Articles
FLOWER-SPECIFIC CAROTENOID ACCUMULATION IN CHROMOPLASTS: MOLECULAR CONTROL OF CAROTENOID-ASSOCIATED PROTEINS
Article number
420_7
Pages
32 – 34
Language
Abstract
The differentiation of chloroplasts to chromoplasts in cucumber (Cucumis sativus L.) flowers parallels flower development.
Chromoplast biogenesis involves chlorophyll degradation and carotenoid accumulation.
A chromoplast-specific 35-kD protein (chrC) was purified and characterized from Cucumis sativus corollas.
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 its expression to be 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.
The involvement of phytohormones and light in the regulation of chrC expression was studied.
When gibberellin A3 (GA3) was added to an in vitro bud culture system, accumulation of both carotenoids and chrC protein was markedly enhanced.
The specific upregulation of the latter was very rapid.
Abscisic acid and paclobutrazol, both of which counteract gibberellin, downregulated chrC accumulation when added to in vitro bud culture.
Ethylene, a growth regulator known to promote chromoplastogenesis in fruits, downregulated chrC accumulation, whereas etiolation, which has also been suggested to promote chromoplastogenesis, upregulated its accumulation.
Two additional chromoplast-specific proteins have more recently been purified by us (of 25 kD and 14 kD), the expressions of which, as shown immunologically, are also regulated in a temporal and tissue-specific manner.
Similar to chrC, the 14-kD protein is upregulated by GA3 and dark treatment, and downregulated by abscisic acid, Paclobutrazol and ethylene in vitro. Temporal, tissue-specific and GA3 upregulation of chrC is regulated at the transcriptional/post-transcriptional level as revealed by northern blot analyses, using cloned chrC as a probe.
Chromoplast biogenesis involves chlorophyll degradation and carotenoid accumulation.
A chromoplast-specific 35-kD protein (chrC) was purified and characterized from Cucumis sativus corollas.
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 its expression to be 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.
The involvement of phytohormones and light in the regulation of chrC expression was studied.
When gibberellin A3 (GA3) was added to an in vitro bud culture system, accumulation of both carotenoids and chrC protein was markedly enhanced.
The specific upregulation of the latter was very rapid.
Abscisic acid and paclobutrazol, both of which counteract gibberellin, downregulated chrC accumulation when added to in vitro bud culture.
Ethylene, a growth regulator known to promote chromoplastogenesis in fruits, downregulated chrC accumulation, whereas etiolation, which has also been suggested to promote chromoplastogenesis, upregulated its accumulation.
Two additional chromoplast-specific proteins have more recently been purified by us (of 25 kD and 14 kD), the expressions of which, as shown immunologically, are also regulated in a temporal and tissue-specific manner.
Similar to chrC, the 14-kD protein is upregulated by GA3 and dark treatment, and downregulated by abscisic acid, Paclobutrazol and ethylene in vitro. Temporal, tissue-specific and GA3 upregulation of chrC is regulated at the transcriptional/post-transcriptional level as revealed by northern blot analyses, using cloned chrC as a probe.
Authors
Y. Libal-Weksler, M. Vishnevetsky, M. Ovadis, H. Itzhaki, A. Vainstein
Keywords
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