Abstract
In animals and plants, organ shape is primarily determined during primordium development by carefully coordinated growth and cell division1-3. Rare examples of post-primordial change in morphology (reshaping) exist that offer tractable systems to study mechanisms required for organ-shape determination and diversification. One such example is the heart-shape formation ofCapsellafruits that occurs by reshaping the ovate spheroid gynoecium upon fertilization4. Here we use whole-organ live-imaging to show that dynamic changes in growth and cell division coupled with local maintenance of meristematic identity drivesCapsellafruit-shape formation. At the molecular level, we reveal an auxin-induced mechanism ultimately descending on a singlecisregulatory element to mediate morphological alteration. This element resides in the promoter of theCapsella rubella SHOOTMERISTEMLESS5(CrSTM) gene. The CrSTM meristem identity factor positively regulates its own expression through binding to this element thereby providing a feed-forward loop at the position and time when protrusions emerge to form the heart. Independent evolution of the STM-binding element inSTMpromoters across Brassicaceae species correlates with those undergoing a gynoecium-to-fruit metamorphosis. Accordingly, genetic and phenotypic studies showed that the STM-binding element is required to facilitate the shape transition and reveals a conserved molecular mechanism for organ morphogenesis.
Publisher
Cold Spring Harbor Laboratory