Differential elicitation of proteases and protease inhibitors in two different genotypes of chickpea (Cicer arietinum) by salicylic acid and spermine

The impact of spring wheat species and sowing density on soil biochemical properties, content of secondary plant metabolites and the presence of Oulema ssp

The physical and chemical properties of the soil are important factors influencing the yield of crops. One of the agrotechnical factors influencing the biochemical properties of soil is sowing density. It affects the yield components, light, moisture and thermal conditions in the canopy and the pressure of pests. Secondary metabolites, many of which are known to act as a defense mechanism against insects, are of importance in the interaction between the crop and abiotic and biotic factors of the habitat. To the best of our knowledge, the studies conducted so far do not sufficiently reveal the impacts of the wheat species and the sowing density, together with the biochemical properties of the soil, on the accumulation of bioactive ingredients in the crop plants, and the subsequent impacts on the occurrence of phytophagic entomofauna in various management systems. Explaining these processes creates an opportunity for more sustainable development of agriculture. The study aimed to determine the effect of wheat species and sowing density on the biochemical properties of the soil, concentrations of biologically active compounds in the plant and the occurrence of insect pests in organic (OPS) and conventional (CPS) production systems. The research was conducted on spring wheat species (Indian dwarf wheat-Triticum sphaerococcum Percival and Persian wheat-Triticum persicum Vavilov) grown in OPS and CPS at sowing densities 400, 500, 600 (seeds m^-2). The following analyzes were performed: (i) soil analysis: the activity of catalases (CAT), dehydrogenases (DEH), peroxidases (PER); (ii) plant analysis: total phenolic compounds (TP), chlorogenic acid (CA), antioxidant capacity (FRAP); (iii) entomological analysis of the number of insects-Oulema spp. adults and larvae. Performing analyzes in such a wide (interdisciplinary) scope will allow for a comprehensive understanding of the soil-plant-insect biological transformation evaluation. Our results showed that an increase in soil enzyme activity caused a decrease in TP contents in the wheat grown the OPS. Despite this, both the content of TP and the anti-oxidative activity of the ferric reducing ability of plasma (FRAP) were higher in these wheats. Bioactive compound contents and FRAP were most favoured by the lowest sowing density. Regardless of the production system, the occurrence of the Oulema spp. adults on T. sphaerococcum was the lowest at a sowing density of 500 seeds m^-2. The occurrence of this pest's larvae was lowest at a sowing density of 400 seeds m^-2. Research on bioactive compounds in plants, biochemical properties of soil and the occurrence of pests make it possible to comprehensively assess the impact of the sowing density of ancient wheat in the ecological and conventional production system, which is necessary for the development of environmentally sustainable agriculture.

Interaction between polyamines and ethylene in the response to salicylic acid under normal photoperiod and prolonged darkness

The impact of salicylic acid (SA) on ethylene (ET) production and polyamine (PA) metabolism was investigated in wild type (WT) and ET receptor mutant Never ripe (Nr) tomato leaves under normal photoperiod and prolonged darkness. Nr displayed higher ET emanation compared to WT under control conditions and after SA treatments, but the ET signalling was blocked in these tissues. The accumulation of PAs was induced by 1 mM but not by 0.1 mM SA and was higher in WT than in Nr leaves. Upon 1 mM SA treatment, which caused hypersensitive response, illuminated leaves of WT showed high spermine (Spm) content in parallel with an increased expression of S-adenosylmethionine decarboxylase and Spm synthase (SlSPMS) suggesting that this process depended on the light. In Nr, however, Spm content and the expression of the SlSPMS gene were very low independently of the light conditions and SA treatments. This suggests that Spm synthesis needs functional ET perception. In WT leaves 1 mM SA enhanced putrescine (Put) synthesis by increasing the expression of Put biosynthesis genes, arginine and ornithine decarboxylases under darkness, while they were down-regulated in Nr. The activities of diamine (DAO) and polyamine oxidases (PAO), however, were generally higher in Nr compared to the WT after SA treatments. In Nr both SA applications increased the expression of SlPAO1 under normal photoperiod, while SlPAO2 was down-regulated in the dark suggesting a diverse role of PAOs in PA catabolism. These results indicated that ET could modulate the SA-induced PA metabolism in light-dependent manner.

