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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.

Immunity of plants triggered by pathogen-associated molecular patterns (PAMPs) is based on the execution of an evolutionarily conserved defense response that includes the accumulation of pathogenesis-related (PR) proteins as well as multiple other defenses. The most abundant PR transcript of barley (Hordeum vulgare) leaf epidermis attacked by the powdery mildew fungus Blumeria graminis f. sp hordei encodes the germin-like protein GER4, which has superoxide dismutase activity and functions in PAMP-triggered immunity. Here, we show that barley GER4 is encoded by a dense cluster of tandemly duplicated genes (GER4a-h) that underwent several cycles of duplication. The genomic organization of the GER4 locus also provides evidence for repeated gene birth and death cycles. The GER4 promoters contain multiple WRKY factor binding sites (W-boxes) preferentially located in promoter fragments that were exchanged between subfamily members by gene conversion. Mutational analysis of TATA-box proximal W-boxes used GER4c promoter-β-glucuronidase fusions to reveal their enhancing effects and functional redundancy on pathogen-induced promoter activity. The data suggest enhanced transcript dosage as an evolutionary driving force for the local expansion and functional redundancy of the GER4 locus. In addition, the GER4c promoter provides a tool to study signal transduction of PAMP-triggered immunity and to engineer strictly localized and pathogen-regulated disease resistance in transgenic cereal crops.

\"Helmut Maucher\" is cool on assuming there must always be a global strategy, but supports sensible acquisition strategy and sympathetic product and sector development

Immature scutella of barley were transformed with cDNA coding for a 13-lipoxygenase of barley (LOX-100) via particle bombardment. Regenerated plants were tested by PAT-assay, Western-analysis and PCR-screening. Immunocytochemical assay of T0 plants showed expression of the LOX cDNA both in the chloroplasts and in the cytosol, depending on the presence of the chloroplast signal peptide sequences in the cDNA. A few transgenic plants containing higher amounts of LOX-derived products have been found. These are the candidates for further analysis concerning pathogen resistance.