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Abstract

In biosynthesis of octadecanoids and jasmonate (JA), the naturally occurring enantiomer is established in a step catalysed by the gene cloned recently from tomato as a single-copy gene (Ziegler et al., 2000). Based on sequence homology, four full-length cDNAs were isolated from Arabidopsis thaliana ecotype Columbia coding for proteins with AOC activity. The expression of AOC genes was transiently and differentially up-regulated upon wounding both locally and systemically and was induced by JA treatment. In contrast, AOC protein appeared at constitutively high basal levels and was slightly increased by the treatments. Immunohistochemical analyses revealed abundant occurrence of AOC protein as well as of the preceding enzymes in octadecanoid biosynthesis, lipoxygenase (LOX) and allene oxide synthase (AOS), in fully developed tissues, but much less so in 7-day old leaf tissues. Metabolic profiling data of free and esterified polyunsaturated fatty acids and lipid peroxidation products including JA and octadecanoids in wild-type leaves and the jasmonate-deficient mutant OPDA reductase 3 (opr3) revealed preferential activity of the AOS branch within the LOX pathway. 13-LOX products occurred predominantly as esterified derivatives, and all 13-hydroperoxy derivatives were below the detection limits. There was a constitutive high level of free 12-oxo-phytodienoic acid (OPDA) in untreated wild-type and opr3 leaves, but an undetectable-expression of AOC. Upon wounding opr3 leaves exhibited only low expression of AOC, wounded wild-type leaves, however, accumulated JA and AOC mRNA. These and further data suggest regulation of JA biosynthesis by OPDA compartmentalization and a positive feedback by JA during leaf development.

Ethylene-mediated cross-talk between calcium-dependent protein kinase and MAPK signaling controls stress responses in plants

“…The spreading behavior of the VK-dependent HR beyond the initial wounding sites indicates the presence of a systemic signal. The VK-dependent accumulation of hydrogen peroxide occurred predominantly adjacent to the vasculature, where, interestingly, the machinery for JA synthesis has also been localized (26). This correlation suggests that, during pathogen defense or stress responses, NtCDPK2 may indirectly be involved in the generation of a systemic signal, which could be found among the classes of enzymatically and nonenzymatically derived oxygenated fatty acid molecules, such as oxylipins or phytoprostanes (38).…”

“…JA and OPDA levels were determined upon derivatization to JA-and dn-OPDA pentafluoro-benzyl esters as described in ref. 26. For SA determination, leaf tissue from three independent plants (0.5 g of fresh weight each) per sample was harvested before and after the flooding stimulus.…”

New Functions of the Thylakoid Membrane Proteome of Arabidopsis thaliana Revealed by a Simple, Fast, and Versatile Fractionation Strategy

“…They were all identified multiple times in the TPP fractions, often with very high probability-based Mowse scores, suggesting that they are quite abundant. Allene-oxide synthase is a single copy gene, whereas four genes encode allene-oxide cyclase (52). Interestingly, we identified only two of the four paralogs of allene-oxide cyclase; one form, AOC2 (At3g25770), was identified Ͼ30 times, with high probability-based Mowse scores, suggesting the highest abundance of this particular paralog.…”

Oxylipin Profiling of the Hypersensitive Response inArabidopsis thaliana

“…Lipid Extraction and Oxylipin Profiling-Lipids were extracted by hexane/isopropyl alcohol extraction and partitioned against an aqueous phase (22). For analysis of free oxylipins, known amounts of deuterated JA, OPDA, and 13␥-HOT were included in the extraction as internal standards.…”