Free and conjugated forms of salicylic acid: Their content and role in the potato

Hydrolysis of conjugated forms of salicylic acid and accumulation of its free form was observed after infection of potato tubers (Solanum tuberosum L.) with an incompatible race of phytophthora or treatment with an elicitor (chitosan). Infection of tubers with a compatible race of the pathogen or treatment with a suppressor (laminarin) decreased both the degree of hydrolysis of conjugated forms of salicylic acid and the accumulation of its free form.__________Translated from Prikladnaya Biokhimiya i Mikrobiologiya, Vol. 41, No. 3, 2005, pp. 354–357.Original Russian Text Copyright © 2005 by Panina, Vasyukova, Ozeretskovskaya.     

Effects of salicylic and jasmonic acids on the components of pro/antioxidant system in potato plants infected with late blight

The effects of salicylic acid (SA) and jasmonic acid (JA) on plant defense responses were studied with aseptic potato (Solanum tuberosum L.) plantlets infected with Phytophthora infestans (Mont.) de Bary. Plant treatment with 10⁻⁶ M SA or 10⁻⁷ M JA induced plant resistance; the mixture of these acids was most efficient. After treatment with these compounds, phenolic compounds were accumulated and peroxidase was activated in the sites of pathogen localization, and this might be the reason of resistance enhancement. In addition, more H₂O₂ was accumulated in infected plants treated with JA or its mixture with SA but not in plants treated with SA alone. It might occur because of observed inhibition of catalase and activation of isoperoxidase with the isoelectric point (pI) of ∼9.3, which manifests an affinity for the pathogen cell wall. The data obtained allow us to recommend the application of these compounds for potato plant protection against late blight.     

Free and conjugated forms of salicylic acid: content and role in potato

Hydrolysis of conjugated forms of salicylic acid and accumulation of its free form was observed after infection of potato tubers (Solanum tuberosum L.) with an incompatible race of phytophthora or treatment with an elicitor (chitosan). Infection of tubers with a compatible race of the pathogen or treatment with a suppressor (laminarin) decreased both the degree of hydrolysis of conjugated forms of salicylic acid and the accumulation of its free form.     

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.     

Biochemical reactions of different tissues of potato (Solanum tuberosum) to zoospores or elicitors from Phytophthora infestans

The time courses of sesquiterpenoid phytoalexin accumulation were examined in compatible and incompatible interactions of leaves and tubers from five different R genotypes of potato (Solanum tuberosum) with corresponding pathotypes of Phytophthora infestans, as well as in non-host interactions of all five potato cultivars with Phytophthora megasperma f. sp. glycinea and in elicitor-treated tubers from five, and cell suspension cultures from two, of the cultivars. In tubers, rishitin and several structurally related sesquiterpene derivatives accumulated rapidly in non-host incompatible interactions, less rapidly in host incompatible interactions, and more slowly in compatible interactions. Treatment of tubers or cell cultures with fungal culture filtrate or arachidonic acid elicited in most cases a transient accumulation of the sesquiterpenoid phytoalexins. None of these compounds was detectable under any of the applied conditions either in infected or in elicitortreated leaves. Sesquiterpenoid phytoalexins might therefore be helpful, but appear not to be essential, in disease resistance of potato.Abbreviations CF concentrated culture filtrate of Pi - cv. cultivar - Pi Phytophthora infestans (numbering indicates pathotypes corresponding to R genes in potato) - Pmg Phytophthora megasperma f. sp. glycinea     

Involvement of salicylic acid in induction of nematode resistance in plants

The role of salicylic acid (SA) as a possible signaling component in the case of the infection of plants with nematodes has been studied using a model system consisting of the tomato (Lycopersicon esculentum (Mill.) and race 1 of the gall eelworm Meloidogyne incognita (Kofoid and White, 1919; Chitwood, 1949). The preplanting SA treatment of tomato seeds results in an increased nematode resistance of susceptible tomato cultivars; the protective effect is higher in the case of SA combined with chitosan, a biogenic elicitor of plant resistance. The studied preparations stimulate the growth and development of the plants. The increase in the resistance of tomato plants is related to the increased activity of phenylalanine ammonia-lyase and an increased SA content in plant tissues infected with nematodes; both these factors significantly influence nematode development.     

