Cell wall patterning regulates plant stem cell dynamics.

Abstract

The plant cell wall regulates development through spatiotemporal modulation of its chemical and mechanical properties. Pectin methylesterification is recognized as a rheological switch controlling wall stiffness. Here, we reveal a bimodal methylesterification pattern in the shoot meristem: Mature walls exhibit high methylesterification, whereas demethylesterified pectins are deposited at new cross walls. This spatial heterogeneity is established through nuclear sequestration of <i>PECTIN METHYLESTERASE5</i> (<i>PME5</i>) mRNA. MYB3R4-driven transcription, combined with RZ-1B/1C-mediated retention, creates a mitotically associated <i>PME5</i> mRNA reservoir in the nucleus. Nuclear envelope disassembly synchronizes <i>PME5</i> messenger RNA (mRNA) release with cell plate formation, enabling precise demethylesterification at division planes. Perturbation of this spatial control compromises stem cell maintenance or breaks division patterning. Our study uncovers an mRNA compartmentalization mechanism that couples stem cell dynamics with pectin modification.