Dynamic 2'-O-Me of rRNA regulates ribosome translation in Arabidopsis nucleolin1 mutants and during seed-to-seedling transition
Across all kingdoms of life, 2'-O-ribose methylation (2'-O-Me) is the most abundant modification of ribosomal RNAs (rRNAs), which are central to ribosome assembly and function. The 2'-O-Me of specific rRNA sites is catalysed by C/D-box small nucleolar ribonucleoprotein (snoRNP) complexes. However, how and when the landscape of plant rRNA 2'-O-Me modifications is remodelled remains largely unexplored. To study the regulation of rRNA 2'-O-Me and its impact on ribosome translation, we characterised Arabidopsis NUCLEOLIN 1 (NUC1)-depleted plants, which exhibit reduced 2'-O-Me at dozens specific rRNA sites, and investigated the impact of 2'-O-Me in ribosome translation during plant development. We demonstrated that 2'-O-Me is dynamically regulated during seed-to-seedling transition. Our analysis identified differentially methylated rRNA sites, which are specifically located in structurally critical regions of the ribosome. Notably, this hypomethylation is uncoupled from the global expression, assembly, or subcellular localisation of C/D-box snoRNPs. We further observed that polysomes with low 2'-O-Me levels not only accumulate but also exhibit differential mRNA loading. These polysomes characterised by reduced 2'-O-Me at specific rRNA sites, influence multiples aspects of translation, including ribosomes stalling at the initiation, elongation and termination steps. Together, these findings advance our understanding of the dynamic regulation of rRNA 2'-O-methylation and its functional role in ribosome-mediated translation in plants.