Final Report Summary - MHDVPATTERNING (The establishment and function of dorsiventral boundaries in plant organs)
The dorsal (top) and ventral (bottom) sides of plant leaves have distinct functions in photosynthesis and gas exchange respectively. Here we analysed the developmental origins of that distinction in Arabidopsis and investigated how boundaries between dorsal and ventral cell types regulate plant architecture. Our results reveal that boundaries between dorsal Class III homeodomain-leucine zipper (HD-ZIP) and ventral KANADI gene expression act within the shoot and developing leaves to control leaf shape and position. Using mosaic analysis we also show that juxtaposition of dorsal and ventral gene expression is sufficient to induce ectopic leaf tissue, confirming that dorsoventral boundaries in plants act analogously to boundary-localized organizers in animals. Our analysis also uncovers many regulatory relationships between genes involved in dorsoventral patterning and in particular, we have elucidated a molecular pathway involving the plant hormone auxin, by which dorsoventral boundaries influence plant growth. Together these results clarify the role of dorsoventral boundaries in plant development and highlight contrasting molecular mechanisms behind organiser activity in plants and animals.