title: Changes in ultrastructure, protease and caspase-like activities during flower senescence in Lilium longiflorum.
abstract: The last phase of flower development is senescence during which nutrients are recycled to developing tissues. The ultimate fate of petal cells is cell death. In this study we used the ethylene-insensitive Lilium longiflorum as a model system to characterize Lily flower senescence from the physiological, biochemical and ultrastructural point of view. Lily flower senescence is highly predictable: it starts three days after flower opening, before visible signs of wilting, and ends with the complete wilting of the corolla within 10 days. The earliest events in L. longiflorum senescence include a fall in fresh and dry weight, fragmentation of nuclear DNA and cellular disruption. Mesophyll cell degradation is associated with vacuole permeabilization and rupture. Protein degradation starts later, coincident with the first visible signs of tepal senescence. A fall in total protein is accompanied by a rise in total proteases, and also by a rise of three classes of caspase-like activity with activities against YVAD, DEVD and VEID. The timing of the appearance of these caspase-like activities argues against their involvement in the regulation of the early stages of senescence, but their possible role in the regulation of the final stages of senescence and cell death is discussed.
authors.affiliation: Department of Crop Plant Biology, University of Pisa, Via Mariscoglio 34, 56124 Pisa, Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Battelli
authors.forename: Lara
authors.initials: L
authors.lastname: Lombardi
authors.forename: Hilary J
authors.initials: HJ
authors.lastname: Rogers
authors.forename: Piero
authors.initials: P
authors.lastname: Picciarelli
authors.forename: Roberto
authors.initials: R
authors.lastname: Lorenzi
authors.forename: Nello
authors.initials: N
authors.lastname: Ceccarelli
mesh_terms: D000375:Aging; D001343:Autophagy; D020169:Caspases / Q000032:analysis / Q000378:metabolism*; D035264:Flowers / Q000201:enzymology* / Q000502:physiology / Q000648:ultrastructure; D018506:Gene Expression Regulation, Plant; D027762:Lilium / Q000201:enzymology / Q000502:physiology* / Q000648:ultrastructure; D058503:Mesophyll Cells / Q000502:physiology; D010447:Peptide Hydrolases / Q000032:analysis / Q000378:metabolism*; D010940:Plant Proteins / Q000032:analysis / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D010447:Peptide Hydrolases; D020169:Caspases