Effects of salinity on the contents of polyamines and some other compounds in sunflower plants differing in salt tolerance

The effects of salt stress (50, 100, and 150 mM NaCl) on the levels of free, bound, and total polyamines were studied in the leaf tissues of salt-tolerant (Coban) and salt-sensitive (Sanbro) cultivars of sunflower (Helianthus annuus L.) plants grown for 15 or 25 days under salinity. The amounts of free, acid-soluble bound, and total spermine increased in leaf tissues of sunflower plants subjected to salt stress while the levels of other polyamines decreased or no significant changes occurred. The increase in some PA titers suggests their potential role in overcoming the adverse effect of salinity stress. The salt sensitivity of the sunflower plants was associated with the excessive accumulation of total polyamines in the leaf tissues of salt-sensitive cultivar (Sanbro) under saline condition. The content of other compounds such as proline, protein, and ions (Na⁺, K⁺, Cl^-, K⁺/Na⁺) in leaf tissue changed depending on salt concentration and the cultivars used.From Fiziologiya Rastenii, Vol. 52, No. 1, 2005, pp. 36–42.Original English Text Copyright © 2005 by Mutlu, Bozcuk.This article was presented by the authors in English.     

Temporal and spatial patterns of 1, 3-β-glucanase and chitinase induction in potato leaves infected by Phytophthora infestans

Infection of potato (Solarium tuberosum L.) leaves with the fungal pathogen Phytophthora infestans caused a similar, strong and coordinated induction of 1, 3-β-glucanases and chitinases in compatible (plant susceptible) and incompatible (plant resistant) interactions of two selected plant cultivars with appropriate races of the fungus. The temporal and spatial patterns of 1, 3-β-glucanase induction were studied in further detail by immunohistochemical and in-situ hybridization methods. Accumulation of the protein was preceded by progressive activation of the corresponding gene, commencing near infection sites and spreading rapidly throughout the whole infected leaf as well as to adjacent, non-infected leaves. Protein and mRNA distribution patterns were nearly identical in compatible and incompatible interactions. In comparison with 1, 3-β-glucanase mRNA, phenyl-alanine ammonia-lyase mRNA accumulated more rapidly and remained restricted to the vicinity of fungal infection sites, in addition to its constitutive occurrence in the vascular bundles. Even more rapid than any detectable mRNA induction was the accumulation of auto fluorescing material in plant cells immediately surrounding fungal structures, particularly and invariably in incompatible interactions and less frequently in compatible interactions. It is concluded that cultivar-race-specific resistance is established early in the interaction of potato leaves with P. infestans and hence the observed massive accumulation of 1, 3-β-glucanase and chitinase is presumably not involved in determining this specificity.     

In situ localization of PR-1 mRNA and PR-1 protein in compatible and incompatible interactions of pepper stems withPhytophthora capsici

Summary In situ hybridization and immunogold labeling were performed to examine the temporal and spatial expression pattern of pathogenesis-related protein 1 (CABPR1) mRNA and PR-1 protein in pepper (Capsicum annuum L.) stem tissues infected by virulent and avirulent isolates ofPhytophthora capsici. CABPR1 mRNA accumulation was confirmed in the infected pepper stem tissue by Northern blot analysis and in situ hybridization. Northern blot analysis showed that the temporal expression ofCABPR1 mRNA varied greatly between compatible and incompatible interactions. An earlier expression of theCABPR1 gene, 6 h after inoculation, was observed in the incompatible interaction. In situ hybridization results revealed thatCABPR1 mRNA was expressed in the phloem areas of vascular bundles in infected pepper stem tissues, but especially strongly in the incompatible interaction. PR-1 protein was predominantly found in the intercellular spaces of pepper stem cells in the compatible and incompatible interactions 24 h after inoculation. Strikingly, the immunogold labeling was associated with fibrillar and electron-dense material localized in the intercellular space. Dense labeling of PR-1 protein was also seen at the interface of the pathogen and the host cell wall, whereas few gold particles were detected over the host cytoplasm. However, PR-1 protein was not detected over the fungal cell wall in either interaction.     

