PLANT PHYSIOLOGY , Vol 113, Issue 1 59-63, Copyright © 1997 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
Isolation and Regulation of Accumulation of a Minor Chromoplast-Specific Protein from Cucumber Corollas
Y. Libal-Weksler, M. Vishnevetsky, M. Ovadis and A. Vainstein
The Kennedy Leigh Center for Horticultural Research and The Otto Warburg Center for Biotechnology in Agriculture, Faculty of Agriculture, The Hebrew University of Jerusalem, Rehovot 76100, Israel
The differentiation of chloroplasts to chromoplasts in cucumber (Cucumis
sativus L.) corollas parallels flower development. Chromoplast biogenesis
involves chlorophyll degradation, carotenoid accumulation, and the
appearance of a new set of proteins. To study factors involved in
chromoplast biogenesis in floral tissues, a minor (in abundance) protein of
about 14 kD, CHRD (chromoplast protein D), was isolated from cucumber
corolla chromoplasts. Immunological characterization revealed that the
protein is chromoplast-specific and that its steady-state level in corollas
increases in parallel to flower development. The protein was not detected
in cucumber leaves or fruits. Immunological analysis of corollas and fruits
from a variety of other plants also did not reveal cross-reactivity with
the CHRD protein antisera. Using an in vitro bud culture system, we
analyzed the effect of phytohormones on CHRD expression. Gibberellic acid
rapidly enhanced, whereas paclobutrazol down-regulated, the steady-state
level of CHRD. Ethylene also down-regulated the protein's steady-state
level. It is suggested that hormonal control of chromoplastogenesis is
tightly regulated at the tissue/organ level and that mainly developmental
signals control carotenoid accumulation in nonphotosynthetic tissues.
