suggested that these two eco-friendly oxylipins can be further explored for enhancing the growth and nutritional value of these vegetables by exogenous application of JAs in μM to pM concentration.

Ectopic Expression of the Transcriptional Regulator silky3 Causes Pleiotropic Meristem and Sex Determination Defects in Maize Inflorescences.

Maize (Zea mays) is a monoecious plant, in which inflorescence morphogenesis involves complicated molecular regulatory mechanisms. Although many related genes have been cloned, our understanding of the molecular mechanism underlying maize inflorescence development remains limited. Here, we identified a maize semi-dominant mutant Silky3 (Si3), which displays pleiotropic defects during inflorescence development, including loss of determinacy and identity in meristems and floral organs, as well as the sexual transformation of tassel florets. We cloned the si3 gene using a map-based approach. Functional analysis reveals that SI3 is a nuclear protein and may act as a transcriptional regulator. Transcriptome analysis reveals that the ectopic expression of si3 strongly represses multiple biological processes, especially the flower development pathways. RNA in situ hybridization similarly shows that the expression patterns of genes responsible for flower development are changed in the Si3 mutant. In addition, the homeostasis of jasmonic acid and gibberellic acid are altered in the Si3 young tassels, and application of exogenous jasmonic acid can rescue the sex reversal phenotype of Si3 The defects we characterized in various regulatory pathways can explain the complex phenotypes of Si3 mutant, and this study deepens our knowledge of maize inflorescence development.

Effect of Exogenously Applied Jasmonic Acid and Kinetin on Drought Tolerance of Wheat Cultivars Based on Morpho-Physiological Evaluation

The population acceleration and better lifestyle submit new challenges for wheat researchers to breed wheat (Triticum sativum) cultivars with upgraded yield, quality, and resistance against abiotic stresses such as drought, so exploiting all available natural relatives of cultivated wheat and introducing even sensitive ones may be a useful approach to save time and efforts. Normally, the seedling stage is highly drought vulnerable, but for sensitive cultivars, the situation is more frustrating. We examine the potentiality of two regulating hormones in the upregulation of two wheat cultivars varying in their drought susceptibility at the seedling stage comparatively evaluated by morpho-physiological traits as indicators of drought tolerance. All the studied traits revealed cultivar-dependent variation in response to water deficit where cv. Sids 1 was tolerant and cv. Beni-suef 5 was sensitive. Shoot/root ratio, total water content, total dry weight, chlorophyll stability, total osmotic potential, osmoregulatory components, viz., soluble carbohydrates, soluble proteins and proline, membrane damage trait in terms of LOX, antioxidant defense system enzymatically in terms of APX, CAT, POD, SOD, and total antioxidant as drought tolerance indicators were the troubling shot due to water shortage in both cultivars. The damaging impacts of water deficit on these traits were conceived for sensitive cultivar compared with the tolerant one. Exogenous application of jasmonic acid (JA) or kinetin (K) efficiently conferred drought tolerance to sensitive cultivar to withstand harsh conditions in earlier stages and to perform comparably with tolerant ones. Applied hormones prompted unequivocal inversion from a state of downregulation to upregulation regarding all drought tolerance traits via reallocation of photoassimilates to vegetative sinks, thus promoting growth, increasing the accumulation of some osmoregulation compounds and thus increased tissue vigor and regulated the activity of antioxidant enzymes as well as morphological modulation attained by the restoration of shoot/root ratio. The results would promisingly be supportive of research programs seeking to develop anti-drought stress practices for sensitive wheat cultivars.

Growth, Physiological and Biochemical Traits of Sage under the Exogenous Stimulating and Stress Factors

Sage (Salvia officinalis L.) belonging to the Lamiaceae family, as the main herb in the world is cultivated in many countries for extraction of essential oil from the leaves. One of the most important uses of the plant is to use its leaves as raw material in pharmaceutical and cosmetics industries. Interaction effects of exogenous jasmonic acid (JA) at different concentrations (0.00, 400, and 600 µM) and the applied of arbuscular mycorrhizal fungi (AMF) in soil under different moisture conditions (control or non-stress, slightdrought, and mild drought stress) on growth, and morphophysiological characteristics of sage and the quantity and quality yield of essential oil from the sage leaves were investigated. The constituents in the essential oils from the sage leaves were analyzed by GC-FID and GC/MS. Results indicated that the inoculation with AMF meaningfully increased the growth parameters sage, while, the foliar spray of JA improved only physiological traits such as soluble sugar, proline, and anthocyanin in the leaves. Experimental treatments individually increased the concentrations of 1,8-cineole in the essential oils. The interaction effects including AMF × JA, AMF × irrigation, and JA × irrigation significantly affected the essential oil yield and the morphological characteristic of sage. The highest value of the essential oil yield was obtained from AMF-inoculation × mild drought × JA at 400 µM. Finally, the exogenous application of JA along inoculation with AMF changed some characteristics of the sage plant under drought stress condition. Indeed, AMF-inoculation and the foliar spraying of JA had synergistic effects on the amounts secondary metabolites of sage especially, 1,8-cineole. In conclusion, we found that the exogenous JA along the inoculation of arbuscular mycorrhizal improves growth characteristics and quality of the essential oil of sage and enhances water deficit tolerance.