Effect of wounding or infection by Phytophthora infestans on the contents of terpenoids in potato tubers

Inoculation of the potato cut surfaces with an incompatiblerace of Phytophthora infestans induced an accumulation of rishitin,but only a trace occurred when infected by a compatible race.When the tuber was cut, a large amount of steroid-glycoalkaloids(solanine) accumulated in the cut surface tissue, although onlya trace was found in intact tissue. Only a small amount of solanine,if any, was contained in the wound periderm tissue. Most ofthe solanine seemed to be distributed in tissue neighbouringthe newly formed meristematic tissue zone. Distribution of solanineas a function of distance from the cut surface was exponential.Infection of the cut surface by an incompatible race of Phytophthorainfestans reduced the accumulation of solanine. The higher theconcentration of zoospore used, the less the solanine content.It has been reported that the higher the concentration of zoosporesused for inoculation of the cut surface, the less the numberof renewed meristematic cells in the wound tissue. In experimentsusing fresh and aged tubers, a good correlation between thenumber of renewed meristematic cells and solanine content wasfound. The accumulation of solanine in the wound tissue andits reduction due to infection by an incompatible race may berelated to renewed meristematic cells formation and its reductioncaused by the infection. No drastic change in carotenoids or sterol contents was found2 days after cutting or inoculation, when the tubers were cut,or cut and then infected by the incompatible race. ¹ Studies on the phytoalexin (No. 10). (6) in References constitutes"Studies on the phytoalexin No. 9". ² Present adress: Plant Pathology Laboratory, Faculty of Agriculture,Nagoya University, Chikusa-ku, Nagoya, 464, Japan. (Received April 1, 1972; )     

Expression of the Phytophthora infestans ipiB and ipi0 genes in planta and in vitro

The ipiB and ipiO genes of the potato late blight fungus Phytophthora infestans (Mont.) de Bary were isolated from a genomic library in a screen for genes induced in planta. Expression of these genes was studied during pathogenesis on various host tissues and different host plants, some of which show specific resistance against P. infestans infection. During pathogenesis on leaves and tubers of the fully susceptible potato cultivar (cv.) Ajax and on leaves of the fully susceptible tomato cv. Moneymaker, the P. infestans ipiB and ipiO genes show a transient expression pattern with highest mRNA levels in the early stages of infection. During the interaction with leaves of the partially resistant potato cv. Pimpernel, the expression is also transient but accumulation and disappearance of the mRNAs is delayed. Also in P. infestans inoculated onto a race-specific resistant potato cultivar and onto the nonhost Solanum nigrum, ipiB and ipiO mRNA is detectable during the initial stages of infection. Apparently, the expression of the ipiB and the ipiO genes is activated in compatible, incompatible and nonhost interactions. In encysted zoospores, ipiB and ipiO mRNA accumulation was not detectable, but during cyst germination and appressorium formation on an artificial surface the genes are highly expressed. Expression studies in mycelium grown in vitro revealed that during nutrient starvation the expression of the ipiB and ipiO genes is induced. For ipiO gene expression, carbon deprivation appeared to be sufficient. The ipiO gene promoters contain a sequence motif that functions as a glucose repression element in yeast and this motif might be involved in the regulation of ipiO gene expression.     

The effect of wheat seed presowing treatment with salicylic acid on its endogenous content,activities of respiratory pathways,and plant antioxidant status

We studied the effects of wheat (Triticum aestivum L.) seed presowing treatment with 0.05 mM salicylic acid (SA) on its endogenous content and the ratio of free to bound forms in seedling shoots and roots. During two-week-long seedling growth, we observed a gradual decrease in the total SA content in shoots but not in roots. In shoots, the content of conjugated SA increased and that of its free form reduced. Seed presowing treatment with SA reduced total content of endogenous SA in both seedling shoots and roots. The content of free SA reduced intensely in shoots and somewhat less in roots. Such reduction was supposed to occur due to the disturbance in SA biosynthesis. These were accompanied by the increases in the shoot and especially root biomass and length, stimulation of total dark respiration, and changes in the ratio between respiratory pathways. In the roots, we observed an increased proportion of cytochrome respiration, whereas in the shoots — alternative cyan-resistant respiration. We also observed changes in the plant antioxidant system. A degree of lipid peroxidation was stronger in shoots than in roots. Pretreatment with SA resulted in MDA 2.5-fold accumulation in shoots, whereas its content in roots reduced by 1.7 times. We concluded that the type and intensity of SA effects on plant growth, energetic balance, and antioxidant status were related to changes in its endogenous content and redistribution between free and conjugated forms.     

