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GrainGenes Reference Report: TPJ-199

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Reference	TPJ-199
Title	Allene oxide synthases of barley (Hordeum vulgare cv. Salome): tissue specific regulation in seedling development
Journal	The Plant Journal
Year	2000
Pages	199-213
Author	Maucher H Hause B Feussner I Ziegler J Wasternack C
Abstract	Summary: Allene oxide synthase (AOS) is the first enzyme in the lipoxygenase (LOX) pathway which leads to formation of jasmonic acid (JA). Two full-length cDNAs of AOS designated as AOS1 and AOS2, respectively, were isolated from barley (H. vulgare cv. Salome) leaves, which represent the first AOS clones from a monocotyledonous species. For AOS1, the open reading frame encompasses 1461 bp encoding a polypeptide of 487 amino acids with calculated molecular mass of 53.4 kDa and an isoelectric point of 9.3, whereas the corresponding data of AOS2 are 1443 bp, 480 amino acids, 52.7 kDa and 7.9. Southern blot analysis revealed at least two genes. Despite the lack of a putative chloroplast signal peptide in both sequences, the protein co-purified with chloroplasts and was localized within chloroplasts by immunocytochemical analysis. The barley AOSs, expressed in bacteria as active enzymes, catalyze the dehydration of LOX-derived 9- as well as 13-hydroperoxides of polyenoic fatty acids to the unstable allene oxides. In leaves, AOS mRNA accumulated upon treatment with jasmonates, octadecanoids and metabolizable carbohydrates, but not upon floating on abscisic acid, NaCl, Nasalicylate or infection with powdery mildew. In developing seedlings, AOS mRNA strongly accumulated in the scutellar nodule, but less in the leaf base. Both tissues exhibited elevated JA levels. In situ hybridizations revealed the preferential occurrence of AOS mRNA in parenchymatic cells surrounding the vascular bundles of the scutellar nodule and in the young convoluted leaves as well as within the first internode. The properties of both barley AOSs, their up-regulation of their mRNAs and their tissue specific expression suggest a role during seedling development and jasmonate biosynthesis
Keyword	[ Hide all but 1 of 55 ] abscisic acid allene amino acid amino acid sequence bacteria barley biosynthesis carbohydrate cdna cell chloroplast complementary dna dehydration dna hybridization enzyme enzyme activity experimental infections fatty fatty acids gene gene expression histochemistry hordeum vulgare hybridization immunocytochemistry in situ in situ hybridization infection isoelectric point jasmonic acid lipoxygenase molecular weight mrna nacl open reading frame parenchyma peptide plant development plant tissues polypeptide powdery mildew reading frame regulation salicylic acid seedling development sequence signal signal peptide sodium chloride stearic acid synthase tissue tissue specific expression transgenics vascular bundles

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