Mutual inhibition between EPFL2 and auxin extends the intervals of periodic leaf morphogenesis.

Rules behind the spatial arrangement of repetitive modules are key principles of multicellular morphogenesis. In plant shoots, PIN-FORMED 1 (PIN1)-mediated polar auxin transport instructs periodic formation of auxin maxima, which develop into lateral organs or leaf serrations. However, it remains unknown how the intervals of regularly arising auxin maxima are controlled. Here we show that a cysteine rich peptide EPIDERMAL PATTERNING FACTOR-LIKE 2 (EPFL2) dose-dependently determines the intervals of auxin maxima during serration formation in leaf primordia. EPFL2 constitutes a mutually repressive relationship with cellular auxin response, thereby produces bistable states. Based on our computational simulations, we propose that the bistability modulates the periodicity of PIN1-mediated auxin maxima formation. Moreover, EPFL2 ensures precise phyllotactic angles, underscoring the general role of EPFL2 in auxin-mediated shoot patterning. This study illustrates that the intercoupling between EPFL2-auxin bistable module and PIN1-mediated polar auxin transport underpins versatile periodicity in auxin maxima formation during shoot development.