McGill's Seminar Series in Quantitative Life Sciences and Medicine
Sponsored by CAMBAM, QLS, MiCM and the Ludmer Centre

Title: "Control of growth in plant cells through kinetic and mechanical microtubule organization"
Speaker: Eric Cytrynbaum (University of British Columbia)
When: Tuesday October 16 2018
Where: McIntyre Building, Room 1027

Abstract: In growing plant cells, parallel ordering of microtubules (MTs) along the inner surface of the cell wall/membrane influences the direction of cell expansion and hence  plant morphology in general. In stem and root cells, for correct expansion, MTs must bend in high-curvature directions along the cylindrically shaped cell wall/membrane in order  to form the required circumferential arrays. Previous studies, which recapitulated the self-organization of these arrays, ignored MT mechanics and assumed MTs follow geodesics of the cell surface. Here, we show, through analysis of a derived Euler-Lagrange equation, that an elastic MT constrained to a cylindrical surface will deflect from high to low curvature directions to minimize bending energy as it grows but only at low anchor density. At high anchor density, MTs follow geodesics. This result justifies the previous self-organization results for arrays in growing stem and root cells at high anchor density but predicts incorrect array orientation at low anchor density in those cells. It also provides a mechanism by which cells, in general, can regulate array orientation and hence growth and is consistent with experiments on mutant plants that have modified MT anchoring dynamics and misoriented arrays.