Activation of elicitor defensive properties by systemic signal molecules during the interaction between potato and the late blight agent

The elicitor arachidonic acid in combination with jasmonic acid (JA) induced a higher level of defense against the late blight agent in potato (Solanum tuberosum L.) tissues than in combination with salicylic acid (SA). On the contrary, the elicitor chitosan displayed a higher inductive effect in combination with SA as compared with JA. The optimal concentrations of tested compounds were selected for designing the compositions activating wound repair, induction of proteinase inhibitors, and resistance to the biotrophic pathogen Phytophthora infestans (Mont.) de Bary. It was demonstrated that the compositions of elicitor and systemic signal molecules provided a faster spreading of an inducing effect in the potato tissues.     

Expression of three osmotin-like protein genes in response to osmotic stress and fungal infection in potato

We have characterized three cDNAs encoding osmotin-like proteins from potato (Solanum commersonii) cell cultures. These cDNAs (pA13, pA35, and pA81) have extensive nucleotide identity in the coding regions but low homology in the 3 non-coding sequences, and may encode three isoforms of potato pathogenesis-related (PR) type 5 proteins. Using gene-specific probes, RNA gel blot analyses showed constitutive accumulation of osmotin-like protein mRNAs in cell cultures, leaves, stems, roots and flowers, with high abundance in the roots and mature flowers. Treatments with abscisic acid (ABA), low temperature, and NaCl increased the accumulation of all three mRNAs in S. commersonii cell cultures and plants grown in vitro. Salicylic acid (SA), and wounding resulted in a moderate increase in the levels of pA13 and pA81 but not pA35 mRNAs. Infection with the fungus Phytophthora infestans activated strong and non-systemic expression of all three osmotin-like protein genes. The accumulation of osmotin-like proteins, however, was detected only in P. infestans-infected tissues but not in plants treated with ABA, SA, NaCl, low temperature, or wounding.     

Tobacco-mosaic-virus-induced increase in abscisic-acid concentration in tobacco leaves:

The concentrations of free and bound abscisic acid (ABA and the presumed ABA glucose ester) increased three- to fourfold in leaves of White Burley tobacco (Nicotiana tabacum L.) systemically infected with tobacco mosaic virus. Infected leaves developed a distinct mosaic of light-green and dark-green areas. The largest increases in both free and bound ABA occurred in dark-green areas. In contrast, virus accumulated to a much higher concentration in light-green tissue. Free ABA in healthy leaves was contained predominantly within the chloroplasts while the majority of bound ABA was present in non-chloroplastic fractions. Chloroplasts from light-green or dark-green tissues were able to increase stromal pH on illumination by an amount similar to chloroplasts from healthy leaf. It is unlikely therefore that any virus-induced diminution of pH gradient is responsible for increased ABA accumulation. Tobacco mosaic virus infection had little effect on free ABA concentration in chloroplasts; the virus-induced increase in free ABA occurred predominantly out-side the chloroplast. The proportional distribution of bound ABA in the cell was not changed by infection. Treatment of healthy plants with ABA or water stress increased chlorophyll concentration by an amount similar to that induced by infection in dark-green areas of leaf. A role for increased ABA concentration in the development of mosaic symptoms is suggested.Abbreviations ABA abscisic acid - TMV tobacco mosaic virus     

Role of Surface Substances on Germinated Spores of Ceratosystis fimbriata,Black Rot Fungus,in Host-parasite Interaction

Surface substances were isolated by sonication from the germinated spores of various strains of Ceratocystis fimbriata and characterized in relation to host-parasite specificity. The substances from the sweet potato strain, compatible with sweet potato, potently inhibited the spore agglutination of various strains by spore-agglutinating factor from sweet potato roots, while the substances from incompatible strains, that is, coffee, taro, and almond strains, weakly inhibited this agglutination. The substances from the sweet potato strain increased ethylene production from sweet potato roots infected by all strains tested, sweet potato, coffee, taro, and almond strains, which was possibly an index of pathogenicity. On the other hand, the substances from incompatible strains, coffee, taro, and almond strains, suppressed the ethylene production from the tissue infected by all four strains except the substances from almond strains on almond strain. Heat and trypsin treatments inactivated the spore agglutination inhibitory activity of the surface substances. Coincidently, these treatments extinguished the effect of the surface substances on pathogenicity of C. fimbriata on sweet potato roots.