A premitotic polarity program patterns the grass leaf epidermis.

Premitotic polarization of BdPL1 is essential for transverse asymmetric cell divisions that pattern the grass leaf epidermis in Brachypodium distachyon.

• Why it matters: Understanding how epidermal cell patterning occurs in grasses can reveal fundamental mechanisms of plant development and may inform crop improvement strategies.
• What they did: The study used loss-of-function and ectopic expression analyses of BdPL1, along with investigations of developmental regulators BdBREVIS RADIX-solo and BdYODA1, to examine their roles in cell division and fate determination.
• The result: Disruption of BdPL1 caused defects in division-plane orientation and cell-size asymmetry, impairing epidermal patterning, while the combined action of premitotic and postmitotic modules ensures robust leaf epidermis patterning.