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  • Open access
  • 123 Reads
Influence of Bacillus Subtilis and Stress Phythormones on the Content of H2O2, Expression of Protective Proteins Genes and Proteome of Potato Leaves When Infected with Phytophthora infestans Mont de Bary in Conditions of Soil Dry

The effect of bacteria Bacillus subtilis strain 26D in combination with stress phytohormones – salicylic (SA) and jasmonic (JA) acids, on the content of H2O2, transcriptional activity of genes of pathogen-induced (PR) proteins (PR-1, PR-6, PR-9 ) and a change in the spectrum of potato (Solanum tuberosum L.) leaves proteins in connection with development of resistance to the causative agent of late blight – oomycete Phytophthora infestans (Mont.) de Bary against the background of a lack of moisture in soil have been investigated. Plants grown from microtubers on a soil substrate in containers treated with B. subtilis suspension (108 cells / ml) and with a mixture of bacteria with SA (10-6 M), JA (10-7 M), SA + JA (1:1 ratio), then were infected with P. infestans zoospores (107 spores / ml) and cultivated under artificial drought conditions. Some of treated plants were left uninfected. A significant decrease in degree of P. infestans leaf infection was revealed under influence of B. subtilis treatment in combination with JA. An increase in potato resistance was mediated by a stimulating effect on the concentration of H2O2 and on the transcriptional activity of PR-protein genes in plant tissues. Using two-dimensional electrophoresis we have revealed the differences in the content of 19 polypeptides in the pI range 4.0 to 9.0 and MW range 30 to 125 kDa. On the basis of cluster and factor analyzes, it was shown that treatment of B. subtilis plants most significantly changes the spectrum and relative content of individual proteins in both healthy and infected plants. Probably, stress phytohormones activate plant defense mechanisms aimed at the generation of Н2О2 and preventing the change in the spectrum of protective proteins induced by symbiotic bacteria. The most significant factor determining the change in the proteome of P. infestans infected potato plants against the background of drought is the combination of B. subtilis with JA.

  • Open access
  • 98 Reads
Control of Carrot Seed-Borne Pathogens by Aromatic Plants Distillates

Global warming, pollution problems, and the demand for sustainable food production forced farmers to find new solutions for biological plant protection. Usage of natural renewable sources around us seems to be an alternative. Compounds isolated from other plants and distinguished with antifungal properties can be used to protect vegetables from the seed-borne pathogens. The study aimed to elucidate the ability of essential oils of Juniperus communis L., Hyssopus officinalis L. and Thymus vulgaris L. to control carrot seed-borne pathogen Alternaria spp. The agar-plate method was used for carrot seeds infestation with micromycetes. Essential oils extracted from common juniper, hyssop and thyme, then separately mixed with potato dextrose agar media at different concentrations and the antifungal activity of each oil tested in vitro. The results revealed that the T. vulgaris essential oil (200–1000 μL L-1) significantly inhibited Alternaria spp. growth. The H. officinalis essential oil even promoted seed damage the second and fifth day of the evaluation compared to control; however, the concentration of 400 μL L-1 showed little suppression of micromycete development 7 days after inoculation. In vitro experiments indicated that 600 μL L-1 of J. communis essential oil could control seed-borne pathogen viability. Overall, thyme essential oil expressed a high potential for application in biofungicides formulations.

  • Open access
  • 140 Reads
Modelling biocontrol agents as plant protection tools

In recent years, researchers have been increasingly explored sustainable tools for plant protection against pathogens, including the use of biological control agents (BCAs), which have the potential to complement or replace chemical fungicides. However, global reliance on their use remains relatively insignificant and the factors influencing their efficacy remain unclear. The complex interactions among a target pathogen, a host plant, and the BCA population in a changing environment can be studied by process-based, weather-driven mathematical models, able to interpret the combined effects on BCA efficacy of: (i) BCA mechanism of action, (ii) timing of BCA application with respect to timing of pathogen infection (preventative vs. curative), (iii) temperature and moisture requirements for both pathogen and BCA growth, and (iv) BCA survival capability. When the model was used under three contrasting weather conditions for the control of Botrytis bunch rot in grapevine, BCA efficacy was mostly influenced by environmental conditions, accounting for > 90% of the variance in simulated biocontrol efficacy. These findings indicate that the environmental responses of BCAs should be considered during their selection, BCA survival capability should be considered during both selection and formulation, and weather conditions and forecasts should be considered at the time of BCA application in the field. Different commercial BCAs for the control of Botrytis cinerea showed different environmental requirements and adaptation capabilities; therefore, the most suitable BCA to be used for a specific field application may consider weather conditions and forecasts at the time of intervention.

