Fig. 2

TRDMT1 and TRM4B methylate Arabidopsis nuclear encoded transfer RNAs. a Genomic origins of methylated and non-methylated tRNAs. Methylated tRNAs were only detected from the nuclear genome (3 biological replicates). b Above: clover-leaf representative secondary structure of tRNA indicating in red, the five cytosine positions methylated in wild type. Below: Heatmap showing percentage methylation of all cytosines detected in nuclear tRNAs of wild type, and mutants trdmt1, trm4a, trm4b-1 and trdmt1 trm4b using RBS-seq. Cytosine positions are indicated next to tRNA isodecoders. White boxes represent cytosine positions with coverage less than five reads. (wild type 3 biological replicates, mutants n = 1). c Genomic structure of trm4a and trm4b mutants showing T-DNA insertions (triangles) in exons (filled boxes). d Analysis of RNA methylation by TRDMT1 at position C38 on BS treated tRNA^Asp(GTC) template. Above: Restriction maps of PCR amplified products showing the expected digest patterns of methylated and non-methylated template. Below: Cleavage of PCR amplified product by HpyCH4IV confirms C38 methylation in wild type as opposed to non-methylated C38 in trdmt1 results in loss of HpyCH4IV restriction site. Loading control is undigested PCR product. e Hygromycin B stress assay. Trdmt1 trm4b double mutants and to a lesser extent, trm4b-1 mutants display increased sensitivity to hygromycin B (Hyg) at 10 and 20 days after germination (DAG) compared to controls