Robust planar morphogenesis in leaf-like organs requires callose-dependent coordination of division and growth

Loss of a callose synthase gene in the moss Physcomitrium patens disrupts cytokinesis, producing smaller, non-planar phyllids with variable shape.

• Why it matters: Planar organ formation requires coordinating cell division and growth across mechanical layers, but bryophyte phyllids provide a minimal system to test how in-plane coordination is maintained.
• What they did: The study used quantitative live imaging plus computational modeling to link mutant phenotypes to the spatial distribution and developmental timing of local growth arrests.
• The result: Shape-defect severity is dependent on where and when growth arrests occur, showing callose-dependent coordination helps prevent mechanical conflicts and preserves planarity in monolayer organs.

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