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1.
J Chem Ecol ; 37(7): 677-86, 2011 Jul.
Article in English | MEDLINE | ID: mdl-21671082

ABSTRACT

The red alga Gracilaria chilensis is commercially farmed for the production of agar hydrocolloids, but some susceptible algae in farms suffer from intense epiphyte growth. We investigated the induced chemical defense response of G. chilensis against epiphytes and demonstrated that an extract of an epiphyte-challenged alga can trigger a defense response. The hormonally active metabolites were purified by RP-HPLC. Treatment with the extract or the purified fraction changed the chemical profile of the alga and increased resistance against epiphyte spores. Semi-quantitative RT-PCR and enzyme assays demonstrated that this metabolic response occurs after an increase in lipoxygenase and phospholipase A2 activity. Although this suggests the involvement of regulatory oxylipins, neither jasmonic acid nor the algal metabolite prostaglandin E2 triggers comparable defense responses.


Subject(s)
Gracilaria/enzymology , Lipoxygenase/metabolism , Phospholipases A/metabolism , Plant Immunity/physiology , Cyclopentanes/metabolism , Dinoprostone/metabolism , Lipoxygenase/genetics , Oxylipins/metabolism , Phospholipases A/genetics , Plant Growth Regulators/metabolism , Reverse Transcriptase Polymerase Chain Reaction , Up-Regulation/physiology
2.
J Chem Ecol ; 34(5): 601-4, 2008 May.
Article in English | MEDLINE | ID: mdl-18408973

ABSTRACT

Herbivore-induced volatile organic compounds (VOCs) are widely appreciated as an indirect defense mechanism since carnivorous arthropods use VOCs as cues for host localization and then attack herbivores. Another function of VOCs is plant-plant signaling. That VOCs elicit defensive responses in neighboring plants has been reported from various species, and different compounds have been found to be active. In order to search for a structural motif that characterizes active VOCs, we used lima bean (Phaseolus lunatus), which responds to VOCs released from damaged plants with an increased secretion of extrafloral nectar (EFN). We exposed lima bean to (Z)-3-hexenyl acetate, a substance naturally released from damaged lima bean and known to induce EFN secretion, and to several structurally related compounds. (E)-3-hexenyl acetate, (E)-2-hexenyl acetate, 5-hexenyl acetate, (Z)-3-hexenylisovalerate, and (Z)-3-hexenylbutyrate all elicited significant increases in EFN secretion, demonstrating that neither the (Z)-configuration nor the position of the double-bond nor the size of the acid moiety are critical for the EFN-inducing effect. Our result is not consistent with previous concepts that postulate reactive electrophile species (Michael-acceptor-systems) for defense-induction in Arabidopsis. Instead, we postulate that physicochemical processes, including interactions with odorant binding proteins and resulting in changes in transmembrane potentials, can underlie VOCs-mediated signaling processes.


Subject(s)
Phaseolus/metabolism , Phaseolus/physiology , Signal Transduction , Volatilization
3.
Plant Signal Behav ; 3(11): 1005-7, 2008 Nov.
Article in English | MEDLINE | ID: mdl-19704435

ABSTRACT

Studies on direct and indirect defenses of lima bean (Phaseolus lunatus L.) revealed a quantitative trade-off between cyanogenesis and the total quantitative release of herbivore-induced volatile organic compounds (VOCs). In this addendum we focus on the qualitative variability in the VOC bouquets. We found intraspecific and ontogenetic variation. Five out of eleven lima bean accessions lacked particular VOCs in the bouquets released from secondary and/or primary leaves. These compounds (cis-3-hexenyl acetate, methyl salicylate and methyl jasmonate) can induce and prime indirect defenses in neighboring plants. Thus, the variability in VOC quality as described here might have substantial effects on plant-plant communication.

4.
Chembiochem ; 7(3): 457-62, 2006 Mar.
Article in English | MEDLINE | ID: mdl-16482501

ABSTRACT

We investigated the wound response of the commercially important red alga, Gracilaria chilensis, in order to obtain insight into its interaction with epiphytic pests. After wounding, the host releases free fatty acids as well as the hydroxylated eicosanoids, 8R-hydroxy eicosatetraenoic acid (8-HETE) and 7S,8R-dihydroxy eicosatetraenoic acid (7,8-di-HETE). While the release of free arachidonic acid and subsequent formation of 8-HETE is controlled by phospholipase A, 7,8-di-HETE production is independent of this lipase. This dihydroxylated fatty acid might be directly released from galactolipids. Physiologically relevant concentrations of oxylipins reduced spore settlement of Acrochaetium sp. (Rhodophyta, Acrochaetiaceae) and suppressed the development of hapteria in Ceramium rubrum (Rhodophyta, Ceramiaceae) when these model epiphytes were exposed to artificial surfaces that contained 8-HETE or 7,8-di-HETE. Thus, the immediate release of oxylipins can be seen as G. chilensis defence against epiphytes.


Subject(s)
Carboxylic Ester Hydrolases/metabolism , Phospholipases/metabolism , Rhodophyta/physiology , Chromatography, Thin Layer , Eicosanoids/metabolism , Gas Chromatography-Mass Spectrometry , Magnetic Resonance Spectroscopy , Organic Chemicals/metabolism , Rhodophyta/enzymology
5.
J Nat Prod ; 68(9): 1397-9, 2005 Sep.
Article in English | MEDLINE | ID: mdl-16180822

ABSTRACT

From Penicillium janczewskii, obtained from a marine sample, two new diastereomeric quinolinones, 3S,4R-dihydroxy-4-(4'-methoxyphenyl)-3,4-dihydro-2(1H)-quinolinone (1) and 3R,4R-dihydroxy-4-(4'-methoxyphenyl)-3,4-dihydro-2(1H)-quinolinone (2), were identified, along with two known alkaloids, peniprequinolone (3) and 3-methoxy-4-hydroxy-4-(4'-methoxyphenyl)-3,4-dihydro-2(1H)-quinolinone (4). Cytotoxicity testing on eight tumor cell lines revealed a moderate specificity of 2 on SKOV-3 cells.


Subject(s)
Alkaloids/isolation & purification , Antineoplastic Agents/isolation & purification , Penicillium/chemistry , Quinolones/isolation & purification , Alkaloids/chemistry , Alkaloids/pharmacology , Antineoplastic Agents/chemistry , Antineoplastic Agents/pharmacology , Drug Screening Assays, Antitumor , Humans , Marine Biology , Molecular Structure , North Sea , Quinolones/chemistry , Quinolones/pharmacology , Stereoisomerism , Tumor Cells, Cultured
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