$\textit{N}$6-adenosinemethylationm$^{6}$AofmRNAisanessentialprocessinmosteukaryotes,butitsroleandthestatusoffactorsaccompanyingthismodificationarestillpoorlyunderstood.Usingcombinedmethodsofgenetics,proteomicsandRNAbiochemistry,weidentifiedacoresetofmRNAm$^{6}$A writer proteins in $Arabidopsis\; thaliana$. The components required for m$\mathrm{<mrow\; data-mjx-texclass="ORD">6</mrow>}$A in $Arabidopsis$ included MTA, MTB, FIP37, VIRILIZER and the E3 ubiquitin ligase HAKAI. Downregulation of these proteins led to reduced relative m$\mathrm{<mrow\; data-mjx-texclass="ORD">6</mrow>}$A levels and shared pleiotropic phenotypes, which included aberrant vascular formation in the root, indicating that correct m$\mathrm{<mrow\; data-mjx-texclass="ORD">6</mrow>}$A methylation plays a role in developmental decisions during pattern formation. The conservation of these proteins amongst eukaryotes and the demonstration of a role in writing m$\mathrm{<mrow\; data-mjx-texclass="ORD">6</mrow>}$A for the E3 ubiquitin ligase HAKAI is likely to be of considerable relevance beyond the plant sciences.