Professor & Canada Research Chair McGill University
To reach the female gametophyte, growing pollen tubes must penetrate different tissues within the pistil, the female reproductive organ of a flower. Past research has identified various chemotropic cues that guide pollen tubes through the transmitting tract of the pistil and towards a receptive ovule. It is thought that physical mechanisms also play a role in pollen tube guidance, but details of such a mechanism are unknown. Here we show that pollen tubes from plants with solid transmitting tracts actively respond to the stiffness of the growth substrate. We find that pollen tubes from Nicotiana tabacum and other plant species with a solid or semi-solid transmitting tract increase their growth rates in response to an increasing matrix stiffness. By contrast, pollen tubes from Lilium longiflorum and other plant species with a hollow transmitting tract decrease their growth rates with increasing matrix stiffness, even though the forces needed to maintain a constant growth rate remain far below the maximum penetration force these pollen tubes are able to generate. Moreover, when confronted with a transition from a softer to a stiffer matrix, pollen tubes from N. tabacum display a greater ability to penetrate into a stiffer matrix compared to pollen tubes from L. longiflorum, even though their maximum invasive force is smaller. These findings establish a previously unknown durotropic growth behavior that is only expressed in pollen tubes from plants with a solid or semi-solid transmitting tract and thus may contribute to an effective pollen tube guidance within the pistil.
Coauthors: Ronny Reimann – University of Erlangen-Nuremberg;Delf Kah – University of Erlangen-Nuremberg;Christoph Mark – University of Erlangen-Nuremberg;Jan Dettmer – University of Erlangen-Nuremberg;Theresa Reimann – University of Erlangen-Nuremberg;Richard Gerum – University of Erlangen-Nuremberg;Petra Dietrich – University of Erlangen-Nuremberg;Ben Fabry – University of Erlangen-Nuremberg;Benedikt Kost – University of Erlangen-Nuremberg