ISHS Acta Horticulturae 179: V International Symposium on Growth Regulators in Fruit Production
REGULATION OF ETHYLENE BIOSYNTHESIS IN RIPENING APPLE FRUITS |
| Authors: | S.F. Yang, Y. Liu, O.L. Lau |
| Abstract:
Ethylene is an important plant hormone regulating many aspects of plant growth and development including fruit ripening. Ethylene was shown first in apple tissue to be biosynthesized by the following pathway: methionine —> S-adenosylmethionine (SAM) —> l-amino- cyclopropane-1-carboxylic acid (ACC) —> ethylene. This pathway has since been shown to operate in all plant tissues. Climacteric fruits are characterized by a surge of ethylene production at the onset of ripening. Since preclimacteric fruits lack not only the ability to convert SAM to ACC (ACC synthase) but also the ability to convert ACC to ethylene (EFE, ethylene-forming enzyme), the ripening process involves the development of both ACC synthase and EFE. The time courses of the onset of the increases in ethylene production, in the development of EFE and in ACC level were examined throughout the ripening process in apple fruits (cv. Golden Delicious) detached from the tree at the preclimacteric stage or attached to the tree. Comparing the changes in ACC and the development of EFE in attached and detached fruits reveals that attachment ("tree factor") suppresses the development of both ACC synthase and EFE. During the commencement of ripening of detached or attached fruits, the increase in ethylene production coincides with the development of EFE, which is followed by the increase in ACC level. The possible role of ethylene in inducing autocatalytic production of ethylene and the associated ripening process is discussed. | |
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