Abstract

Plant stem cells have the remarkable ability to give rise to distinct tissues and organs 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 cross-talk 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 AINTEGUMENTA, 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. SignificanceThis study uncovers a critical regulatory mechanism governing bilateral stem cell activity during plant radial growth. Stem cells in the cambia proliferate and differentiate into specialized tissues like wood and cork, key sites of biomass accumulation. By exploring the interplay between the ERECTA (ER) receptor and auxin signalling, we reveal how these pathways modulate stem cell differentiation and radial thickening through the phosphorylation of the transcription factor AINTEGUMENTA (ANT). Phosphorylation status of ANT modulates stem cell activity, dictating the production of specific vascular cell types like wood thus controlling root girth. This research underscores the importance of post-translational modifications in plant development and provides a novel regulation underpinning stem cell differentiation, with significant implications for enhancing biomass accumulation as wood.