  • Open access
  • 243 Reads
A Three-Way Interaction System for Understanding the Ability of Trichoderma spp. to Trigger Defenses in Tomato Challenged by Phytophthora nicotianae

The understanding of the genetics of plant-defense mechanisms, which are triggered by microbial beneficial antagonists of plant pathogens during an infection process, represents a new challenge for modern Plant Pathology. This study evaluated the differential expression of plant-defense related genes during a three-way interaction plant - antagonist - pathogen in the model system tomato - Trichoderma – the oomycete Phytophthora nicotianae.
Thirty-day-old tomato seedlings were treated at the root system with a suspension of germinated conidia of two selected strains of T. asperellum and T. atroviride and then inoculated with zoospores of P. nicotianae. The defense mechanisms activated by tomato plants upon the simultaneous colonization of the root system by Trichoderma spp. and P. nicotianae were evaluated by analysing the expression of genes involved in the main plant defense pathways, namely salicylic acid (i.e.: pathogenesis-related proteins - PR1b1 and PR-P2-encoding genes), jasmonic acid (i.e.: lipoxygenases enzymes - TomLoxC and TomLoxA-encoding genes) and the tomato plant defensin protein (i.e.: SlyDF2-encoding gene) strongly involved in the tomato-Phytophthora infection process.
It was shown that during the three-way interaction, in the P. nicotianae-inoculated seedlings the PR1b1-encoding gene was up-regulated exclusively in the treatment with T. atroviride strain, while PR-P2- and SlyDF2-encoding genes were up-regulated by both T. asperellum and T. atroviride strains, supporting the hypothesis that Trichoderma can strongly elicit the expression of these plant defense mechanisms on tomato plants. Conversely, both lipoxygenase encoding-genes (i.e.: TomLoxC and TomLoxA) resulted normally expressed in all treatments.
In conclusion, this study provided a contribution to understand the attitude of Trichoderma to trigger plant-defense mechanisms during P. nicotianae infections on tomato.

  • Open access
  • 139 Reads
Green Leaf Volatiles: Airborne Signals that Protect against Biotic and Abiotic Stresses

Green leaf volatiles (GLVs) are rapidly released by plant leaves upon damage. This makes them ideal signals to convey the presence of a damaging threat to other parts of the same plant, but also to plants nearby. There, GLVs were first found to activate defense responses against insect herbivores and necrotrophic pathogens. Aside from providing direct protection, GLVs also prime those responses resulting in an enhanced and/or accelerated response to these biotic stressors. Recently, it was shown that GLVs also provide protection against cold stress in plants, resulting in stress-specific transcript accumulation and subsequent reduced damage. Interestingly, this response was further associated with a stimulation of growth after the stress subsided. However, this growth compensation was only observed in cold stressed plants while control plants continued to grow normally. Common to all those stresses is that they can also cause the release of these compounds and it is safe to assume that this correlation lies at the evolutionary origin of their biological activity. However, the quantities and qualities of the emitted GLVs can vary significantly even in closely related species, suggesting that eco-physiological factors related to biotic and abiotic stresses may have been the driving force for the highly variable emission of these compounds. However, too little is known about the regulation of GLV emissions, signaling, and responses to support this hypothesis. In this presentation we will provide an overview of current knowledge regarding biosynthesis and signaling of GLVs in plants and will give an outlook into future areas of research that may provide essential information about the complex biological activities of these compounds.

  • Open access
  • 142 Reads
Use of molecular dynamics to decipher the binding of salicylic acid to proteins: Example of Arabidopsis thaliana Chloroplastic GAPDH-A1

Salicylic acid (SA) has an essential role in the responses of plants to pathogens. SA initiates defense signaling cascades via binding to proteins. NPR1 is a transcriptional co-activator and is a key target of SA binding. Many other proteins have been shown to bind SA. Amongst these proteins are important enzymes of primary metabolism. Here, we detail that the A1 isomer of chloroplast glyceraldehyde 3-phosphate dehydrogenase (GAPA1) from Arabidopsis thaliana binds SA, as shown in surface plasmon resonance experiments. Besides, we show that SA inhibits its GAPDH activity in vitro. To gain some insight into the underlying molecular interactions and binding mechanism, we combined in silico molecular docking experiments and molecular dynamics simulations on the free protein and protein–ligand complex. The molecular docking analysis yielded to the identification of two putative binding pockets for SA. A simulation in water of the complex between SA and the protein allowed us to determine that only one pocket—a surface cavity around Asn35—would efficiently bind SA in the presence of solvent. The importance of this is further supported through experimental biochemical assays. Indeed, mutating GAPA1 Asn35 into Gly or Arg81 into Leu strongly diminished the ability of the enzyme to bind SA. The very same cavity is responsible for the NADP+ binding to GAPA1. NADH inhibited, in a dose-response manner, the binding of SA to GAPA1, validating our data. The use of the methodology to study SA binding to other proteins will be discussed at the end of the talk.

