PLANT PHYSIOLOGY , Vol 102, Issue 2 491-496, Copyright © 1993 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
Isolation and Characterization of a Chromoplast-Specific Carotenoid-Associated Protein from Cucumis sativus Corollas
I. Smirra, A. H. Halevy and A. Vainstein
Department of Horticulture, Faculty of Agriculture, The Hebrew University of Jerusalem, Rehovot 76100, Israel
The differentiation of chloroplasts to chromoplasts in corollas of cucumber
(Cucumis sativus) is subject to developmental control. To study factors
involved in the chloroplast-chromoplast conversion, a chromoplast-specific
protein of 35 kD was isolated, and polyclonal antibodies were prepared
against it. This protein was found to be a principal component of the
carotenoid-protein complex resolved from chromoplast membranes by
nondenaturing gel electrophoresis. Immunological studies revealed that
expression of this protein is regulated in a temporal and tissue-specific
manner. Its steady-state level increased in parallel with flower
development and carotenoid accumulation, peaking in mature flowers and then
rapidly decreasing to very low levels. The protein was not detectable in
cucumber leaves or fruits. To ascertain whether an organ-specific system
regulates the chloroplast-chromoplast conversion and to enable future
molecular studies of factors involved in this regulation, an in vitro bud
culture system was established. Patterns of expression of the 35-kD protein
and carotenoids in corollas of detached buds were similar to those in
intact buds.
