Alumni Zoom Talk: Explosive Seed Launch in Cardamine hirsuta with Dr Erin Cullen

Plants have evolved a myriad of strategies to enable successful seed dispersal. For example, the winged diaspores of dandelions are carried by the wind, or in the case of Cardamine hirsuta the energy is generated by the plant itself, via explosive dispersal. Explosive seed dispersal in C. hirsuta is a rapid movement where elastic potential energy is stored in the fruit, released as kinetic coiling energy, and transferred to launch the seeds. This movement is so fast that high-speed cameras are needed to see the explosion. Cellular innovations have been identified that are responsible for generating and rapidly releasing tension in the exploding fruit. Yet it is unknown how the kinetic energy in the coiling valve is transferred to the seeds. To address this question, we identified a flightless (fliC. hirsuta mutant, in which seed launch often fails. We have mapped the underlying gene to ABCG32, a plasma-membrane bound transporter that transports hydrophobic cutin monomers out to the cell wall. fli exhibits a defective cuticle phenotype in both the seed and the side of the valve in contact with the seed. We propose that this may be the reason why seed launch fails in the fli mutant. Alternatively, the formation of a cuticle may be required for successful abscission between the seed and the funiculus (the structure which attaches the seed to the replum). The evidence supporting these alternative hypotheses will be discussed during the talk.