The mechanobiology of pollen penetration
Pollen grains deliver their sperm nuclei to the egg cells of the plant. To do so, the pollen grain grows a tube must pierce flower tissues. In this process, pollen tubes generate large mechanical forces to pierce tissues, and react to the mechanical responses of the tissue it is penetrating. We try to understand how pollen generate, perceive and respond to the forces involved in penetrative growth. We do so by combining biophysical approaches in bespoke microfluidic devices, quantitative imaging and cell biology.
After pollination, pollen, which carry the male reproductive cells, must deliver their content to the ovary of the plant to achieve fertilization. It does so by growing a tubular structure, which it uses as a penetration weapon that pushes itself through the tissue in the flower pistil, towards the ovary. During this process, the pollen tube must be strong enough to grow against a pressure that is similar to the pressure in a car tire or champagne bottle. This seems paradoxical since the tube also must soften its cell wall at the tip to enable itself to expand. This results in a complex mechanical conflict: a pollen tube must be soft and pliable to enable its growth, but simultaneously stiff and strong to generate sufficient forces to pierce the tissues in the flower. How pollen tubes solve this conflict is unclear; this is what we are trying to understand in this project.
In this project we will first develop new biophysical tools to quantify the mechanics of pollen tube invasion, and to enable the tunable mechanical challenging of pollen tubes during invasive growth. These assays consist of bespoke microfluidic devices, that contain matrices of different stiffnesses, and that enable the
quantitative imaging of mechanical force generation. We will then use a wide
variety of fluorescent marker lines and mutants with mechanical defects, to
understand how pollen tubes generate, perceive and respond to mechanical forces, down to the cell biological level.