Explosive seed dispersal in Cardamine hirsuta

• Applicant: Dr. Erin Cullen
• Subject Area: Plant Cell and Developmental Biology ; Plant Genetics and Genomics
• Term: from 2021 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 462403708

Adaptations for dispersal are ubiquitous in nature. Plants have evolved many and varied ways to disperse their seeds, from the parachute of plumed dandelion seeds, to the exploding fruit of Cardamine hirsuta. 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 - seeds are accelerated from zero to ten metres per second in approximately half a millisecond! 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. Based on computational modelling, it was hypothesised that a viscoelastic ‘glue’ provides transient adhesion between the valve and seeds and determines seed ejection. In my project, I will investigate the genetic basis of seed ejection and link my findings with this viscoelastic model. Further, I will investigate how seed launch and seed dispersal is perturbed in a flightless (fli) mutant, where seed ejection is often unsuccessful. I will follow four objectives: (1) characterize the fli mutant in C. hirsuta and identify the responsible gene, (2) determine expression and function of the FLI gene product and how it relates to the model of viscoelastic seed launch, (3) analyse fli seed dispersal in the field and its response to environment, (4) compare FLI gene function in A. thaliana where seed dispersal is non-explosive. Using this integrated approach, I will identify the genetic and morphological basis of seed launch, and place it in an environmental context.

• DFG Programme: WBP Position