Topic
Phytoalexin
About: Phytoalexin is a research topic. Over the lifetime, 1161 publications have been published within this topic receiving 63405 citations. The topic is also known as: phytoalexins.
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TL;DR: Inorganic phosphate is discussed as a signal transmitter inducing part of the plant defense responses when inorganic phosphate was applied endogenously to pea tissues but phytoalexin production was not.
Abstract: When inorganic phosphate, a common and essential element for organisms, was applied endogenously, a rejection reaction and superoxide generation were induced in pea tissues but phytoalexin production was not. Phosphate-induced superoxide generation was sensitive to cycloheximide (CHX) and salicylhydroxamic acid (SHAM), indicating that part of the generation was dependent upon the expression of peroxidase gene(s). Peroxidases (POXs) are well known not only to scavenge hydrogen peroxide with phenolics but also to generate superoxide via NADH oxidation in the presence of p-coumaric acid and manganese ion. We cloned five pea POX cDNAs that are predicted to be located outside of the cells. The accumulation of five POX mRNAs, NTPase mRNA, and phenylalanine ammonia-lyase mRNA was measured by semiquantitative reverse transcription-polymerase chain reaction. The expression of the five POX genes was induced by a fungal elicitor. On the other hand, inorganic phosphate induced the accumulation of POX11, POX14, and POX21 mRNAs but not of POX13, POX29, and PsPAL1 mRNAs within 1–3 h after treatment of pea seedlings. In view of these findings, we discuss inorganic phosphate as a signal transmitter inducing part of the plant defense responses.
22 citations
TL;DR: Three Sclerotinia and Botrytis spp.
Abstract: The pathogenicity to red clover of three Sclerotinia spp. and three Botrytis spp. was compared with their sensitivity to, and ability to degrade, the clover phytoalexins maackiain and medicarpin. Sclerotinia fruticola formed no lesions at all, whereas S. fructigena and Botrytis allii formed flecks under the inoculation drop. B. cinerea and B. fabae formed limited lesions slightly larger than the inoculation drop, and S. trifoliorum formed spreading lesions. In 24 h, S. trifoliorum and B. cinerea degraded both phytoalexins in vitro to less inhibitory hydroxylated derivatives. B. fabae also degraded the phytoalexins but to different products. The other Sclerotinia and Botrytis spp. did so little or not at all. In lesions caused by S. trifoliorum and B. cinerea in clover leaves, the same phytoalexin degradation products were detected as in vitro . S. trifoliorum degraded at a faster rate than B. cinerea in vitro , and in vivo S. trifoliorum was apparently able to metabolize medicarpin and maackiain at a sufficient rate to reduce their concentrations to sub-inhibitory levels. B. cinerea was less able to do so, so that high phytoalexin concentrations were reached in spite of some degradation by the fungus. Following inoculation with S. fructigena, S. fructicola and B. allii , high phytoalexin concentrations were reached in tissue and in diffusates and no degradation products were detected. These three fungi were more sensitive to the phytoalexins with respect to mycelial growth. The oxygen uptake of S. fructicola was also more strongly inhibited by maackiain than that of S. trifoliorum or B. cinerea .
22 citations
Journal Article•
TL;DR: Differences in the cell wall polysaccharide composition of Alibertia myrcifolia and Rudgea jasminoides leaves are reported on to discuss the possible involvement of these pecticpolysaccharides with the capacity of elicitation of phytoalexin in R. jasmine and not in A. myRCifolia.
Abstract: Previous analysis of phytoalexin induction in tropical Rubiaceae revealed that species of Rudgea are capable of synthesizing phytoalexins in response to fungal inducers whereas species of Alibertia showed negative phytoalexin response even when different fungi were used. In the present work we report on differences in the cell wall polysaccharide composition of Alibertia myrcifolia and Rudgea jasminoides leaves. The cell walls of the phytoalexin-producing species R. jasminoides were more labile to Driselase and endopolygalacturonase treatment and contained higher relative amounts of pectins which were richer in acidic polysaccharides than the cell walls of A. myrcifolia. In contrast, a considerably higher proportion of arabinose was detected in pectic polysaccharides of A. myrcifolia. The results are discussed in terms of the possible involvement of these pectic polysaccharides with the capacity of elicitation of phytoalexin in R. jasminoides and not in A. myrcifolia. Additional index terms: Alibertia myrcifolia, hemicelluloses, pectins, Rudgea jasminoides.
22 citations
TL;DR: The elicitation of precursor compounds in the pathosystem A. alternata–tomato was more associated with the infection process than with the chitosan application, and other compounds such as alkenes, fatty acids and vitamin E whose antimicrobial effects have been reported were detected.
22 citations
TL;DR: Activity of the O‐methyltransferase was not found in fresh carrot roots but increased when they were treated with either type of elicitor in parallel with the increase in 6‐methoxymellein content.
22 citations