Dev. Cell 38, 186–200 (2016)

Credit: ELSEVIER

N6-Methyladenosine (m6A) is a post- transcriptional mRNA modification installed by a methyltransferase complex composed of METTL3, METTL14 and WTAP. Although m6A modifications have been observed in a variety of organisms, probing their biological function is challenging because loss-of-function mutations affecting the methyltransferase complexes, for instance in the Arabidopsis WTAP homolog FIP37, often result in embryonic lethality. Shen et al. provided transgenic rescue of FIP37 function to fip37 mutants during embryonic development and observed that the rescued mutants exhibited an expansion of the shoot apical meristem (SAM), a tissue containing stem cells that generates all aerial organs, with a corresponding loss of leaves and flowers. In situ hybridization analysis revealed that FIP37 was expressed in the SAM and that two SAM regulators, WUSCHEL (WUS) and SHOOTMERISTEMLESS (STM), showed expanded spatial mRNA expression in fip37 mutants. m6 A sites were found near the stop codon and 3′ UTR in WUS and STM RNA transcripts and were lost in fip37 mutants. The increased STM and WUS RNA expression detected in fip37 mutants was attributed to increased RNA stability, suggesting that m6A methylation promotes RNA decay and confines WUS and STM mRNA expression to the SAM. Overall, these findings reveal a developmental role of m6A modification in balancing the maintenance and differentiation of a plant stem cell population.