Characterization of a Novel Lipoxygenase-Independent Senescence Mechanism in Alstroemeria peruviana Floral Tissue

Michael K. Leverentz , Carol Wagstaff , Hilary J. Rogers , Anthony D. Stead , Usawadee Chanasut , Helena Silkowski , Brian Thomas , Heiko Weichert , Ivo Feussner , and Gareth Griffiths ^*

Department of Plant Genetics and Biotechnology, Horticulture Research International, Wellesbourne, Warwickshire CV35 9EF, United Kingdom (M.K.L., H.S., B.T., G.G.); Cardiff School of Biosciences, Cardiff University, P.O. Box 915, Cardiff CF10 3TL, United Kingdom (C.W., H.J.R.); School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey TW 20 0EX, United Kingdom (A.D.S., U.C.); and Institute of Plant Genetics and Crop Plant Research, D ${ndash}$ 06466 Gatersleben, Germany (H.W., I.F.)

^* Corresponding author; email: gareth.griffiths{at}hri.ac.uk.

The role of lipoxygenase (lox) in senescence of Alstroemeria peruviana flowers was investigated using a combination of in vitro assays and chemical profiling of the lipid oxidation products generated. Phospholipids and galactolipids were extensively degraded during senescence in both sepals and petals and the ratio of saturated/unsaturated fatty acids increased. Lox protein levels and enzymatic activity declined markedly after flower opening. Stereochemical analysis of lox products showed that 13-lox was the major activity present in both floral tissues and high levels of 13-keto fatty acids were also synthesized. Lipid hydroperoxides accumulated in sepals, but not in petals, and sepals also had a higher chlorophyll to carotenoid ratio that favors photooxidation of lipids. Loss of membrane semipermeability was coincident for both tissue types and was chronologically separated from lox activity that had declined by over 80% at the onset of electrolyte leakage. Thus, loss of membrane function was not related to lox activity or accumulation of lipid hydroperoxides per se and differs in these respects from other ethylene-insensitive floral tissues representing a novel pattern of flower senescence.

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