Translational regulation in chloroplasts for development and homeostasis

Abstract

Chloroplast genomes encode 100-200 proteins which function in photosynthesis, the organellar genetic system, and other pathways and processes. These proteins are synthesized by a complete translation system within the chloroplast, with bacterial-type ribosomes and translation factors. Here, we review translational regulation in chloroplasts, focusing on changes in translation rates which occur in response to requirements for proteins encoded by the chloroplast genome for development and homeostasis. In addition, we delineate the developmental and physiological contexts and model organisms in which translational regulation in chloroplasts has been studied. This article is part of a Special Issue entitled: Chloroplast biogenesis.

Organellar Gene Expression and Acclimation of Plants to Environmental Stress

“…Since sessile plant species cannot escape from unfavorable environmental conditions, it is conceivable that they have had to develop more flexible response mechanisms. Indeed, it is generally accepted that the control of PGE has shifted to post-transcriptional events over the course of evolution (Barkan and Goldschmidt-Clermont, 2000; Stern et al, 2010), especially in mature chloroplasts (Sun and Zerges, 2015). Thus, unlike redox regulation of transcription in mustard (Pfannschmidt et al, 1999) and ABA-mediated repression of transcriptional activity of chloroplast genes in barley (Yamburenko et al, 2013), levels of individual plastid mRNAs in spinach (Klaff and Gruissem, 1991) and barley (Kim et al, 1993) during plant development are mainly determined by alterations in stability, with half-lifes of many hours or even days – much more stable than bacterial mRNAs with typical lifetimes of seconds to hours (Radhakrishnan and Green, 2016).…”

“…Plastid proteins are synthesized by bacterial-type 70S ribosomes using a set of tRNAs that is entirely encoded in the plastid genome (Tiller and Bock, 2014; Sun and Zerges, 2015). The plastid ribosome itself consists of the large (50S) and small (30S) multi-component ribosomal subunits, each comprising one or more plastid-encoded ribosomal RNA species (rRNAs), and furthermore, plastid- and nuclear-encoded proteins (Yamaguchi and Subramanian, 2000; Yamaguchi et al, 2000).…”

Cryo-EM structure of the spinach chloroplast ribosome reveals the location of plastid-specific ribosomal proteins and extensions

“…The origin of chloroplasts is thought to result from an endosymbiotic event where an early eukaryotic cell engulfed a photosynthetic cyanobacterium (1). As such chloroplasts possess their own genome, as well as the transcription and translation machinery to convert the genetic information into polypeptides or proteins (2,3). Chloroplast ribosomes, or chlororibosomes, are very specialized since they are only involved in synthesizing the limited number of proteins encoded in the chloroplast genome (2,3).…”

Three-Dimensional Visualization of the Tubular-Lamellar Transformation of the Internal Plastid Membrane Network during Runner Bean Chloroplast Biogenesis

“…It involves changes in gene expression together with the transcriptional and translational control of both nuclear and plastid genes. These genes can be regulated by anterograde and retrograde signals, the synthesis of necessary lipids and pigments, the import and routing of the nucleusencoded proteins into plastids, protein-lipid interactions, the insertion of proteins into the plastid membranes, and the assembly into functional complexes (Vothknecht and Westhoff, 2001;Baena-González and Aro, 2002;Kota et al, 2002;Stern et al, 2004;López-Juez, 2007;Waters and Langdale, 2009;Solymosi and Schoefs, 2010;Adam et al, 2011;Pogson and Albrecht, 2011;Ling et al, 2012;Jarvis and López-Juez, 2013;Lyska et al, 2013;Belcher et al, 2015;Börner et al, 2015;Dall'Osto et al, 2015;Ling and Jarvis, 2015;Rast et al, 2015;Sun and Zerges, 2015;Yang et al, 2015). Chloroplast biogenesis is highly integrated with cell and plant development, especially with photomorphogenesis (Pogson et al, 2015), and is controlled by cellular and organismal regulatory mechanisms such as the ubiquitin-proteasome system (Jarvis and López-Juez, 2013).…”