Abstract
BackgroundProper development of plastids in embryo and seedling tissues is critical for plant development. During germination, plastids develop to perform many critical functions that are necessary to establish the seedling for further growth. A growing body of work has demonstrated that components of the plastid transcription and translation machinery must be present and functional to establish the organelle upon germination.ResultsWe have identified Arabidopsis thaliana mutants in a gene that encodes a plastid-targeted elongation factor G (SCO1) that is essential for plastid development during embryogenesis since two T-DNA insertion mutations in the coding sequence (sco1-2 and sco1-3) result in an embryo-lethal phenotype. In addition, a point mutation allele (sco1-1) and an allele with a T-DNA insertion in the promoter (sco1-4) of SCO1 display conditional seedling-lethal phenotypes. Seedlings of these alleles exhibit cotyledon and hypocotyl albinism due to improper chloroplast development, and normally die shortly after germination. However, when germinated on media supplemented with sucrose, the mutant plants can produce photosynthetically-active green leaves from the apical meristem.ConclusionThe developmental stage-specific phenotype of the conditional-lethal sco1 alleles reveals differences in chloroplast formation during seedling germination compared to chloroplast differentiation in cells derived from the shoot apical meristem. Our identification of embryo-lethal mutant alleles in the Arabidopsis elongation factor G indicates that SCO1 is essential for plant growth, consistent with its predicted role in chloroplast protein translation.
Highlights
Proper development of plastids in embryo and seedling tissues is critical for plant development
These effects were largely negated by inhibition of photosynthesis, and their studies indicated that it is the reductant and/or ATP produced by photosynthesis in green embryos that is important for normal embryo growth and seed development
Genotypic analysis of the viable progeny showed that these plants consisted of a segregating population with a ratio of 1:2 for wild-type to heterozygote for the T-DNA insert in the SCO1 gene
Summary
Proper development of plastids in embryo and seedling tissues is critical for plant development. A growing body of work has demonstrated that components of the plastid transcription and translation machinery must be present and functional to establish the organelle upon germination In oilseed plants such as Arabidopsis (Arabidopsis thaliana) and rapeseed (Brassica napus), developing embryos are green and cells in these embryos develop functional chloroplasts [1]. A basal-state plastid must be maintained in the cells of fully mature Arabidopsis embryos since chloroplasts, amyloplasts, and the various other plastid types re-develop upon seedling germination The development of these plastids early after germination can be critical for seedling survival since, in addition to photosynthesis and the production of starch, plastids are involved in the biosynthesis of fatty acids [9], nucleic acids, and amino acids [10]
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