An AINTEGUMENTA phosphoswitch controls bilateral stem cell activity during secondary growth

Plant stem cells have the remarkable ability to give rise to distinct organs and tissues throughout development. Two concentric cylinders of actively dividing stem cells are the main drivers of radial thickening during secondary growth, each producing distinct vascular cell types towards the inside and the outside. While the molecular mechanisms underlying their initiation have been well studied, it remains unclear how these stem cell layers determine which cell type is generated. Here, we demonstrate that the crosstalk between the ERECTA (ER) receptor pathway and auxin signalling controls the amount and choice of output tissue in these two stem cell regions. Mechanistically, we show that the ER pathway phosphorylates the transcription factor ANTEGUMENTA, thereby modulating bilateral stem cell activity and favouring the differentiation of only one type of cell. Our results thus show that the phosphorylation status of ANT regulates root girth and biomass accumulation by influencing bilateral stem cell production. This highlights the critical role of post-translational modifications in plant growth and development. Overall design: To investigate how auxin control bilateral stem cell activity, we performed RNA seq with pPER15::slr-GR and pPXY::shy2-2-GR roots. We transfer 12-day-old plants to either Mock or DEX plates for another 24 hours. Next, we collected only the uppermost 1.5 cm of roots (plants were grown in vitro 1/2 MS in continuous light at 22 Celsius degrees). 3 biological replicates. Each biological is from at least 100 plants