PLANT PHYSIOLOGY , Vol 104, Issue 2 321-326, Copyright © 1994 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
Chromoplast Biogenesis in Cucumis sativus Corollas (Rapid Effect of Gibberellin A3 on the Accumulation of a Chromoplast-Specific Carotenoid-Associated Protein)
A. Vainstein, A. H. Halevy, I. Smirra and M. Vishnevetsky
The Kennedy-Leigh Center for Horticultural Research, Faculty of Agriculture, The Hebrew University of Jerusalem, Rehovot 76100, Israel
The development of cucumber (Cucumis sativus L.) corollas is accompanied by
the accumulation of chromoplasts. In mature corollas, chromoplasts, but no
chloroplasts, were detected by electron microscopy. Chlorophyll was also
undetectable in corollas at anthesis. The contents of carotenoids and a
carotenoid-associated, chromoplast-specific, 35-kD protein in corollas
increased in parallel with flower development, peaking concomitantly at
anthesis. The involvement of phytohormones and light in the regulation of
their expression was studied. When gibberellin A3 (GA3) was added to an in
vitro bud culture system, accumulation of both carotenoids and the 35-kD
protein was markedly enhanced. The specific up-regulation of the 35-kD
protein was very rapid: after only 2 h of culture, increased levels were
detected in GA3-treated versus untreated corollas. During this period,
corolla fresh weight and total protein and carotenoid contents remained
unchanged. Inclusion of abscisic acid in the culture medium counteracted
the effect of GA3. Accumulation of the 35-kD protein was also enhanced when
flower buds on plants were sprayed with GA3 or etiolated.
