The Arabidopsis TRM61/TRM6 complex is a bona fide tRNA N1-methyladenosine methyltransferase

tRNA molecules, which contain the most abundant post-transcriptional modifications, are crucial for proper gene expression and protein biosynthesis. Methylation at N-1 of adenosine 58 (A58) is critical for maintaining the stability of initiator methionyl-tRNA (tRNAi(Met)) in bacterial, archaeal, and eukaryotic tRNAs. However, although research has been conducted in yeast and mammals, it remains unclear how A58 in plant tRNAs is modified and involved in development. In this study, we identify the nucleus-localized complex AtTRM61/AtTRM6 in Arabidopsis as tRNA m(1)A58 methyltransferase. Deficiency or a lack of either AtTRM61 or AtTRM6 leads to embryo arrest and seed abortion. The tRNA m(1)A level decreases in conditionally complemented Attrm61/LEC1pro::AtTRM61 plants and this is accompanied by reduced levels of tRNAi(Met), indicating the importance of the tRNA m(1)A modification for tRNAi(Met) stability. Taken together, our results demonstrate that tRNA m(1)A58 modification is necessary for tRNAi(Met) stability and is required for embryo development in Arabidopsis.