Explosive seed dispersal in Cardamine hirsuta
Plant Genetics and Genomics
Final Report Abstract
Seed dispersal is essential for plant reproductive success. Plants have evolved innovative strategies to disperse their seeds. For example, dispersal in Cardamine hirsuta is explosive. Seeds are accelerated as fast as ten metres per second and dispersed within a two metre radius by C. hirsuta. This contrasts to the closely related Arabidopsis thaliana, which exhibits non-explosive dispersal. Previous work in C. hirsuta found that a mechanical instability in the fruit was responsible for generating the energy needed for explosive dispersal. However, the mechanism of seed launch is unknown. In this project, I aimed to use forward genetics and advanced microscopy to dissect the mechanism of seed launch in C. hirsuta. I characterised a flightless (fli) mutant, where the fruit explodes, but seed launch often fails. I showed through complementation analysis that ABCG32, a plasma-membrane bound transporter that transports hydrophobic cutin monomers, underlies the fli phenotype. fli exhibits a defective cuticle phenotype in both the seed and the side of the valve in contact with the seed. By TEM, I observed perforations in the seed coat cuticle. I propose that this may be the reason why seed launch fails in the fli mutant. Transcriptional reporters show that FLI/ABCG32 is expressed in the epidermis of aerial organs, including the valve, seed and funiculus of C. hirsuta fruit. RNAseq analysis indicates that cutin and wax biosynthesis pathways are perturbed in these tissues in the fli mutant, possibly to compensate for loss of cutin monomer transport. Overall, this work suggests that an intact cuticle is essential for explosive seed launch.
Publications
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Creating an explosion: Form and function in explosive fruit. Current Opinion in Plant Biology, 79, 102543.
Cullen, Erin & Hay, Angela
