title: Delay of Iris flower senescence by protease inhibitors.
abstract: Visible senescence of the flag tepals in Iris x hollandica (cv. Blue Magic) was preceded by a large increase in endoprotease activity. Just before visible senescence about half of total endoprotease activity was apparently due to cysteine proteases, somewhat less than half to serine proteases, with a minor role of metalloproteases. Treatment of isolated tepals with the purported serine protease inhibitors AEBSF [4-(2-aminoethyl)-benzenesulfonyl fluoride] or DFP (diisopropyl-fluorophosphate) prevented the increase in endoprotease activity and considerably delayed or prevented the normal senescence symptoms. The specific cysteine protease-specific E-64d reduced maximum endoprotease activity by 30%, but had no effect on the time to visible senescence. Zinc chloride and aprotinin reduced maximum endoprotease activity by c. 50 and 40%, respectively, and slightly delayed visible senescence. A proteasome inhibitor (Z-leu-leu-Nva-H) slightly delayed tepal senescence, which indicates that protein degradation in the proteasome may play a role in induction of the visible senescence symptoms. It is concluded that visible senescence is preceded by large-scale protein degradation, which is apparently mainly due to cysteine- and serine protease activity, and that two (unspecific) inhibitors of serine proteases considerably delay the senescence symptoms.
authors.affiliation: Agrotechnology and Food Innovations (A & F), Wageningen University and Research Centre, PO Box 17, 6700 AA Wageningen, the Netherlands.
authors.forename: Caroline
authors.initials: C
authors.lastname: Pak
authors.forename: Wouter G
authors.initials: WG
authors.lastname: van Doorn
mesh_terms: D035264:Flowers / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development; D031323:Iris Plant / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development; D010447:Peptide Hydrolases / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism; D011480:Protease Inhibitors / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D010940:Plant Proteins; D011480:Protease Inhibitors; D010447:Peptide Hydrolases