title: Enzymes of jasmonate biosynthesis occur in tomato sieve elements.
abstract: The allene oxide cyclase (AOC) is a plastid-located enzyme in the biosynthesis of the signaling compound jasmonic acid (JA). In tomato, AOC occurs specifically in ovules and vascular bundles [Hause et al. (2000) Plant J. 24; 113]. Immunocytological analysis of longitudinal sections of petioles and flower stalks revealed the occurrence of AOC in companion cells (CC) and sieve elements (SE). Electron microscopic analysis led to the conclusion that the AOC-containing structures of SE are plastids. AOC was not detected in SE of 35S::AOCantisense plants. The enzymes preceding AOC in JA biosynthesis, the allene oxide synthase (AOS) and the lipoxygenase, were also detected in SE. In situ hybridization showed that the SE are free of AOC-mRNA suggesting AOC protein traffic from CC to SE via plasmodesmata. A control by in situ hybridization of AOS mRNA coding for a protein with a size above the exclusion limit of plasmodesmata indicated mRNA in CC and SE. The data suggest that SE carry the capacity to form 12-oxo-phytodienoic acid, the unique precursor of JA. Together with preferential generation of JA in vascular bundles [Stenzel et al. (2003) Plant J. 33: 577], the data support a role of JA in systemic wound signaling.
authors.affiliation: Department of Secondary Product Metabolism, Institute for Plant Biochemistry, Weinberg 3, D-06120 Halle, Germany.
authors.forename: Bettina
authors.initials: B
authors.lastname: Hause
authors.forename: Gerd
authors.initials: G
authors.lastname: Hause
authors.forename: Claudia
authors.initials: C
authors.lastname: Kutter
authors.forename: Otto
authors.initials: O
authors.lastname: Miersch
authors.forename: Claus
authors.initials: C
authors.lastname: Wasternack
mesh_terms: D003517:Cyclopentanes / Q000378:metabolism*; D005231:Fatty Acids, Unsaturated / Q000096:biosynthesis; D035264:Flowers / Q000201:enzymology* / Q000648:ultrastructure; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D007150:Immunohistochemistry; D019746:Intramolecular Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D008084:Lipoxygenase / Q000378:metabolism; D018551:Solanum lycopersicum / Q000201:enzymology* / Q000648:ultrastructure; D008854:Microscopy, Electron; D054883:Oxylipins; D018547:Plant Stems / Q000201:enzymology* / Q000648:ultrastructure; D018087:Plastids / Q000201:enzymology* / Q000648:ultrastructure; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D014945:Wound Healing / Q000502:physiology
chemical_list: D003517:Cyclopentanes; D005231:Fatty Acids, Unsaturated; D054883:Oxylipins; D012333:RNA, Messenger; C025999:12-oxophytodienoic acid; C011006:jasmonic acid; D008084:Lipoxygenase; D019746:Intramolecular Oxidoreductases; C021377:hydroperoxide isomerase