Characterization of the Snowy Cotyledon 1 Mutant of Arabidopsis Thaliana: The Impact of Chloroplast Elongation Factor G on Chloroplast Development and Plant Vitality |
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Authors: | Verónica Albrecht Anke Ingenfeld Klaus Apel |
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Institution: | (1) Institute of Plant Sciences, Swiss Federal Institute of Technology (ETH), Zurich, Switzerland |
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Abstract: | During seedling development chloroplast formation marks the transition from heterotrophic to autotrophic growth. The development
and activity of chloroplasts may differ in cotyledons that initially serve as a storage organ and true leaves whose primary
function is photosynthesis. A genetic screen was used for the identification of genes that affect selectively chloroplast
function in cotyledons of Arabidopsis thaliana. Several mutants exhibiting pale cotyledons and green true leaves were isolated and dubbed snowy cotyledon (sco).One of the mutants, sco1, was characterized in more detail. The mutated gene was identified using map-based cloning. The mutant contains a point mutation
in a gene encoding the chloroplast elongation factor G, leading to an amino acid exchange within the predicted 70S ribosome-binding
domain. The mutation results in a delay in the onset of germination. At this early developmental stage embryos still contain
undifferentiated proplastids, whose proper function seems necessary for seed germination. In light-grown sco1 seedlings the greening of cotyledons is severely impaired, whereas the following true leaves develop normally as in wild-type
plants. Despite this apparent similarity of chloroplast development in true leaves of mutant and wild-type plants various
aspects of mature plant development are also affected by the sco1 mutation such as the onset of flowering, the growth rate, and seed production. The onset of senescence in the mutant and
the wild-type plants occurs, however, at the same time, suggesting that in the mutant this particular developmental step does
not seem to suffer from reduced protein translation efficiency in chloroplasts. |
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Keywords: | chloroplast development chloroplast protein biosynthesis snowy cotyledon 1 plant vitality |
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