Co-ordination of early and late ripening events in apples is regulated through differential sensitivities to ethylene.
In this study, it is shown that anti-sense suppression of Malus domestica 1-AMINO-CYCLOPROPANE-CARBOXYLASE OXIDASE (MdACO1) resulted in fruit with an ethylene production sufficiently low to be able to assess ripening in the absence of ethylene. Exposure of these fruit to different concentrations of exogenous ethylene showed that flesh softening, volatile biosynthesis, and starch degradation, had differing ethylene sensitivity and dependency. Early ripening events such as the conversion of starch to sugars showed a low dependency for ethylene, but a high sensitivity to low concentrations of ethylene (0.01 microl l(-1)). By contrast, later ripening events such as flesh softening and ester volatile production showed a high dependency for ethylene but were less sensitive to low concentrations (needing 0.1 microl l(-1) for a response). A sustained exposure to ethylene was required to maintain ripening, indicating that the role of ethylene may go beyond that of ripening initiation. These results suggest a conceptual model for the control of individual ripening characters in apple, based on both ethylene dependency and sensitivity.
The New Zealand Institute For Plant & Food Research Limited, Private Bag 92169, Auckland, New Zealand.
Jason W
JW
Johnston
Kularajathaven
K
Gunaseelan
Paul
P
Pidakala
Mindy
M
Wang
Robert J
RJ
Schaffer
D000594:Amino Acid Oxidoreductases / Q000235:genetics / Q000378:metabolism; D005030:Ethylenes / Q000378:metabolism*; D005638:Fruit / Q000235:genetics / Q000502:physiology; D018506:Gene Expression Regulation, Plant; D027845:Malus / Q000235:genetics / Q000502:physiology*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism
D005030:Ethylenes; D010940:Plant Proteins; C036216:ethylene; D000594:Amino Acid Oxidoreductases; C059460:1-aminocyclopropane-1-carboxylic acid oxidase