2026-05-28 ミュンヘン大学（LMU）
＜関連情報＞
- https://www.lmu.de/en/newsroom/news-overview/news/plants-exhibit-remarkable-tolerance-to-protein-translation-errors-b6b8d587.html
- https://www.pnas.org/doi/10.1073/pnas.2537357123
植物は、調節されたタンパク質恒常性によって、かなりの頻度の色素体誤翻訳に耐えることができる Plants tolerate substantial rates of plastid mistranslation via regulated proteostasis
Benjamin Brandt, Sebastian Schwartz, Serena Schwenkert, +10 , and Hans-Henning Kunz
Proceedings of the national Academy of sciences Published:May 27, 2026
DOI:https://doi.org/10.1073/pnas.2537357123
Significance
It is often assumed that the information transfer accuracy during gene expression must be high. However, translation is relatively error-prone. Under stress conditions, bacteria can benefit from mistranslation and concomitant proteome plasticity. A source for mistranslation is altered Glutaminyl-transfer RNAs (Gln-tRNAGln) synthesis that occurs through trans-amidation of Glu-tRNAGln by the aminoacyl-tRNA amido-transferase complex GatCAB. Mitochondria and plastids also employ this pathway. While the lack of GatCAB is lethal for most eukaryotes, its importance for plant cells harboring mitochondria and plastids was unknown. Using plant mutants deficient in GatCAB, we show that plastids tolerate the highest Gln-to-Glu rates reported for eukaryotes while mitochondria limit this mistranslation. Interestingly, mistranslated proteins also emerge in wild-type plants under temperature stress.
Abstract
In bacteria, protein mistranslation can improve stress tolerance. Mitochondria and plastids evolved from bacteria and use a prokaryotic-type expression machinery to synthesize proteins. Interestingly, fungi and animal mitochondria are highly sensitive to mistranslation, which for instance manifests in lethal mitochondrial cardiomyopathy disorder. The response in plant cells is unknown. Glutaminyl-transfer RNAs (Gln-tRNAGln) of bacteria and endosymbiotic organelles are synthesized indirectly. Initially, tRNAGln is aminoacylated with glutamate. Subsequently, Gln is produced through trans-amidation by the aminoacyl-tRNA amido-transferase complex GatCAB. Consequentially, compromised GatCAB activity yields misloaded Glu-tRNAGln. Arabidopsis mutants with decreased GatCAB levels provide global insights into organellar mistranslation in plants: Our proteomics analyses revealed mutant-specific high plastid and low mitochondrial Gln-to-Glu misincorporation rates in organellar-expressed protein complexes with only modest protein abundance changes in plastids and none in mitochondria. We identify efficient compensatory mechanisms that mitigate the physiological consequences of elevated mistranslation in mutants. Interestingly, wild-type plants under temperature stress also have altered Gln-to-Glu misincorporation while temperature acclimation differs in Gln-to-Glu hypermistranslating mutants. Our study indicates that the response toward organellar mistranslation varies among eukaryotes and enables future detailed investigation of mistranslation compensation mechanisms in plant cells.
