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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01 Jan 1991
TL;DR: An extracellular glycoprotein of 42 kDa is purified from the culture filtrate of the soybean pathogen Phytophthora megasperma f.
Abstract: Plants respond to pathogen attack by rapid activation of defense genes. In selected experimental systems, the transcription of these genes is also induced when cultured plant cells or protoplasts are treated with elicitors. We have purified an extracellular glycoprotein of 42 kDa from the culture filtrate of the soybean pathogen Phytophthora megasperma f. sp. glycinea (Pmg), which is a potent elicitor of phytoalexin accumulation and defense gene activation in parsley (1Petroselinum crispum) cells and protoplasts. Reversible binding of the 25I-labelled glycoprotein to microsomes and protoplasts indicates the presence of specific binding sites on the parsley plasma membrane. The transduction of the elicitor signal from the cell surface to the nucleus was found to involve a rapid and transient uptake of Ca2+, alkalization of the culture medium and effluxes of K+ and C1-. These ion fluxes probably result from opening of elicitor-responsive ion channels, as indicated by preliminary results from patch-clamp analysis of parsley protoplasts in the presence of pure glycoprotein elicitor. Omission of Ca2+ from the culture medium substantially reduced the elicitor-induced transcription rates of plant defense genes. Treatment of cultured parsley cells or protoplasts with amphotericin B resulted in ion fluxes and defense gene activation similar to those elicited by the crude Pmg elicitor. The callose elicitors chitosan and digitonin, however, induced ion fluxes of different intensities, activated only some defense genes, and did not stimulate the synthesis of phytoalexins at concentrations optimal for elicitation of callose formation.
26 citations
TL;DR: It is shown that gerbera plants transformed with the gene for 2PS in an antisense orientation and unable to synthesise gerberin and parasorboside are susceptible to Botrytis cinerea infection.
Abstract: A previously isolated cDNA molecule from Gerbera hybrida (Asteraceae) codes for a new chalcone synthase-like polyketide synthase, 2-pyrone synthase (2PS). 2PS is able to synthesise 4-hydroxy-6-methyl-2-pyrone (triacetolactone), a putative precursor for gerberin and parasorboside, two abundant glucosides in gerbera. In this study, we show that gerbera plants transformed with the gene for 2PS in an antisense orientation and unable to synthesise gerberin and parasorboside are susceptible to Botrytis cinerea infection. In addition to the preformed glucosides, the transgenic plants also lack several compounds that are induced in control plants when infected with the mould. Some of these induced substances are effective in inhibiting fungal growth both in vitro and in vivo. Two of the phytoalexins were identified as the aglycones of gerberin and trans-parasorboside. The third phytoalexin is a rare coumarin, 4-hydroxy-5-methylcoumarin; however, it is typical of many plants of the sunflower family Asteraceae. The coumarin cannot be structurally derived from either gerberin or parasorboside, but may be derived from a related polyketide intermediate.
26 citations
TL;DR: Inoculation of white cabbage heads with Pseudomonas cichorii resulted in induction of a new phytoalexin, 4-methoxybrassinin, whose structure was elucidated on the basis of spectroscopic methods.
26 citations
TL;DR: Semi-quantitative RT-PCR revealed that the mRNA was expressed in all tissues tested and was not affected by CuCl2, jasmonic acid or UV treatment, and the enzyme also methylated flavonoids which have two adjacent hydroxyl groups in the B ring.
Abstract: A putative O-methyltransferase cDNA was cloned from UV-irradiated rice leaves based on an amino acid sequence reported as that of naringenin 7-O-methyltransferase, which is involved in the biosynthesis of a rice phytoalexin, sakuranetin. However, the recombinant protein (approximately 41 kDa) expressed in Escherichia coli showed not naringenin 7-O-methyltransferase activity but caffeic acid 3-O-methyltransferase activity. Semi-quantitative RT-PCR revealed that the mRNA was expressed in all tissues tested and was not affected by CuCl2, jasmonic acid or UV treatment. The enzyme also methylated flavonoids which have two adjacent hydroxyl groups in the B ring. © Pesticide Science Society of Japan
26 citations
TL;DR: Wyerone and wyerone acid measured using HPLC are the two main phytoalexins accumulated in response to infection in leaves, and the amounts of unsaturated wyer one derivatives were always higher than their dihydro analogues.
26 citations