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Figure 1. 

Working model for RZ-1B/1C–PME5-mediated precise pectin modification in stem cell dynamics and meristem homeostasis. During formation and maintenance of the shoot apical meristem, PME5 transcripts (encoding a cell-wall pectin methylesterase) are not immediately exported to the cytoplasm after transcription but are bound by the nuclear RNA-binding proteins RZ-1B and RZ-1C, and retained within the nucleus, thereby limiting PME5 protein production, and maintaining a highly methyl-esterified pectin state in pre-existing cell walls. Upon entry into mitosis and nuclear-envelope breakdown, the previously sequestered PME5 mRNAs are rapidly released into the cytoplasm and are efficiently translated into PME5 protein. Zhu et al.^[17] propose that newly synthesized PME5 is transported through the secretory pathway to specific domains of the nascent cell wall, where it catalyzes local pectin demethylesterification. This spatially and temporally restricted remodeling of pectin architecture is proposed to fine-tune cell-wall mechanical properties and the local extracellular microenvironment, thereby contributing to the coordination of stem-cell behaviour with shoot apical meristem homeostasis. Created in BioRender: https://BioRender.com/6edfu6t.