Format: ORAL

Haoran Xue1, Kelly Shepherd2, Oliver Marketos2, Olivia Page-Macdonald2, Caroline Robertson2, Christian Kappel1, Robert Ingle2, Nicola Illing2, Michael Lenhard1

1 University of Potsdam, Potsdam, Germany 2 University of Cape Town, Cape Town, South Africa

Telling left from right is a difficult task for organisms, as the two sides can only defined by reference to two other axes. While genetically encoded left-right asymmetry is found in many animals, it is very rare in plants. One example is the mirror-image flowers of Wachendorfia and Barberetta. Species of these two closely related genera show enantiostyly, i.e. they form flowers with the style deflected to the left of the midline and one of the three stamens to the right, or with the opposite arrangement. All flowers on one individual have the same handedness, indicating genetic control. Functionally, the reciprocal placement of the stigma and the opposing anther promotes pollen placement on segregated sites of the pollinators bodies and efficient transfer to stigmas of the opposite morph. We are investigating the genetic, molecular and developmental basis of mirror-image style and stamen deflection in Wachendorfia and Barberetta. Genome assemblies and pooled sequencing of left- and right-morph individuals from natural populations have identified a hemizygous region whose presence causes right-styled flowers, whereas plants lacking this region form left-styled flowers. This region contains two conserved genes throughout all the species tested, one of which is expressed in the developing stamen, the other in the style around the time when the organs begin to deflect from the midline. Efforts to assign functions to these genes are ongoing. Identification of the hemizygous region opens up the possibility of assaying realized mating patterns in natural populations and testing the efficiency of enantiostyly in promoting disassortative mating. Thus, our results pave the way for a mechanistic understanding of left-right asymmetry in plants and its impact on plant reproduction.