Delay of Iris flower senescence by protease inhibitors

Authors

  • Caroline Pak,

    1. Agrotechnology and Food Innovations (A & F), Wageningen University and Research Centre, PO Box 17, 6700 AA Wageningen, the Netherlands
    Search for more papers by this author
  • Wouter G. Van Doorn

    Corresponding author
    1. Agrotechnology and Food Innovations (A & F), Wageningen University and Research Centre, PO Box 17, 6700 AA Wageningen, the Netherlands
      Author for correspondence: Wouter G. van Doorn Tel: +31 317-475105 Fax: +31 317-475347 Email: wouter.vandoorn@wur.nl
    Search for more papers by this author

Author for correspondence: Wouter G. van Doorn Tel: +31 317-475105 Fax: +31 317-475347 Email: wouter.vandoorn@wur.nl

Summary

  • • 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.

Ancillary