Floral senescence: identification and characterization of different patterns of proteolytic activities in Iris oncocyclus and Lisianthus cut flowers.
Philosoph-Hadas S., Friedman H., Lers A., Kochaneck B., Halevy A.H., Meir S.
5th International Postharvest Symposium . Volume of Abstract . Verona, Italy 6-11 June 2004. page 34
2004
บทคัดย่อ
Floral senescence: identification and characterization of different patterns of proteolytic activities in Iris oncocyclus and Lisianthus cut flowers.
Proteolysis seems to be a dominant process in flower senescence, involved in programmed cell death (PCD).Several petal development-induced proteases operating during flower opening and senescence were visualized and characterized in
Iris oncocyclus and Lisianthus (
Eustoma grandiflorum) cut flowers.Iris flower senescence was associated with a decline in petal fresh and dry weight and protein content, and an increase in cell sap pH, amino acid content and ion leakage.Cycloheximide (CH), inhibitor of de novo protein synthesis, delayed significantly flower senescence when applied at a full open stage.Analysis of petal proteolytic activity during flower opening, maturation and senescence using activities gels revealed in Iris three distinct activities (25-50 kDa), detected already at the stages of closed bud, but significantly enhanced at late senescence stages.The optimal pH for these activities was 3.5, suggestive of vacuole localization.All three protease activities were eliminated by either E64 (cystein protease inhibitor), leupeptin or PMSF (serine and cysteine proteases inhibitors), and were significantly enhanced by dithiothreitol (DTT), strongly suggesting them to be cysteine proteases.
In Lisianthus petals two protease activities of 41 and 50 kDa with pH optimum at 3.5 and one activity of 82 kDa with pH optimum at 7.5 were detected.These activities, already evident during flower opening stages, peaked a initial stages of senescence but declined at more advanced stages, and were inhibited by CHI.The pH optima of the protease activities in Lisianthus are suggestive of both vacuole and cytoplasm localization.Our findings suggest that floral opening and senescence in Iris and Lisianthus are active process involving de novo protein synthesis of proteolytic enzymes.The different patterns of proteolytic activities obtained may explain the relative rates of senescence of Iris and Lisianthus cut flowers, whose vase life spans 3 or 6 days, respectively.