Showing papers on "Phytoalexin published in 1999"
TL;DR: Results indicate that SA-independent compensation pathways that do not operate in NahG plants are active in sid mutants, and one of the mutants is allelic to eds5 (for enhanced disease susceptibility), whereas the other mutant has not been described previously.
Abstract: In Arabidopsis, systemic acquired resistance against pathogens has been associated with the accumulation of salicylic acid (SA) and the expression of the pathogenesis-related proteins PR-1, PR-2, and PR-5. We report here the isolation of two nonallelic mutants impaired in the pathway leading to SA biosynthesis. These SA induction-deficient (sid) mutants do not accumulate SA after pathogen inoculation and are more susceptible to both virulent and avirulent forms of Pseudomonas syringae and Peronospora parasitica. However, sid mutants are not as susceptible to these pathogens as are transgenic plants expressing the nahG gene encoding an SA hydroxylase that degrades SA to catechol. In contrast to NahG plants, only the expression of PR-1 is strongly reduced in sid mutants, whereas PR-2 and PR-5 are still expressed after pathogen attack. Furthermore, the accumulation of the phytoalexin camalexin is normal. These results indicate that SA-independent compensation pathways that do not operate in NahG plants are active in sid mutants. One of the mutants is allelic to eds5 (for enhanced disease susceptibility), whereas the other mutant has not been described previously.
879 citations
TL;DR: Evidence in support of phytoalexins in resistance as well some recent advances in phy toalexin biosynthesis are reviewed and criteria for evaluating a role for phy ToALxin in disease resistance are discussed.
Abstract: One of the best and longest-studied defense response of plants to infection is the induced accumulation of antimicrobial, low-molecular-weight secondary metabolites known as phytoalexins. Since the phytoalexin hypothesis was first proposed in 1940, a role for these compounds in defense has been revealed through several experimental approaches. Support has come, for example, through studies on the rate of phytoalexins in relation to cessation of pathogen development, quantification of phytoalexins at the infection site, and relationship of pathogen virulence to the phytoalexin tolerance. Evidence in support of phytoalexins in resistance as well some recent advances in phytoalexin biosynthesis are reviewed. Criteria for evaluating a role for phytoalexins in disease resistance are also discussed.
558 citations
TL;DR: Camalexin production could not be triggered by exogenous application of either salicylate, ethylene or jasmonate and was not, or not strongly, reduced in mutants with defects in perception of these defense-related signal molecules, which appears to be a key determinant in resistance to at least A. brassicicola.
Abstract: Summary The phytoalexin-deficient Arabidopsis mutant pad3-1, which is affected in the production of the indole-type phytoalexin camalexin, has previously been shown not to display altered susceptibility to either the bacterium Pseudomonas syringae (Glazebrook and Ausubel, 1994; Proc. Natl. Acad. Sci. USA, 91: 8955‐8959) or the biotrophic fungi Peronospora parasitica (Glazebrook et al., 1997; Genetics, 146: 381‐392) and Erysiphe orontii (Reuber et al., 1998; Plant J. 16: 473‐485). We now show that this mutant is markedly more susceptible than its wild-type parental line to infection by the necrotrophic fungus Alternaria brassicicola, but not to Botrytis cinerea. A strong camalexin response was elicited in wild-type plants inoculated with either Alternaria brassicicola or Botrytis cinerea, whereas no camalexin could be detected in pad3-1 challenged with these fungi. Hence, PAD3 appears to be a key determinant in resistance to at least A. brassicicola. The induction of salicylate-dependent and jasmonate/ethylene-dependent defense genes was not reduced in Alternaria-challenged pad3-1 plants compared to similarly treated wild-type plants. Camalexin production could not be triggered by exogenous application of either salicylate, ethylene or jasmonate and was not, or not strongly, reduced in mutants with defects in perception of these defenserelated signal molecules. Camalexin-production appears to be controlled by a pathway that exhibits little crosstalk with salicylate-, ethylene- and jasmonate-dependent signalling events.
442 citations
TL;DR: This paper showed that PAD3 almost certainly encodes an enzyme required for camalexin biosynthesis, which is a cytochrome P450 monooxygenase, similar to those from maize that catalyze synthesis of the indole-derived secondary metabolite 2,4-dihydroxy-1, 4-benzoxazin-3-one.
