Round Table Seminar - Nathanaël Prunet, (TP Jack Lab, Dartmouth College) SUPERMAN and the definition of the boundary between male and female organs in the Arabidopsis flower

Event Dates: May 14, 2014 - 4:00am - 5:00am

While the mechanisms that control floral organ identity are well known, how the boundary between the different floral whorls is defined remains poorly understood. In the superman (sup) mutant, expression of APETALA3 (AP3) and PISTILLATA, which promote stamen identity, expands towards the center of the flower, and numerous extra stamens develop at the expanse of carpels. Although SUP was identified more than two decades ago, there are still two conflicting models to explain how SUP functions to maintain the boundary between stamens and carpels. The “homeotic model” postulates that formation of extra stamens in sup flowers results from a female-to-male change of identity of fourth whorl cells, associated with a prolonged maintenance of stem cells. Conversely, the “proliferation model” postulates that formation of these extra stamens results from an overproliferation of third whorl cells. I will discuss live confocal imaging experiments that demonstrate that (1) stem cells are maintained longer in sup mutant flowers than in the wild type, and (2) groups of cells in the central part of sup mutants flowers switch from not expressing AP3 to expressing AP3. Altogether, our data lends support to the homeotic model.