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  • 1
    ISSN: 1432-2048
    Keywords: Aspirin ; Gene expression ; Jasmonic acid ; Lycopersicon ; Proteinase inhibitor II ; Wounding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Jasmonic acid (JA) and its methyl ester, like mechanical wounding, strongly induce accumulation of proteinase inhibitor II (Pin2) in tomato and potato leaves. In plants, JA is synthesized from α-linolenic acid by a lipoxygenase (LOX)-mediated oxygenation leading to 13-hydroxyperoxylinolenic acid (13-HPLA) which is then subsequently transformed to JA by the action of hydroperoxide-dehydrase activity and additional modification steps. Both the chemical structure as well as the biosynthetic pathway of JA resemble those of the mammalian eicosanoids (prostaglandins and leukotrienes) which are derived from LOX-and cyclooxygenase (COX)-mediated reactions. To assess the role of endogenous JA in the wound response, detached tomato (Lycopersicon esculentum Mill.) leaves were supplied with different LOX and COX inhibitors and the expression of the wound-induced genes for Pin2 (Pin2), cathepsin D inhibitor (Cdi) and threonine deaminase (Td) was analyzed. Lipoxygenase inhibitors as well as some COX inhibitors blocked the wound-induced accumulation of Pin2, Cdi and Td mRNA. Quantitation of endogenous levels of JA showed that aspirin blocks the increase of this phytohormone normally observed as a result of wounding. Linolenic acid and 13-HPLA do not induce the expression of Pin2, Cdi and Td in the presence of aspirin. However, 12-oxo-phytodienoic acid and jasmonic acid are able to overcome the inhibitory effect of this substance. These results strongly indicate that aspirin prevents wound-induced gene activation by inhibiting the hydroxyperoxide-dehydrase activity that mediates the conversion of 13-HPLA to 12-oxo-phytodienoic acid.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2048
    Keywords: Bryonia ; Jasmonic acid ; Methyljasmonate ; α-Linolenic acid ; Tendril coiling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A coiling-inducing factor was isolated from tendrils of Bryonia dioica Jacq. and identified by infrared, 1H-, 13C-nuclear magnetic resonance and mass spectrometry as α-linolenic acid. When applied to detached tendrils, exogenous α-linolenic acid, but not linoleic acid or oleic acid, induced tendril coiling. Further investigations showed that metabolites of α-linolenic acid, jasmonic acid and, even more so, methyljasmonate, are highly effective inducers of tendril coiling in B. dioica. Methyljasmonate was most active when administered by air and, in atmospheric concentrations as low as 40–80 nM, induced a full free-coiling response with kinetics similar to mechanical stimulation. Even atmospheric levels as low as 4–5 nM methyljasmonate were still found to be significantly active. Methyljasmonate could be one of the endogenous chemical signals produced in mechanically stimulated parts of a tendril and, being highly volatile, act as a diffusible gaseous mediator spreading through the intracellular spaces to trigger free coiling of tendrils.
    Type of Medium: Electronic Resource
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