Articles
THE ROLE OF ETHYLENE IN REGULATING CELL WALL-DEGRADING ENZYME ACTIVITY USING ANTISENSE ACC-OXIDASE IN CANTALOUPE MELONS
Article number
510_74
Pages
471 – 478
Language
Abstract
Transgenic Charentais-type melons (Cucumis melo var. cantalupensis cv.
Védrantais) exhibiting strong inhibition of ethylene production were used as a model in comparison with the corresponding wild-type fruit in order to better understand the role of ethylene in the regulation of the activity of cell wall-degrading enzymes.
Transgenic fruits were treated with 1.0 ppm, 2.5 ppm, and 5.0 ppm ethylene for five days, and endo-PG, exo-PG, pectin methyl esterase, glycosidase (
-galactosidase and 
-arabinosidase), and galactanase activities were assayed.
The 1.0 ppm ethylene treatment had no significant effect on all activities except that of-galactosidase.
The threshold level of ethylene capable of stimulating activities was 2.5 ppm whilst 5.0 ppm was saturating.
These levels are in agreement with the levels of ethylene needed for stimulating softening.
A fraction of the activities was present in the ethylene-inhibited transgenic fruits.
This fraction can be considered as ethylene-independent.
The portion of the activity that increases during ripening of wild-type fruit and stimulated by ethylene in transgenic fruit may correspond to additional ethylene-sensitive isoforms of the enzymes.
Cell-wall degradation in melon is therefore regulated by ethylene-dependent and ethylene-independent events.
Védrantais) exhibiting strong inhibition of ethylene production were used as a model in comparison with the corresponding wild-type fruit in order to better understand the role of ethylene in the regulation of the activity of cell wall-degrading enzymes.
Transgenic fruits were treated with 1.0 ppm, 2.5 ppm, and 5.0 ppm ethylene for five days, and endo-PG, exo-PG, pectin methyl esterase, glycosidase (
-galactosidase and -arabinosidase), and galactanase activities were assayed.The 1.0 ppm ethylene treatment had no significant effect on all activities except that of
-galactosidase.The threshold level of ethylene capable of stimulating activities was 2.5 ppm whilst 5.0 ppm was saturating.
These levels are in agreement with the levels of ethylene needed for stimulating softening.
A fraction of the activities was present in the ethylene-inhibited transgenic fruits.
This fraction can be considered as ethylene-independent.
The portion of the activity that increases during ripening of wild-type fruit and stimulated by ethylene in transgenic fruit may correspond to additional ethylene-sensitive isoforms of the enzymes.
Cell-wall degradation in melon is therefore regulated by ethylene-dependent and ethylene-independent events.
Authors
R. Botondi, M. Cardarelli, F. Mencarelli
Keywords
cell wall-degrading enzymes, Cucumis melo, transgenic
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