Donghwi Ko, Raili Ruonala, Alexandre Faille, Eva Hellmann, Hanna Help, Huili Liu, Ronni Nielsen, Anders Haakonsson, Nuria De Diego, Anja Paatero, Mariia Shcherbii, Karolina Stefanowicz, Sanja Ćavar Zeljkovıć, Tine Drud Lundager Rasmussen, Ondrej Novak, Zsuzsanna Bódi, Gugan Eswaran, Brecht Wybouw, Matthieu Bourdon, Cristina Úrbez, Xiaonan Liu, Kari Salokas, Tiina Öhman, Tanya Waldie, Petri Törönen, Sedeer El‐Showk, Martin Balcerowicz, Fabrice Besnard, Xiaomin Liu, Patrick Perkins, Serina Mazzoni-Putman, Julia P. Vainonen, Maija Sierla, Mikko J. Frilander, Susanne Mandrup, Teva Vernoux, Karin Ljung, A. Tormos Ferrando, Miguel A. Blazquez, Liisa Holm, Rupert G. Fray, Markku Varjosalo, Ottoline Leyser, Ville O. Paavilainen, Ari Pekka Mähönen, Anna N. Stepanova, Jose Alonso, Steffen Heber, Robert Malinowski, Finn Kirpekar, Alan J. Warren, Ykä Helariutta
Polyamines are often associated with ribosomes and are thought to stabilize their integrity. In Arabidopsis , the polyamine thermospermine (tSpm) affects xylem cell fate. tSpm induces translation of SUPPRESSOR-OF-ACAULIS51 (SAC51) and SAC51-LIKEs (SACLs), which inhibit heterodimerization of the xylem development proteins LONESOME-HIGHWAY (LHW) and TARGET-OF-MONOPTEROS5. Here, we report a methyltransferase, OVERACHIEVER, that methylates the peptidyl transferase center of the 25 S ribosomal RNA (rRNA). Residue m 3 U2952 promotes functional tSpm binding to a specific site connecting the P-site transfer RNA (tRNA) with rRNA residues in the peptidyl transferase center. This interaction enhances the translation of SACLs but inhibits that of LHW. Our study uncovers the dependency between a conserved rRNA base methylation and a polyamine in orchestrating cell fate decisions, highlighting a role for the ribosome chemical landscape in translational regulation.