Lipoxygenase-mediated production of fatty acid hydroperoxides is a specific signature of the hypersensitive reaction in plants
ABSTRACT Lipoxygenase (LOX)-dependent massive production of (9S) fatty acid hydroperoxides was previously observed in cryptogein-elicited tobacco leaves and proposed as being an actor of cell death during the hypersensitive reaction (HR). In this work, we have further investigated the occurrence of this metabolism for biotic, compatible and incompatible interactions in tobacco, and also in Arabidopsis thaliana. Our methodology, based on metabolite analysis (isomer distribution and chirality), is sufficient to assess for the induction of a LOX metabolism. In both plants, a (13S) oxylipin metabolism is initially operating in control leaves. In tobacco, the (9S) LOX-dependent oxylipin metabolism was shown to be induced by tobacco mosaic virus and an avirulent bacterial strain of Ralstonia solanacearum. In Arabidopsis, accumulation of the oxylipin metabolites in leaves was also observed in response to harpin, and during different incompatible interactions. However, in the latter model, the metabolites are mainly (13S), suggesting the involvement of a specific (13S) LOX. In all cases studied so far, accumulation of the oxylipin metabolites is correlated with HR cell death and is not observed during compatible interactions. In many plant species, LOX transcript accumulation precedes, and LOX activity correlates, the induction of the HR symptoms. Thus, accumulation of the oxylipin metabolites can be considered as a marker of HR cell death in plant–pathogen interactions. Both 9 or 13 oxylipin metabolism can be apparently activated, depending on the plant species.
Article: Oxylipin biosynthesis genes positively regulate PCD during compatible infections by the synergistic pair Potato virus X-Potato virus Y and by Tomato spotted wilt virus.[show abstract] [hide abstract]
ABSTRACT: One of the most severe symptoms caused by compatible plant-virus interactions is systemic necrosis, which shares common attributes with the hypersensitive response to incompatible pathogens. Although several studies have identified viral symptom determinants responsible for systemic necrosis, mechanistic models of how they contribute to necrosis in infected plants remain scarce. Here, we examined the involvement of different branches of the oxylipin biosynthesis pathway in the systemic necrosis response caused by either the synergistic interaction of Potato virus X (PVX) with Potato virus Y (PVY) or by Tomato spotted wilt virus (TSWV) in Nicotiana benthamiana. Silencing either 9-lipoxygenase (LOX), 13-LOX, or α-dioxygenase-1 (α-DOX-1) attenuated the programmed cell death (PCD)-associated symptoms caused by infection with either PVX-PVY or TSWV. In contrast, silencing of the jasmonic acid perception gene, COI1, expedited cell death during infection with compatible viruses. This correlated with an enhanced expression of oxylipin biosynthesis genes and dioxygenase activity in PVX-PVY infected plants. Moreover, the Arabidopsis thaliana double lox1 α-dox-1 mutant became less susceptible to TSWV infection. We conclude that oxylipin metabolism is a critical component that positively regulates the process of PCD during compatible plant-virus interactions but does not play a role in restraining virus accumulation in planta.Journal of Virology 03/2013; · 5.40 Impact Factor
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ABSTRACT: Oxylipins generated by the lipoxygenase (LOX) pathway play an important role in plant defense against biotic and abiotic stress. In chitosan-treated Adelostemma gracillimum seedlings, obvious accumulation of 9-LOX-derived oxylipins, namely 9,10,11-trihydroxy-12-octadecenoic acid, was detected. Using degenerate primers, a LOX-specific fragment putatively encoding LOX was obtained by RT-PCR, and a 2.9-kb full-length cDNA named AgLOX1 was isolated by RACE from chitosan-induced A. gracillimum seedlings. Genomic Southern analysis implied that there was only one copy of AgLOX1 in the A. gracillimum genome. AgLOX1 was expressed in Escherichia coli and the recombinant protein was partially purified. The enzyme converted linoleic and linolenic acids almost exclusively to their 9-hydroperoxides. AgLOX1 encoded a 9-lipoxygenase. Northern blot analysis indicated that chitosan-induced AgLOX1 transcript accumulation peaked at 8 h after initiation of treatment, whereas trihydroxy derivatives accumulation was highest at 24 h after elicitation. Results showed that chitosan-induced AgLOX1 encoded a 9-lipoxygenase potentially involved in the defense response through 9-LOX pathway leading to biosynthesis of antimicrobial compounds in A. gracillimum seedlings.International Journal of Molecular Sciences 01/2012; 13(1):540-51. · 2.60 Impact Factor