IS THE RECOVERY OF MICROTUBULE ORIENTATION IN PEA ROOTS DEPENDENT ON THE CELL-WALL

This study tested several aspects of a model proposed by Williamson (1 990, 1991) in which stresses in plant cell walls, detected by stress-r eceptive portions of inelastic cellulose microfibrils, orient microtub ules via interactions with cell wall-linked transmembrane proteins. Yo ung expanding cells of pea root tips have highly ordered transverse ar rays of microtubules oriented perpendicular to the direction of cell e xpansion. The recovery of these ordered MT arrays after depolymerisati on with oryzalin was assessed. It was shown that treating roots with d isrupters of microfibril synthesis (2,6-dichlorobenzonitrile and calco fluor white) or the disruption of Arg-Gly-Asp (RGD)-mediated wall-memb rane links did not affect the orientation of recovering microtubule ar rays. Furthermore, cell wall stresses themselves appeared unnecessary for regeneration of transverse arrays. The relevance of these findings to Williamson's hypothesis is discussed.