Influence of Systemic Signal Molecules on the Rate of Spread of the Immunizing Effect of Elicitors over Potato Tissues

Mobile systemic signal molecules (salicylic and jasmonic acids) enhance and accelerate the spread of the systemic immunizing effect of elicitors (arachidonic acid and chitosan) over potato tuber tissues (Solanum tuberosum L.).     

Effect of Arachidonic Acid on Potato Tubers during Storage

Potato (Solanum tuberosumL.) tubers were treated with various concentrations (10^–9to 10^–4M) of biogenic elicitor arachidonic acid during storage (from October to June). The data showed that the resistance-inducing concentration of arachidonic acid was 10^–6M in autumn and 10^–9M in spring. The possible causes of the change in the immunizing concentration of arachidonic acid during storage of potato tubers are discussed.     

Wound healing and induced resistance in potato tubers

It was demonstrated that biogenic elicitors, arachidonic acid and chitosan, locally and systemically stimulated wound healing in potato tuber tissues by increasing the number of wound periderm layers, accelerating the development of cork cambium (phellogen), and inducing proteinase inhibitors. The signal molecules, jasmonic and salicylic acids, had different effects on the development of wound periderm: jasmonic acid locally and systemically stimulated potato wound healing and elevated the level of proteinase inhibitors, whereas salicylic acid did not have any effect on wound healing and even blocked the formation of proteinase inhibitors.     

Beyond MHC: signals of elevated selection pressure on Atlantic salmon (Salmo salar) immune‐relevant loci

Using Atlantic salmon (Salmo salar) as a model system, we investigated whether 18 microsatellites tightly linked to immune‐relevant genes have experienced different selection pressures than 76 loci with no obvious association with immune function. Immune‐relevant loci were identified as outliers by two outlier tests significantly more often than nonimmune linked loci (22% vs. 1.6%). In addition, the allele frequencies of immune relevant markers were more often correlated with latitude and temperature. Combined, these results support the hypothesis that immune‐relevant loci more frequently exhibit footprints of selection than other loci. They also indicate that the correlation between immune‐relevant loci and latitude may be due to temperature‐induced differences in pathogen‐driven selection or some other environmental factor correlated with latitude.     

Effects of dimethylsulfoxide on the ultrastructure of fixed cells

It has been reported that the use of dimethylsulfoxide (DMSO) as a solvent for fixatives enhances preservation of cellular ultrastructure. By contrast, we have shown that DMSO alters the ultrastructural integrity of glutaraldehyde fixed cells. The cell membrane, nuclear envelope, endoplasmic reticulum, ribosomes, microtubules and intracytoplasmic organelles are most susceptible to the action of DMSO. We hypothesize that DMSO exerts intracellular alterations via its interaction with remnant interfacial water in fixed cells. DMSO-induced alterations of these and related cellular components may result in the formation of artefactual structures and networks. Thus, it appears that DMSO containing glutaraldehyde neither accelerates fixation nor enhances stabilization of cellular ultrastructure. For these reasons, addition of DMSO to fixatives is not recommended.     

Wound repair in plant tissues (Review)

Signaling systems responsible for repair processes in plants and manifestation of defensive effects in plant tissues were analyzed. Special attention was given to jasmonic acid, a mobile systemic repair signal, as well as to jasmonate biosynthesis and signal transport to the areas where protective responses of plants are induced. The main defense responses of potato tubers induced by wounding were considered.     

Electrochemistry of Escherichia coli JM109: direct electron transfer and antibiotic resistance

In this study, the cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques were used to investigate the extracellular electron transfer from Escherichia coli JM109. It was demonstrated that the formal redox potential of direct electron transfer between electrode and an E. coli JM109 cell in aerobic buffer corresponds to -0.42 V vs. Ag/AgCl. Based on the electroactivity of bacterial cells, the electrochemical system for definition of sensitivity of microbiological material to antibiotics cefepime, ampicillin, amikacin, and erythromycin was proposed. The results obtained indicate that with electrochemical methods it is possible to provide screening of potential drugs for bacterial diseases. The electrochemical method allows estimating the degree of E. coli JM109 cells resistance to antibiotics within 2-5h using disposable screen-printed graphite electrodes.     

Elicitor activity of chitosan and arachidonic acid: their similarity and distinction

Two elicitors-chitosan and arachidonic acid-induced the same defense responses in potatoes, stimulating the processes of wound reparation and inducing the formation of phytoalexins, inhibitors of proteinase, and active forms of oxygen. However, chitosan induced the defense potential of plant tissues at concentrations higher than those of arachidonic acid. The protective action of chitosan was defined by two parameters, i.e., the ability to induce the immune responses in plant tissues and to exhibit a toxic effect on the pathogen development, causing late blight and seedling blight, whereas the elicitor effect of arachidonic acid depended on its ability to induce the defense potential of plant tissues only.     

Effect of immunomodulators on potato resistance and susceptibility to Phytophthora infestans

The mechanisms of induced resistance and susceptibility of potato (Solanum tuberosum L.) tubers to late blight agent (Phytophthora infestans Mont de Bary) were studied using an elicitor chitosan and an immunosuppressor laminarin. It was elucidated that treatment of disks from potato tubers with chitosan resulted in salicyclic acid (SA) accumulation due to activation of benzoate-2-hydroxylase and hydrolysis of SA conjugates. Such SA accumulation in potato tissues inhibited one of the antioxidant enzymes, catalase, inducing an oxidative burst and resistance development. The mechanisms of induced susceptibility to the late blight causal agent were studied using an unspecific immunosuppressor, laminarin, an analogue of natural specific suppressor of potato immune responses, β-1,3,β-1,6-glucan. It was established that the development of immunosuppression in tissues treated with laminarin did not affect the SA level in tissues. However, catalase sensitivity to SA reduced in laminarin-treated tissues, and the enzyme activity increased. In its turn, this might result in the reduced level of hydrogen peroxide in the cells and, as a sequence, in the increased potato susceptibility to late blight.