Spermine Is a Potent Plant Defense Activator Against Gray Mold Disease on Solanum lycopersicum, Phaseolus vulgaris, and Arabidopsis thaliana

Polyamines (PAs) are ubiquitous aliphatic amines that play important roles in growth, development, and environmental stress responses in plants. In this study, we report that exogenous application of spermine (Spm) is effective in the induction of resistance to gray mold disease, which is caused by the necrotrophic fungal pathogen Botrytis cinerea, on tomato (Solanum lycopersicum), bean (Phaseolus vulgaris), and Arabidopsis thaliana. High throughput transcriptome analysis revealed a priming role for the Spm molecule in the genus Arabidopsis, resulting in strong upregulation of several important defense-associated genes, particularly those involved in systemic-acquired resistance. Microscopic analysis confirmed that Spm application potentiates endogenous defense responses in tomato leaves through the generation of reactive oxygen species and the hypersensitive response, which effectively contained B. cinerea growth within the inoculated area. Moreover, co-application of Spm and salicylic acid resulted in a synergistic effect against the pathogen, leading to higher levels of resistance than those induced by separate applications of the two compounds. The Spm plus salicylic acid treatment also reduced infection in systemic nontreated leaves of tomato plants. Our findings suggest that Spm, particularly when applied in combination with salicylic acid, functions as a potent plant defense activator that leads to effective local and systemic resistance against B. cinerea.

Herbivory and relative growth rates of Pieris rapae are correlated with host constitutive salicylic acid and flowering time

Treatment of plants with exogenous salicylic acid (SA) improves resistance to many bacterial pathogens, but can suppress resistance to insect herbivores. While plants vary naturally in constitutive SA, whether such differences are predictive of resistance to insect herbivores has not been studied previously. We examined the possible role of this endogenous SA in structuring the interactions between the cabbage white butterfly, Pieris rapae, and ten hosts in the mustard family (Brassicaceae). Because P. rapae has multiple generations that utilize different hosts across the year, we included five spring-flowering mustards and five summer-flowering mustards that co-occur in ruderal habitats in upstate New York. Under common garden conditions, the spring flowering mustards (Capsella bursa-pastoris, Draba verna, Cardamine impatiens, Barbarea vulgaris, and Arabidopsis thaliana) were significantly more resistant to P. rapae, supporting 42 % less herbivory (P = 0.015) and 64 % lower relative growth rates (P = 0.007), relative to the summer flowering mustards (Sisymbrium altissimum, Brassica nigra, Sinapis arvense, Lepidium campestre, and Arabis canadensis). Leaf total constitutive SA explained significant variation in larval herbivory (R² = 75.3 %, P = 0.007) and relative growth rates (R² = 59.4 %, P = 0.043). The three species with the lowest levels of constitutive SA (Capsella bursa-pastoris, Draba verna, and Cardamine impatiens) were the most resistant to larvae. Barbarea vulgaris and Arabis canadensis were notable exceptions, exhibiting high SA concentrations and intermediate resistance to P. rapae. These results suggest a curvilinear relationship between leaf constitutive SA and the herbivory by P. rapae, and they provide some insight into the ecology and possible management of this economically important crop pest.

