PLANT PHYSIOLOGY , Vol 106, Issue 1 217-222, Copyright © 1994 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
Regulation of Glutamate Dehydrogenase and Glutamine Synthetase in Avocado Fruit during Development and Ripening
K. A. Loulakakis, K. A. Roubelakis-Angelakis and A. K. Kanellis
Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, P.O. Box 1527, 711 10 Heraklion, Crete, Greece (K.A.K., A.K.K.)
The activity, protein, and isoenzymic profiles of glutamate de-hydrogenase
(GDH) and glutamine synthetase (GS) were studied during development and
ripening of avocado (Percea americana Mill. cv Hass) fruit. During fruit
development, the activity and protein content of both GDH and GS remained
relatively constant. In contrast, considerable changes in these enzymes
were observed during ripening of avocado fruit. The specific activity of
GDH increased about 4-fold, coincident with a similar increase in GDH
protein content and mRNA levels. On the other hand, GS specific activity
showed a decline at the end of the ripening process. On the isoenzymic
profile of GDH, changes in the prevalence of the seven isoenzymes were
found, with a predominance of the more cathodal isoenzymes in the unripe
and of the most anodal isoenzymes in the ripe fruit. Two-dimensional
electrophoresis revealed that avocado fruit GDH consists of two subunits
whose association gives rise to seven isoenzymes. The results support the
view that the predominance of the more anodal isoenzymes in the overripe
fruit was due to the accumulation of the [alpha]-polypeptide.