Abstract: Phytoalexins are low molecular weight antimicrobial compounds that are synthesized in response to pathogen attack. The phytoalexin camalexin, an indole derivative, is produced by Arabidopsis in response to infection with the bacterial pathogen Pseudomonas syringae. The phytoalexin deficient 3 (pad3) mutation, which causes a defect in camalexin production, has no effect on resistance to P. syringae but compromises resistance to the fungal pathogen Alternaria brassicicola. We have now isolated PAD3 by map-based cloning. The predicted PAD3 protein appears to be a cytochrome P450 monooxygenase, similar to those from maize that catalyze synthesis of the indole-derived secondary metabolite 2,4-dihydroxy-1, 4-benzoxazin-3-one. The expression of PAD3 is tightly correlated with camalexin synthesis and is regulated by PAD4 and PAD1. On the basis of these findings, we conclude that PAD3 almost certainly encodes an enzyme required for camalexin biosynthesis. Moreover, these results strongly support the idea that camalexin does not play a major role in plant resistance to P. syringae infection, although it is involved in resistance to a fungal pathogen.
353 citations
TL;DR: This review provides a comprehensive account of phytoalexin induction throughout the plant kingdom, with special attention to comparative aspects.
192 citations
TL;DR: The phytoalexin production potential of three American Vitis species and that of three cultivars of Vitis vinifera were evaluated in response to UV-C irradiation, showing that the two major stilbenes accumulated as a response toUV-C elicitation are resveratrol and epsilon-viniferin.
Abstract: The phytoalexin production potential of three American Vitis species and that of three cultivars of Vitis vinifera were evaluated in response to UV-C irradiation. Time course changes in resveratrol, piceid, epsilon-viniferin, and pterostilbene contents were studied within 3 days after a short UV-C irradiation. Results show that the two major stilbenes accumulated as a response to UV-C elicitation are resveratrol and epsilon-viniferin, a resveratrol dehydrodimer, the concentration of both compounds usually reaching quantities >100 microgram/g of fresh weight. In contrast, piceid and pterostilbene were constantly produced in low quantities. Owing to the results obtained, the role of stilbene phytoalexins in the resistance of grapevines to diseases is discussed.
176 citations
TL;DR: It is demonstrated that 3-deoxyanthocyanidin phytoalexins represent major components of resistance to C. sublineolum in sorghum.
151 citations
TL;DR: In this paper, MeJa added during the first half of the exponential growth phase increased the intracellular accumulation of stilbenes, mainly (Z)- and (E)-piceid (3,5,4‘-trihydroxystilbene-3-O-β-glucoside), in strains grown in either maintenance medium or polyphenol inductive medium.
Abstract: Vitis vinifera cells grown in vitro respond to methyl jasmonate (MeJa) with enhancement of phytoalexin accumulation. MeJa added during the first half of the exponential growth phase increased the intracellular accumulation of stilbenes, mainly (Z)- and (E)-piceid (3,5,4‘-trihydroxystilbene-3-O-β-glucoside), in strains grown in either maintenance medium or polyphenol inductive medium. Plant cell cultures were used to produce isotopically (13C) labeled stilbenes by addition of 13C phenylalanine at different time intervals and in various concentrations. Incorporation of 13C phenylalanine into stilbenes was measured by EA-IRMS, and three successive 2-mM phenylalanine additions provided the best result (66%). This allowed production of 13C labeled Vitis vinifera phenolic compounds for investigation of their absorption in humans.
91 citations
TL;DR: The data suggest that in pine the gene product of PST-1 is responsible for both the stress response in seedlings and pinosylvin formation in the heartwood.
Abstract: Young pine seedlings respond to environmental stress by induced synthesis of pinosylvin, a stilbene phytoalexin. Heartwood of pine trees is characterized by a high content of pinosylvin. The formation of pinosylvin from cinnamoyl-CoA and three molecules malonyl-CoA catalysed by pinosylvin synthase is typical of the genus Pinus. Its enzyme activity not detectable in unstressed seedlings is substantially increased upon application of stimuli like UV-light or infection with the phytopathogenic fungus Botrytis cinerea. A genomic DNA library was screened with pinosylvin synthase cDNA pSP-54 as a probe. Ten clones were isolated and grouped into five subclasses according to the size of their introns. After subcloning into plasmid T7T3, four different members of the five gene subclasses were characterized by sequencing. Emphasis was put on isolating various promoters and analyzing and comparing their responsiveness. The amino acid sequences deduced from genes PST-1, PST-2, PST-3 and PST-5 shared an overall identity of more than 95%. In gene PST-5, the putative translation start site ATG was replaced by CTG. While promoter regions near the TATAA box were almost identical PST-1, PST-2 and PST-3, further upstream sequences differed substantially. Differences in promoter strength were analysed both in transgenic tobacco plants and by transient expression in tobacco protoplasts. Constructs used contained the bacterial beta-glucuronidase under the control of the promoters of pine genes PST-1, PST-2 and PST-3. Upon treatment with UV light or fungal elicitor, the promoter of PST-1 showed highest responsiveness and led to tissue-specific expression in vascular bundles. The data suggest that in pine the gene product of PST-1 is responsible for both the stress response in seedlings and pinosylvin formation in the heartwood.
