The Translational Apparatus of Plastids and Its Role in Plant Development

SUMMARY

Systematic reverse genetic approaches in the nuclear and chloroplast genomes have greatly increased our knowledge about the structure, function, and biogenesis of chloroplast ribosomes, and about the molecular mechanisms of plastid protein biosynthesis. They also provided new insights into the regulation of plant development by the activity of plastid gene expression. We review our current knowledge about the translational apparatus of plastids and the impact of plastid translation on plant anatomy and plant morphology.

Abstract

Chloroplasts (plastids) possess a genome and their own machinery to express it. Translation in plastids occurs on bacterial-type 70S ribosomes utilizing a set of tRNAs that is entirely encoded in the plastid genome. In recent years, the components of the chloroplast translational apparatus have been intensely studied by proteomic approaches and by reverse genetics in the model systems tobacco (plastid-encoded components) and Arabidopsis (nucleus-encoded components). This work has provided important new insights into the structure, function, and biogenesis of chloroplast ribosomes, and also has shed fresh light on the molecular mechanisms of the translation process in plastids. In addition, mutants affected in plastid translation have yielded strong genetic evidence for chloroplast genes and gene products influencing plant development at various levels, presumably via retrograde signaling pathway(s). In this review, we describe recent progress with the functional analysis of components of the chloroplast translational machinery and discuss the currently available evidence that supports a significant impact of plastid translational activity on plant anatomy and morphology.