Recurrent requirement for the mA-ECT2/ECT3/ECT4 axis in the control of cell proliferation during plant organogenesis.

mRNA methylation at the position of adenosine (mA) enables multiple layers of post-transcriptional gene control, often via RNA-binding proteins that use a YT521-B homology (YTH) domain for specific mA recognition. In , normal leaf morphogenesis and rate of leaf formation require mA and the YTH-domain proteins ECT2, ECT3 and ECT4. In this study, we show that and mutants also exhibit slow root and stem growth, slow flower formation, defective directionality of root growth, and aberrant flower and fruit morphology. In all cases, the mA-binding site of ECT proteins is required for function. We also demonstrate that both mA methyltransferase mutants and exhibit aberrant floral phyllotaxis. Consistent with the delayed organogenesis phenotypes, we observe particularly high expression of , and in rapidly dividing cells of organ primordia. Accordingly, mutants exhibit decreased rates of cell division in leaf and vascular primordia. Thus, the mA-ECT2/ECT3/ECT4 axis is employed as a recurrent module to stimulate plant organogenesis, at least in part by enabling rapid cellular proliferation.