Reorganization of cortical microtubules during cell differentiation in tobacco explants

Abstract

Using indirect immunofluorescence on polyethylene glycol embedded material, the organization of cortical microtubules (MTs) has been studied in explants ofNicotiana tabacum. Within 6 hours after explantation the orientation of the cortical MTs shifts from transverse to longitudinal to the long axis of the cell in all cells. This change of direction is followed by further shifts that occur only locally and predict the orientation of future cell divisions. These reorientations are independent of the formation of protrusions and buds that will develop in the explants (after 4–7 days) and they represent a stage of de-differentiation of the explants. After two days of culturing clusters of cells can be recognized, at the proximal side of the explants, with randomly oriented cortical MTs. These regions represent the origin of the protrusions from which floral buds will develop. The formation of these clusters represent the first signs of re-differentiation and formation of new polar axes in the explants. The cells thus show a very early commitment (within 2 days) as to their differentiation.