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Co-ordination of early and late ripening events in apples is regulated through differential sensitivities to ethylene.

Johnston JW, Gunaseelan K, Pidakala P, Wang M, Schaffer RJ - J. Exp. Bot. (2009)

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: The New Zealand Institute For Plant & Food Research Limited, Private Bag 92169, Auckland, New Zealand.

ABSTRACT
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.

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Conceptual model for control of individual ripening characters in apples. Ethylene sensitivity calculated from the concentration of ethylene required for a 50% ripening response. Ethylene dependency measured by the amount of ripening measured in the absence of ethylene. (This figure is available in colour at JXB online.)
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fig7: Conceptual model for control of individual ripening characters in apples. Ethylene sensitivity calculated from the concentration of ethylene required for a 50% ripening response. Ethylene dependency measured by the amount of ripening measured in the absence of ethylene. (This figure is available in colour at JXB online.)

Mentions: Ripening in apples is a complex progression of developmental steps. These steps are not completely controlled by ethylene, as there is always a degree of ethylene-independent progression. This suggests a model of ethylene action where ethylene is acting as a modulator of ripening rather than a ripening trigger. While the morphological changes that occur in apples during ripening are well documented, it is shown that these traits seem to follow an overlapping sequence of events, starting with the conversion of starch to sugars and loss of acidity, yellowing of the skin, softening of the flesh, and finally an increase in aroma volatiles. As this sequence progresses, the dependency for ethylene becomes stronger and the sensitivity to ethylene decreases (Fig. 7). For most apple cultivars, rather than having a constant level, there is an increase in ethylene during the ripening process (Johnston et al., 2001). This increase in ethylene concentration may allow the different ripening characters to be co-ordinated so that starch conversion always occurs before excessive fruit softening or the production of attractant volatiles. The low ethylene dependency for starch clearance suggests that this process is mainly driven by other developmental factors, but the high sensitivity of this process to low ethylene concentrations may provide a backup stimulus should the non-ethylene developmental cues fail to develop.


Co-ordination of early and late ripening events in apples is regulated through differential sensitivities to ethylene.

Johnston JW, Gunaseelan K, Pidakala P, Wang M, Schaffer RJ - J. Exp. Bot. (2009)

Conceptual model for control of individual ripening characters in apples. Ethylene sensitivity calculated from the concentration of ethylene required for a 50% ripening response. Ethylene dependency measured by the amount of ripening measured in the absence of ethylene. (This figure is available in colour at JXB online.)
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2692014&req=5

fig7: Conceptual model for control of individual ripening characters in apples. Ethylene sensitivity calculated from the concentration of ethylene required for a 50% ripening response. Ethylene dependency measured by the amount of ripening measured in the absence of ethylene. (This figure is available in colour at JXB online.)
Mentions: Ripening in apples is a complex progression of developmental steps. These steps are not completely controlled by ethylene, as there is always a degree of ethylene-independent progression. This suggests a model of ethylene action where ethylene is acting as a modulator of ripening rather than a ripening trigger. While the morphological changes that occur in apples during ripening are well documented, it is shown that these traits seem to follow an overlapping sequence of events, starting with the conversion of starch to sugars and loss of acidity, yellowing of the skin, softening of the flesh, and finally an increase in aroma volatiles. As this sequence progresses, the dependency for ethylene becomes stronger and the sensitivity to ethylene decreases (Fig. 7). For most apple cultivars, rather than having a constant level, there is an increase in ethylene during the ripening process (Johnston et al., 2001). This increase in ethylene concentration may allow the different ripening characters to be co-ordinated so that starch conversion always occurs before excessive fruit softening or the production of attractant volatiles. The low ethylene dependency for starch clearance suggests that this process is mainly driven by other developmental factors, but the high sensitivity of this process to low ethylene concentrations may provide a backup stimulus should the non-ethylene developmental cues fail to develop.

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: The New Zealand Institute For Plant & Food Research Limited, Private Bag 92169, Auckland, New Zealand.

ABSTRACT
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.

Show MeSH
Related in: MedlinePlus