The Arabidopsis Cytosolic Ribosomal Proteome: From form to Function

Abstract

The cytosolic ribosomal proteome of Arabidopsis thaliana has been studied intensively by a range of proteomics approaches and is now one of the most well characterized eukaryotic ribosomal proteomes. Plant cytosolic ribosomes are distinguished from other eukaryotic ribosomes by unique proteins, unique post-translational modifications and an abundance of ribosomal proteins for which multiple divergent paralogs are expressed and incorporated. Study of the A. thaliana ribosome has now progressed well beyond a simple cataloging of protein parts and is focused strongly on elucidating the functions of specific ribosomal proteins, their paralogous isoforms and covalent modifications. This review summarises current knowledge concerning the Arabidopsis cytosolic ribosomal proteome and highlights potentially fruitful areas of future research in this fast moving and important area.

Mechanism of Cytoplasmic mRNA Translation

“…RACK1 is stably associated with the 40S ribosomal subunit of Arabidopsis Giavalisco et al, 2005;Carroll et al, 2008;Piques et al, 2009;Turkina et al, 2011;Hummel et al, 2012;Carroll, 2013), as in other eukaryotes. This protein has a seven bladed β-propeller domain that allows it to act as a scaffold, in a manner homologous to the heterotrimeric G protein Gβ subunit.…”

“…RP transcript levels are also differentially regulated between cell types (e.g., (Mustroph et al, 2009). Other sources of ribosome heterogeneity include N-terminal methionine removal, N-terminal acetylation, methylation of lysine and proline residues and phosphorylation of serine and threonine residues of RPs (Bailey-Serres and Freeling, 1990;Bailey-Serres et al, 1997;Szick-Miranda and Bailey-Serres, 2001;Williams et al, 2003;Chang et al, 2005;Carroll et al, 2008;Turkina et al, 2011;Hummel et al, 2012;Boex-Fontvieille et al, 2013;Carroll, 2013). The functional consequence of ribosome heterogeneity is largely unknown, but may provide for a complex regulatory network that impacts translation at the global or mRNA specific level.…”

“…Proteomic studies using 1D and 2D mass spectrometry have obtained evidence for the product of a least one paralog of each RP family in purified ribosomes, with the exception of the small (~3.5 kDa) and highly basic RPL41 (reviewed by Carroll, 2013). b Two RPS15a paralogs encode RPs that assemble into mitochondrial and not cytosolic ribosomes (Carroll et al, 2008).…”

“…Ribosomes purified by differential centrifugation yielded 31-33 of the putative 40S RPs and 48 of the putative 60S RPs, respectively Giavalisco et al, 2005;Carroll et al, 2008;Piques et al, 2009;Turkina et al, 2011;Carroll, 2013). An analysis performed on ribosomes captured by immunopurification, thereby limiting contamination by organellar ribosomes and other co-sedimenting complexes, confirmed products from 204 of the estimated 232 functional RP genes of A. thaliana based on two or more prototypic peptides (Hummel et al, 2012).…”

New Evidence for Differential Roles of L10 Ribosomal Proteins from Arabidopsis

“…In Arabidopsis (Arabidopsis thaliana), ribosomal protein genes exist as families composed of two to seven members that could be differentially incorporated into the cytosolic ribosome under specific situations (Schmid et al, 2005;Byrne, 2009). In this way, ribosomal heterogeneity would allow selective translation of specific mRNAs under particular cell conditions (Barakat et al, 2001;Szick-Miranda and BaileySerres, 2001;Giavalisco et al, 2005;Carroll et al, 2008;Carroll, 2013). Arabidopsis mutants in ribosomal proteins exhibit a large range of developmental phenotypes with extreme abnormalities, including embryonic lethality, suggesting that ribosomes also have specific functions regulating the expression of developmental genes (Van Lijsebettens et al, 1994;Degenhardt and Bonham-Smith, 2008;Byrne, 2009;Horiguchi et al, 2011Horiguchi et al, , 2012Szakonyi and Byrne, 2011).…”