N6-adenosine methylation of mRNA integrates multilevel auxin response and ground tissue development in Arabidopsis

N6-methyl adenosine (m6A) is a widespread internal mRNA modification impacting the expression of numerous genes. Here, we characterize auxin-related defects among the pleiotropic phenotypes of hypomorphic Arabidopsis thaliana mutants with impaired m6A status and reveal that they show strong resistance to exogenously applied auxin. By combining major published m6A datasets, we propose that among high-confidence target transcripts emerge those encoding the main components required for auxin signaling, including the TIR1/AFB auxin receptors and ARF transcriptional regulators. We also observe subtle changes in endogenous levels of indole-3-acetic acid metabolites in these hypomorphic lines, which correlate with the methylation status of indole-3-acetic acid amidohydrolase transcripts. In addition, we reveal that reduced m6A levels lead to defects in endodermal patterning in the primary root arising from impaired timing of periclinal cell divisions. These defects can be reverted by inhibition of auxin signaling. Together, our data underline that m6A likely affects auxin-dependent processes at multiple levels.