TRM61 is essential for Arabidopsis embryo and endosperm development

Post-transcriptional modifications of tRNA molecules play crucial roles in gene expression and protein biosynthesis. Across the genera, methylation of tRNAs at N 1 of adenosine 58 (A58) by AtTRM61/AtTRM6 complex plays a critical role in maintaining the stability of initiator methionyl-tRNA (tRNA i Met ). Recently, it was shown that mutation in AtTRM61 or AtTRM6 leads to seed abortion. However, a detailed study about the AtTRM61/AtTRM6 function in plants remains vague. Here, we found that AtTRM61 has a conserved functional structure and possesses conserved binding motifs for cofactor S -adenosyl-L-methionine (AdoMet). Mutations of the complex subunits AtTRM61/AtTRM6 result in embryo and endosperm developmental defects. The endosperm and embryo developmental defects were conditionally complemented by Attrm61-1/ + FIS2pro:: At TRM61 and Attrm61-1/ + ABI3pro:: At TRM61 indicating that AtTRM61 is required for early embryo and endosperm development. Besides, the rescue of the fertility defects in trm61/ + by overexpression of initiator tRNA suggests that At TRM61 mutation could diminish tRNA i Met stability. Moreover, using yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays, we showed that AtMPK4 physically interacts with AtTRM61. The data presented here suggest that AtTRM61 has a conserved structure and function in Arabidopsis. Also, AtTRM61 may be required for tRNA i Met stability, embryo and endosperm development.