KATANIN-dependent mechanical properties of the stigmatic cell wall regulate pollen tube pathfinding

Successful fertilization in angiosperms depends on the proper trajectory of pollen tubes through the pistil tissues to reach the ovules. Pollen tubes start their path by progressing within the cell wall of the papilla cells, applying pressure to the wall. Mechanical forces are known to play a major role in plant cell shape by controlling the orientation of cortical microtubules (CMTs), and hence deposition of cellulose microfibrils (CMFs). Here, by combining cell imaging and genetic approaches, we show that isotropic orientation of CMTs in aged, katanin1-5 (ktn1-5) or oryzalin-treated papilla cells is accompanied by a tendency of pollen tubes to coil around the papillae. In addition, using atomic force microscopy, we uncover that aged and ktn1-5 papilla cells have a softer cell wall. Altogether, our results suggest that KATANIN-dependent control of microtubule dynamics, and associated mechanical anisotropy of stigmatic walls, mediate pollen tube growth directionality.