B1-phytoprostanes trigger plant defense and detoxification responses.

Phytoprostanes are prostaglandin/jasmonate-like products of nonenzymatic lipid peroxidation that not only occur ubiquitously in healthy plants but also increase in response to oxidative stress. In this work, we show that the two naturally occurring B(1)-phytoprostanes (PPB(1)) regioisomers I and II (each comprising two enantiomers) are short-lived stress metabolites that display a broad spectrum of biological activities. Gene expression analysis of Arabidopsis (Arabidopsis thaliana) cell cultures treated with PPB(1)-I or -II revealed that both regioisomers triggered a massive detoxification and defense response.

The jasmonate-insensitive mutant jin1 shows increased resistance to biotrophic as well as necrotrophic pathogens.

SUMMARY Jasmonic acid and related oxylipin compounds are plant signalling molecules that are involved in the response to pathogens, insects, wounding and ozone. To explore further the role of jasmonates in stress signal transduction, the response of two jasmonate-signalling mutants, jin1 and jin4, to pathogens and ozone was analysed in this study. Upon treatment with the biotrophic bacterial pathogen Pseudomonas syringae, endogenous jasmonate levels increased in jin1 and jin4 similar to wild-type, demonstrating that these mutants are not defective in jasmonate biosynthesis.

Cyclopentenone isoprostanes induced by reactive oxygen species trigger defense gene activation and phytoalexin accumulation in plants.

Lipid peroxidation may be initiated either by lipoxygenases or by reactive oxygen species (ROS). Enzymatic oxidation of alpha-linolenate can result in the biosynthesis of cyclic oxylipins of the jasmonate type while free-radical-catalyzed oxidation of alpha-linolenate may yield several classes of cyclic oxylipins termed phytoprostanes in vivo. Previously, we have shown that one of these classes, the E1-phytoprostanes (PPE1), occurs ubiquitously in plants.

Biosynthesis of 14,15-dehydro-12-oxo-phytodienoic acid and related cyclopentenones via the phytoprostane D(1) pathway.

A novel group of cyclopentenone prostaglandin-like compounds, deoxy phytoprostanes J(1), together with their precursors, phytoprostanes D(1), were identified in tobacco, tomato and Arabidopsis. Previously, it was thought that 14,15-dehydro-12-oxo-phytodienoic acid, a member of the deoxy phytoprostanes J(1) family, is derived from either 12-oxo-phytodienoic acid or diketols via the allene oxide synthase pathway. Results suggest that 14,15-dehydro-12-oxo-phytodienoic acid as well as structurally related cyclopentenones of the chromomoric acid family are synthesized via the phytoprostane D(1) pathway in planta.