Interactions between the jasmonic and salicylic acid pathway modulate the plant metabolome and affect herbivores of different feeding types

The phytohormones jasmonic acid (JA) and salicylic acid (SA) mediate induced plant defences and the corresponding pathways interact in a complex manner as has been shown on the transcript and proteine level. Downstream, metabolic changes are important for plant-herbivore interactions. This study investigated metabolic changes in leaf tissue and phloem exudates of Plantago lanceolata after single and combined JA and SA applications as well as consequences on chewing-biting (Heliothis virescens) and piercing-sucking (Myzus persicae) herbivores. Targeted metabolite profiling and untargeted metabolic fingerprinting uncovered different categories of plant metabolites, which were influenced in a specific manner, indicating points of divergence, convergence, positive crosstalk and pronounced mutual antagonism between the signaling pathways. Phytohormone-specific decreases of primary metabolite pool sizes in the phloem exudates may indicate shifts in sink-source relations, resource allocation, nutrient uptake or photosynthesis. Survival of both herbivore species was significantly reduced by JA and SA treatments. However, the combined application of JA and SA attenuated the negative effects at least against H. virescens suggesting that mutual antagonism between the JA and SA pathway may be responsible. Pathway interactions provide a great regulatory potential for the plant that allows triggering of appropriate defences when attacked by different antagonist species.

Physiological and molecular implications of plant polyamine metabolism during biotic interactions

During ontogeny, plants interact with a wide variety of microorganisms. The association with mutualistic microbes results in benefits for the plant. By contrast, pathogens may cause a remarkable impairment of plant growth and development. Both types of plant-microbe interactions provoke notable changes in the polyamine (PA) metabolism of the host and/or the microbe, being each interaction a complex and dynamic process. It has been well documented that the levels of free and conjugated PAs undergo profound changes in plant tissues during the interaction with microorganisms. In general, this is correlated with a precise and coordinated regulation of PA biosynthetic and catabolic enzymes. Interestingly, some evidence suggests that the relative importance of these metabolic pathways may depend on the nature of the microorganism, a concept that stems from the fact that these amines mediate the activation of plant defense mechanisms. This effect is mediated mostly through PA oxidation, even though part of the response is activated by non-oxidized PAs. In the last years, a great deal of effort has been devoted to profile plant gene expression following microorganism recognition. In addition, the phenotypes of transgenic and mutant plants in PA metabolism genes have been assessed. In this review, we integrate the current knowledge on this field and analyze the possible roles of these amines during the interaction of plants with microbes.

Interaction of plant cell signaling molecules, salicylic acid and jasmonic acid, with the mitochondria of Helicoverpa armigera

The cotton bollworm, Helicoverpa armigera is a polyphagous pest in Asia, Africa, and the Mediterranean Europe. Salicylic acid (SA) and jasmonic acid (JA) are the cell signaling molecules produced in response to insect attack in plants. The effect of these signaling molecules was investigated on the oxidative phosphorylation and oxidative stress of H. armigera. SA significantly inhibited the state III and state IV respiration, respiratory control index (RCI), respiratory complexes I and II, induced mitochondrial swelling, and cytochrome c release in vitro. Under in vivo conditions, SA induced state IV respiration as well as oxidative stress in time- and dose-dependent manner, and also inhibited the larval growth. In contrast, JA did not affect the mitochondrial respiration and oxidative stress. SA affected the growth and development of H. armigera, in addition to its function as signaling molecules involved in both local defense reactions at feeding sites and the induction of systemic acquired resistance in plants.

Evidence of a role for foliar salicylic acid in regulating the rate of post-ingestive protein breakdown in ruminants and contributing to landscape pollution

Ruminant farming is important to global food security, but excessive proteolysis in the rumen causes inefficient use of nitrogenous plant constituents and environmental pollution. While both plant and microbial proteases contribute to ruminal proteolysis, little is known about post-ingestion regulation of plant proteases except that activity in the first few hours after ingestion of fresh forage can result in significant degradation of foliar protein. As the signal salicylic acid (SA) influences cell death during both biotic and abiotic stresses, Arabidopsis wild-type and mutants were used to test the effect of SA on proteolysis induced by rumen conditions (39 °C and anaerobic in a neutral pH). In leaves of Col-0, SA accumulation was induced by exposure to a rumen microbial inoculum. Use of Arabidopsis mutants with altered endogenous SA concentrations revealed a clear correlation with the rate of stress-induced proteolysis; rapid proteolysis occurred in leaves of SA-accumulating mutants cpr5-1 and dnd1-1 whereas there was little or no proteolysis in sid2-1 which is unable to synthesize SA. Reduced proteolysis in npr1-1 (Non-expressor of Pathogenesis Related genes) demonstrated a dependence on SA signalling. Slowed proteolysis in sid2-1 and npr1-1 was associated with the absence of a 34.6 kDa cysteine protease. These data suggest that proteolysis in leaves ingested by ruminants is modulated by SA. It is therefore suggested that influencing SA effects in planta could enable the development of forage crops with lower environmental impact and increased production potential.

