AtTRM61/AtTRM6 complex is a bona fide tRNA N1-methyladenosine methyltransferase in Arabidopsis

tRNA molecules, which contains most abundant post-transcriptional modifications, is crucial for proper gene expression and protein biosynthesis. The methylation at N1 of adenosine 58 is critical for maintaining the stability of initiator methionyl-tRNA (tRNAiMet) in bacterial, archaeal, and eukaryotic tRNAs. How A58 of plant tRNAs is modified and involved in development remains unclear despite results obtained from yeast and mammals. Here we identified the nucleus localized complex AtTRM61/AtTRM6 as tRNA m1A58 methyltransferase in Arabidopsis. Deficiency or lacking of either AtTRM61 or AtTRM6 leads to embryo arrest and seed abortion. The tRNA m1A level decreased in conditionally complemented attrm61/LEC1pro::AtTRM61 plant, accompanied with reduced tRNAiMet level, indicating the importance of tRNA m1A modification for tRNAiMet stability. Together, we demonstrated that tRNA m1A58 modification is necessary to tRNAiMet stability and required for embryo development in plant.