  • Open access
  • 97 Reads
Beneficial microorganisms: the best partner to improve plant adaptative capacity

Currently, the world is facing a high population increase as well as climate change involving global warming, water shortage which limits agronomic productivity, necessary to achieve food security for the growing population. As sessile organisms unable to run away from danger, plants are endowed with sophisticated mechanisms to overcome all stressing situations for survival, involving an enormous amount of chemical molecules, specific for each situation. In addition, they establish intimate relationships with beneficial microorganisms creating the plant microbiome. Within this microbiome are beneficial bacteria, known as Plant Growth Promoting Rhizobacteria (PGPR), which represent a great tool to boost plant fitness in different aspects, as they are able to trigger multiple targets simultaneously.

The present work describes the physiological mechanisms involved in plant adaptation to water stress, nutrient absorption, and adaptative responses to biotic stress and how bioeffectors are able to modulate these responses, focusing on the mechanisms involved in plant adaptation to water stress (salinity and water shortage), plant innate immunity and general mechanisms involved in plant protection to pathogen outbreaks. A few examples in Solanum lycopersicum, Olea europea and Rubus sp illustrate effects of PGPR increasing plant adaptative capacity.

  • Open access
  • 82 Reads
Remodeling of carbon and nitrogen metabolites in durum wheat: a simple response to complex stimuli

Plant stress studies dealing with a single stress approach have been useful for dissecting stress perception of defined stimuli and related gene expression and metabolic changes. However, in real-world scenarios plants are simultaneously exposed to a plethora of stresses counteracted by mean of tailored responses completely different from the responses to individual stresses. Durum wheat seedlings were used as experimental model to investigate the plant response to salinity (100 mM NaCl) and low/high light (350/900 μmol m–2 s–1) or low/high nitrogen (0.1/10mM KNO3, respectively), focusing on the physiological and metabolic changes potentially involved in osmotic adjustment and antioxidant defense. The data showed that durum wheat plants are able to fine-tune relatively few selected metabolites, in particular proline, amides, GABA, minor amino acids, hexoses and glycine betaine, which may be the key actors in osmotic adjustment, scavenging of ROS, biochemical pH-stat, assimilation of the excess of ammonium, and signaling under the combined stresses. To unravel, in particular, the reason of proline, glycine betaine and GABA accumulation and their possible mode of action, all possible roles for these metabolites under stress are considered, and mechanisms of action triggered by stresses suggested.

  • Open access
  • 84 Reads
Plant Molecular Responses to Salt Stress

Plants are frequenly exposed to environmental changes. In fact, abiotic stresses are the most serious
factors limiting the productivity of agricultural crops, with adverse effects on germination, plant
vigor and crop quality and yield. In particular, salinity stress is a global problem widespread that affects over 800 million ha. In the Mediterranean area, seawater intrusion into freshwater aquifers highly contribute to soil salinisation, resulting in crops productivity decrease. Responses to abiotic stresses are complicated pathways involving the interaction of different signalling molecules to coordinate a specific metabolic pathways. The regulation of these responses involves transcriptional factors, which regulate gene expression by binding to specific DNA promoter sequences. Transcription factors involved in salt stress responses include DRE-related binding factors, leucine zipper DNA binding proteins, putative zinc finger proteins, myb proteins, bZIP / HD-ZIPs, and AP2 / EREBP. Particularly, AP2 / ERF domain proteins include the DREB or CBF proteins binding to dehydration response elements (DRE) or C-repeats. Transcription factors are powerful targets for genetic engineering in abiotic stress resistance in crops and many studies have been focused on this topic.

  • Open access
  • 89 Reads
Comparative and functional screening of three species traditionally used as antidepressants: Valeriana officinalis L., Valeriana jatamansi Jones ex Roxb. and Nardostachys jatamansi (D.Don) DC.

The essential oils (EOs) of three Caprifoliaceae species, the Eurasiatic Valeriana officinalis (Vo), the Himalayan Valeriana jatamansi (Vj) and Nardostachys jatamansi (Nj), are traditionally used to treat neurological disorders. Roots/rhizomes micromorphology, DNA barcoding and EOs phytochemical characterization were carried out, while biological effects on the nervous system were assessed by acetylcholinesterase (AChE) inhibitory activity and microelectrode arrays (MEA). Nj showed the highest inhibitory activity on AChE (IC50 67.15 μg/mL) followed by Vo (IC50 127.30 μg/mL) and Vj (IC50 246.84 μg/mL). MEA analyses on rat cortical neurons, carried out by recording Mean Firing Rate (MFR) and Mean Bursting Rate (MBR), revealed stronger inhibition by Nj (IC50 18.8 and 11.1 μg/mL) and Vo (16.5 and 22.5 μg/mL), compared with Vj (68.5 and 89.3 μg/mL). These results could be related to different EOs composition, since sesquiterpenes and monoterpenes significantly contribute to the observed effects, but the presence of oxygenated compounds such as aldehydes and ketones is a discriminating factor in determining the order of potency. Our multidisciplinary approach represents an important tool to avoid the adulteration of herbal drugs and permits the evaluation of the effectiveness of EOs that could be used for a wide range of therapeutic applications.