Salicylic acid is a modulator of catalase isozymes in chickpea plants infected with Fusarium oxysporum f. sp. ciceri

The relationship between salicylic acid level catalases isoforms chickpea cv. ICCV-10 infected with Fusarium oxysporum f. sp. ciceri was investigated. Pathogen-treated chickpea plants showed high levels of SA compared with the control. Two isoforms of catalases in shoot extract (CAT-IS and CAT-IIS) and single isoform in root extract (CAT-R) were detected in chickpea. CAT-IS and CAT-R activities were inhibited in respective extracts treated with pathogen whereas, CAT-IIS activity was not inhibited. These isoforms were purified and their kinetic properties studied in the presence or absence of SA. The molecular mass determined by SDS-PAGE of CAT-IS, CAT-IIS and CAT-R was found to be 97, 40 and 66 kDa respectively. Kinetic studies indicated that Km and V(max) of CAT-IS were 0.2 mM and 300 U/mg, 0.53 mM and 180 U/mg for CAT-IIS and 0.25 mM and 280 U/mg for CAT-R, respectively. CAT-IS and CAT-R were found to be more sensitive to SA and 50% of their activities were inhibited at 6 and 4 μM respectively, whereas CAT-IIS was insensitive to SA up to 100 μM. Quenching of the intrinsic tryptophan fluorescence of purified catalases were used to quantitate SA binding; the estimated K(d) value for CAT-IS, CAT-IIS and CAT-R found to be 2.3 μM, 3.1 mM and 2.8 μM respectively. SA is a modulator of catalase isozymes activity, supports its role in establishment of SAR in chickpea plants infected with the pathogen.

SA improvement of hyperhydricity reversion in Thymus daenensis shoots culture may be associated with polyamines changes

In shoot cultures of Thymus daenensis, hyperhydricity syndrome promoted by benzyladenine (BA) is characterised by the development of chlorophyll-deficient shoots with a high water content and reduced growth that is less differentiated. By removing the BA from the culture medium, the hyperhydricity was reversed, and the reversion toward a normal growth in vitro was more efficient in shoots treated with 5 μM of salicylic acid (SA), showing a significant increase in chlorophyll b after 4 weeks of culture. In the present study, the effect of salicylic acid on the reversion of shoot hyperhydricity was investigated at the level of the free, soluble and insoluble conjugated polyamine content. In T. daenensis micropropagated shoots, the level of polyamines was high, with a predominance of putrescine. BA, which triggered hyperhydricity, caused a reduction of the polyamine (PA) content by one-half due to a decrease in the putrescine content and insoluble conjugated PAs that were not detected in the hyperhydric shoots. In the reverted shoots, changes of the free polyamines, spermidine and, more notably, spermine, were shown. The spermine content doubled after 4 weeks of culture, and its amount was the same as that found in normal shoots, suggesting that free spermine could be particularly involved in the reversion of hyperhydricity. In the SA-reverted tissues, the PA pattern was marked with a transient increase of free putrescine, spermidine and spermine and an enhancement of soluble conjugated spermine. This transitory SA-dependent amplification of PAs was concomitant with a remarkable transient increase of H(2)O(2), suggesting that SA may be implicated in PA signalling pathways for tissue differentiation during the reversion of hyperhydricity in T. daenensis.