82 citations
TL;DR: Study of degradation of pterostilbene that has just one free hydroxy phenyl group function allowed us to determine the oxidative dimerization process undergone by grapevine phytoalexins after B. cinerea infection.
Abstract: In the interaction between grapevines and Botrytis cinerea, one of the main aspects of pathogenicity is fungal ability to degrade phytoalexins synthesized by the plant in response to infection. Laccase-like stilbene oxidase activity in liquid cultures of B. cinerea has been shown to be related to the decrease of phytoalexin concentrations. Recent research and results presented in this paper determined the chemical structure of a pterostilbene metabolite produced by B. cinerea. Study of degradation of pterostilbene that has just one free hydroxy phenyl group function allowed us to determine the oxidative dimerization process undergone by grapevine phytoalexins after B. cinerea infection. The phytopathological significance of this degradation process in the B. cinerea interaction has also been discussed.
55 citations
TL;DR: In this article, the authors investigated the biosynthesis of oat phytoalexins, avenanthramides, by administering labeled precursors to oat leaf segments treated with the elicitor, penta-N-acetylchitopentaose.
TL;DR: In this article, desoxyhemigossypol (dHG) and hemigossymol (HG), a phyto-alexin, were identified as part of the foliar resistance response to Xanthomonas campestris pv.
TL;DR: The remarkable metabolism of the cruciferous phytoalexin cyclobrassinin by the phytopathogenic root rot and blackleg fungi and the chemistry involved in the structure determination of the intermediates of these three apparently different pathways and their antifungal activities are described.
Abstract: The remarkable metabolism of the cruciferous phytoalexin cyclobrassinin by the phytopathogenic root rot (Rhizoctonia solani Kuhn) and blackleg [Phoma lingam (Tode ex Fr.) Desm., asexual stage of Leptosphaeria maculans (Desm.) Ces. et de Not.] fungi is reported. It was established that R. solani metabolized and detoxified cyclobrassinin via the phytoalexin brassicanal A, which was further transformed into nontoxic products. Detoxification of cyclobrassinin in P. lingam avirulent isolate Unity occurred via the phytoalexin brassilexin, whereas the detoxification in P. lingam virulent isolate BJ 125 occurred via the phytoalexin dioxibrassinin. The chemistry involved in the structure determination of the intermediates of these three apparently different pathways and their antifungal activities are described. In addition, efficient syntheses of both phytoalexins brassicanal A and brassilexin by mimicry of the fungal biotransformation route are reported. Implications of these unprecedented transformations are discussed.
TL;DR: Changes in phy toalexin concentrations and enzyme activity are consistent with the hypothesis that phytoalexins are an essential component in protecting the plant from infection by V. dahliae.
Abstract: Phytoalexin biosynthesis occurred earlier in the resistant cotton cultivar Seabrook Sea Island 12B2 (SBSI) (Gossypium barbadense) than in the susceptible cotton cultivar Rowden (G. hirsutum) after inoculation with a defoliating isolate of the pathogen Verticillium dahliae. This was demonstrated by significantly higher levels of phytoalexins in SBSI 12 h after inoculation. Furthermore, by 48 h after inoculation of SBSI, the phytoalexins hemigossypol and desoxyhemigossypol achieved levels (23.9 and 10.5 microgram/g of fresh tissue, respectively) sufficient to completely inhibit conidial germination. Rowden required 96 h to attain comparable levels. Similarly, the activity of delta-cadinene synthase, a key enzyme required for the biosynthesis of the terpenoid phytoalexins, increased more rapidly in the resistant cotton cultivar than in the susceptible one. The changes in phytoalexin concentrations and enzyme activity are consistent with the hypothesis that phytoalexins are an essential component in protecting the plant from infection by V. dahliae.
TL;DR: Seven triterpenoid phytoalexins were isolated from peel of unripe fruits of nectarine wounded and inoculated with Colletotrichum musae and showed antifungal activity against the fungus mentioned.
01 Jan 1999
TL;DR: Study on natural variation in phytoalexin production and the accumulation of phy toalexins under field conditions will be presented as another means of evaluating the role of these compounds in resistance to pathogens and other pests.
