LAUSR

meristem, auxin feeds back on the direction of its transport via the auxin response transcription factor MONOPTREOS (MP). By perturbing MP activity both globally and locally we show that localized MP activity is necessary for the generation of PIN1 convergence patterns and that localized MP expression is sufficient to orient PIN1 polarity towards MP expressing cells non-cell autonomously. By restricting MP to the epidermis of mp mutants we also show that although MP activity in a single cell layer is sufficient to generate periodic polarity patterns, MP is required in sub-epidermal tissues to stabilize these patterns with respect to the underlying cells. Overall our findings reveal a patterning mechanism in plants that involves feedback between the intercellular transport of a morphogen and its downstream transcriptional targets.