Abstract
BackgroundModification of nucleosides on transfer RNA (tRNA) is important either for correct mRNA decoding process or for tRNA structural stabilization. Nucleoside methylations catalyzed by MTase (methyltransferase) are the most common type among all tRNA nucleoside modifications. Although tRNA modified nucleosides and modification enzymes have been extensively studied in prokaryotic systems, similar research remains preliminary in higher plants, especially in crop species, such as rice (Oryza sativa). Rice is a monocot model plant as well as an important cereal crop, and stress tolerance and yield are of great importance for rice breeding.ResultsIn this study, we investigated how the composition and abundance of tRNA modified nucleosides could change in response to drought, salt and cold stress, as well as in different tissues during the whole growth season in two model plants–O. sativa and Arabidopsis thaliana. Twenty two and 20 MTase candidate genes were identified in rice and Arabidopsis, respectively, by protein sequence homology and conserved domain analysis. Four methylated nucleosides, Am, Cm, m1A and m7G, were found to be very important in stress response both in rice and Arabidopsis. Additionally, three nucleosides,Gm, m5U and m5C, were involved in plant development. Hierarchical clustering analysis revealed consistency on Am, Cm, m1A and m7G MTase candidate genes, and the abundance of the corresponding nucleoside under stress conditions. The same is true for Gm, m5U and m5C modifications and corresponding methylation genes in different tissues during different developmental stages.ConclusionsWe identified candidate genes for various tRNA modified nucleosides in rice and Arabidopsis, especially on MTases for methylated nucleosides. Based on bioinformatics analysis, nucleoside abundance assessments and gene expression profiling, we propose four methylated nucleosides (Am, Cm, m1A and m7G) that are critical for stress response in rice and Arabidopsis, and three methylated nucleosides (Gm, m5U and m5C) that might be important during development.
Highlights
Modification of nucleosides on transfer RNA is important either for correct mRNA decoding process or for tRNA structural stabilization
Identification of tRNA MTase candidate genes in rice and Arabidopsis O. sativa and A. thaliana were selected for the monocot or the dicot model organism. tRNA MTase candidate genes were identified based on protein sequence homology with yeast tRNA MTases
We have shown that abscisic acid (ABA) treatment induced a significant increase of Am nucleosides in rice seedlings [28]
Summary
Modification of nucleosides on transfer RNA (tRNA) is important either for correct mRNA decoding process or for tRNA structural stabilization. In Arabidopsis, a few components of the Elongator complex (ELP1–6, KTI11–14) were shown to regulate cell proliferation, anthocyanin biosynthesis, drought stress tolerance and immune response [14,15,16,17,18] These genes participated in ncm5U (5-carbamoylmethyluridine) modification at position 34 on certain tRNA species [19,20,21]. It has been long postulated that modified nucleosides on tRNA molecules may function as “biosensor” for environmental and physiological changes [24, 25], as a fast module to regulate gene expression at translational level In agreement with this hypothesis, the abundance of tRNA modified nucleosides do change in response to various stresses [26]. Overexpression of OsTRM13, the corresponding gene for Am and Cm modification at position 4, improved salt stress tolerance in rice [28]
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