Abstract: Plants resist pathogens with combinations of constitutive and induced defences. Of the induced defences, phytoalexin production has received much attention since the phytoalexin concept was introduced over 50 years ago. However, the specific role of phytoalexins in disease resistance is not clear for the majority of host-parasite systems. Much of the research on phytoalexins has relied on the identification of induced antifungal compounds and correlating their presence with resistance. Although an important first step, more definitive studies are needed. Approaches that use in situ localization and quantification have provided good evidence that phytoalexins can accumulate at the right time, concentration, and location to be effective in resistance. Studies on phytoalexin tolerance in pathogenic fungi have also shown a relationship between virulence and the ability of fungi to detoxify phytoalexins. Use of mutants deficient in phytoalexin synthesis and elucidating biosynthetic pathways provide other approaches to evaluating the role of phytoalexins. These approaches will be illustrated using the Arabidopsis-camalexin system and other selected examples. Studies on natural variation in phytoalexin production and the accumulation of phytoalexins under field conditions will be presented as another means of evaluating the role of these compounds in resistance to pathogens and other pests.
TL;DR: The CA-ACCO gene was strongly expressed under stress conditions but hardly detected in breaker stage pepper fruits in contrast with tomato ripening fruits.
TL;DR: The main mode of action of isomer A appears to be an enhancement of phytoalexin synthesis during blast infection similar to that of WL28325, rather than the inhibition of melanin biosynthesis (MBI mode).
Abstract: Carpropamid {(1RS, 3SR)-2,2-dichloro-N-[1-(4-chlorophenyl) ethyl]-1-ethyl-3-methyl cyclo-propanecarboxamide}, which is considered as a melanin biosynthesis inhibitor, enhanced the accumulation of the phytoalexins momilactone A and sakuranetin in the rice leaves subsequently inoculated with the blast pathogen (Pyricularia oryzae). Carpropamid and its two diastereo-isomers, A(1R,3S) and B(1S,3R), did not stimulate phytoalexin production directly, but they potentiated rice plants to produce the two phytoalexins more rapidly and much amounts in response to blast infection. This phenomenon was also observed in rice leaves treated with WL28325 (2,2-dichloro-3,3-dimethylcyclopropane carboxylic acid), a resistance inducer. The calculation data of the correlation among accumulation of phytoalexins, concentrations of chemicals and biological effects suggested that the correlation pattern of isomer A resembled that of WL28325. The main mode of action of isomer A appears to be an enhancement of phytoalexin synthesis during blast infection (EPAS mode) similar to that of WL28325, rather than the inhibition of melanin biosynthesis (MBI mode). In contrast, the main mode of action of isomer B was found to be MBI, although EPAS probably also contributes to its biological activity. Carpropamid is assumed to control rice blast through a combination of MBI and EPAS activities.
TL;DR: Xanthoarnol was the major compound produced by elicited cells and showed an inhibitory effect on the germination of conidia of the parasitic fungus and is a new phytoalexin described in a plant–fungus interaction.
TL;DR: It was shown that leaves responded by different levels of phytoalexin accumulation after fungal elicitor treatment, and jasmonic acid did not mimic biotic stress by itself, it only increased the response of leaf cells to fungal elicit leading to an activation of coumarin metabolism.
01 Jan 1999
TL;DR: The results strongly support the idea that camalexin does not play a major role in plant resistance to P. syringae infection, although it is involved in resistance to a fungal pathogen.
Abstract: Phytoalexins are low molecular weight antimicrobial compounds that are synthesized in response to pathogen attack. The phytoalexin camalexin, an indole derivative, is produced by Arabidopsis in response to infection with the bacterial pathogen Pseudomonas syringae. The phytoalexin deficient 3 (pad3) mutation, which causes a defect in camalexin pro? duction, has no effect on resistance to P. syringae but compromises resistance to the fungal pathogen Alternaria bras? sicicola. We have now isolated PAD3 by map-based cloning. The predicted PAD3 protein appears to be a cytochrome P450 monooxygenase, similar to those from maize that catalyze synthesis of the indole-derived secondary metabolite 2,4-dihydroxy-1,4-benzoxazin-3-one. The expression of PAD3 is tightly correlated with camalexin synthesis and is reg? ulated by PAD4 and PAD1. On the basis of these findings, we conclude that PAD3 almost certainly encodes an enzyme required for camalexin biosynthesis. Moreover, these results strongly support the idea that camalexin does not play a major role in plant resistance to P. syringae infection, although it is involved in resistance to a fungal pathogen.
01 Jan 1999