Jasmonic acid and hydrogen sulfide modulate transcriptional and enzymatic changes of plasma membrane NADPH oxidases (NOXs) and decrease oxidative damage in Oryza sativa L. during thiocyanate exposure.

It is evident that the plasma membrane NADPH oxidases (NOXs) play an important role in the generation of superoxide radicals (O2-•) in plants during defense responses. This study was to clarify activation of NOXs in oxidative damage in Oryza sativa during SCN- exposure, particularly in the roles of jasmonic acid (JA) and hydrogen sulfide (H2S) on transcriptional and enzymatic changes of NOXs. Results indicated that enzymatic activity of NOXs in both roots and shoots was significantly enhanced during SCN- exposure, whereas the application of JA and H2S donor (NaHS) significantly repressed NOXs activity in SCN-treated rice seedlings. Similarly, ROS analysis showed that SCN- exposure elevated the content of O2-•, hydrogen peroxide (H2O2) and malondialdehyde (MDA) in rice tissues significantly, whereas decreases in O2-• and H2O2 were detected in roots and shoots of SCN-treated rice seedlings due to application of JA and NaHS. PCR analysis revealed different expression patterns of 7 plasma membrane-localized NOX genes in rice roots and shoots against SCN- exposure, suggesting that various isogenes of NOXs might regulate and determine activity of NOXs in rice organs. In conclusion, SCN- exposure was able to trigger activation of NOXs effectively, and led to oxidative damage and lipid peroxidation; the effects of JA and NaHS on inactivation of NOXs was evident and tissue specific, which in turn modulated ROS accumulation in rice plants.

Exogenous application of plant hormones in the field alters aboveground plant\u2013insect responses and belowground nutrient availability, but does not lead to differences in plant\u2013soil feedbacks

Plant–soil feedbacks of plants that are exposed to herbivory have been shown to differ from those of plants that are not exposed to herbivores. Likely, this process is mediated by jasmonic acid (JA) and salicylic acid (SA) defense pathways, which are induced by aboveground herbivory. Furthermore, exogenous application of these phytohormones to plants alters belowground communities, but whether this changes plant–soil feedbacks in natural systems is unknown. We applied exogenous sprays of JA and SA individually and in combination to field plots in a restored grassland. Control plots were sprayed with demineralized water. After three repeated application rounds, we transplanted seedlings of the plant–soil feedback model plant Jacobaea vulgaris as phytometer plants to test the effects of potential phytohormone-mediated changes in the soil, on plant performance during the response phase. We further measured how exogenous application of phytohormones altered plant-related ecosystem characteristics (plot-level); soil chemistry, plot productivity, insect communities and predation. Biomass of the phytometer plants only co-varied with plot productivity, but was not influenced by phytohormone applications. However, we did observe compound-specific effects of SA application on insect communities, most notably on parasitoid attraction, and of JA application on soil nitrogen levels. Although we did not find effects on plant–soil feedbacks, the effects of exogenous application of phytohormones did alter other ecosystem-level processes related to soil nutrient cycling, which may lead to legacy effects in the longer term. Furthermore, exogenous application of phytohormones led to altered attraction of specific insect groups.

Biochemical responses of water-stressed triticale (X Triticosecale wittmack) to humic acid and jasmonic acid

The efficacy of humic acid (HA) and jasmonic acid (JA) application to modulate the adverse effects of water stress on pigment content, relative water content (RWC), antioxidant enzyme activity, and ion balance of two triticale genotypes (ET-83-3 and ET-84-8) was investigated in a pot experiment under controlled conditions. Application of both HA and JA in ET-84-8, increased chlorophyll a and b content 19.9 and 21% under water stress, respectively. Carotenoid content was also increased from 7.7 mg/g fresh weight to 9.5 mg/g fresh weight under water stress. Furthermore, catalase (CAT) and peroxidase (POD) activities and proline content were increased 34.8%, 13% and 99.5%, respectively when ET-84-8 genotype was exposed to HA and JA together. RWC of water-stressed plants was lowered in both genotypes however, the decreasing rate was greater in ET-84-8genotype. Higher K‏+ accumulation in water-stressed ET-84-8 genotype was accompanied by an increase in pigment content, CAT and POD activity as well as RWC. There was a negatively significant relationship between the main shoot grain yield and the malondialdehyde (MDA) activity. Significant and positive relationships were also found between the main shoot grain yield with CAT activity as well as RWC. Overall, it was found that concomitant foliar application of HA (1.0 mM) with JA (50 µM) was able to alleviate the inhibitory effects of water stress in the ET-84-8 genotype via enhancing proline content, CAT and POD activity, and lowering MDA.

Use of plant-defense hormones against pathogen-diseases of postharvest fresh produce

The losses caused by pathogens on fresh products in postharvest can reach up to 50% of the harvest, which is why efficient strategies are required to increase the life of these products and reduce damage from diseases. In this sense, the use of plant-defense hormones represents an option that is respectful of health and the environment, as well as being effective, not only in reducing the incidence of diseases, but also in increasing the life of these fresh products. This work is an exhaustive compilation of the most recent studies carried out in the post-harvest biocontrol of pathogens through the exogenous application of the defense hormones jasmonic acid and salicylic acid in all the groups of perishable-plant products, pointing out the mechanisms involved.