Highlight OsTRM13 is a 2′-O-methyladenosine tRNA nucleoside modification gene that positively regulates salt stress tolerance in rice.

Modified nucleosides on tRNA are critical for decoding processes and protein translation. tRNAs can be modified through 1-methylguanosine (m1G) on position 37; a function mediated by Trm5 homologs. We show that AtTRM5a (At3g56120) is a Trm5 ortholog in Arabidopsis thaliana. AtTrm5a is localized to the nucleus and its function for m1G and m1I methylation was confirmed by mutant analysis, yeast complementation, m1G nucleoside level on single tRNA, and tRNA in vitro methylation. Arabidopsis attrm5a mutants were dwarfed and had short filaments, which led to reduced seed setting. Proteomics data indicated differences in the abundance of proteins involved in photosynthesis, ribosome biogenesis, oxidative phosphorylation and calcium signalling. Levels of phytohormone auxin and jasmonate were reduced in attrm5a mutant, as well as expression levels of genes involved in flowering, shoot apex cell fate determination, and hormone synthesis and signalling. Taken together, loss-of-function of AtTrm5a impaired m1G and m1I methylation and led to aberrant protein translation, disturbed hormone homeostasis and developmental defects in Arabidopsis plants.

Our understanding of how aging affects the cellular and molecular components of the human ovary and contributes to age-related fertility decline is still limited. Here, we link single-cell RNA sequencing and spatial transcriptomics to characterize human ovarian aging. Changes of the molecular signatures of eight types of ovarian cells during aging were defined. We combined single cell types with their spatial location information to divide ovarian granulosa cells into three subtypes and theca & stroma cells into five subtypes. Further analysis revealed increased cellular senescence with age and characterized the transcription factor FOXP1 as a master regulatory gene during ovarian aging. Inhibition of FOXP1 in ovarian cells increased cellular senescence which was alleviated by pharmacological treatment with quercetin or fisetin. These findings provide a comprehensive understanding of the spatiotemporal variability of human ovarian aging, providing resources for developing new diagnostic biomarkers and therapeutic strategies against ovarian aging.