MICROINJECTION OF FLUORESCENT TUBULIN INTO PLANT-CELLS PROVIDES A REPRESENTATIVE PICTURE OF THE CORTICAL MICROTUBULE ARRAY

By microinjecting rhodamine-labelled tubulin into living plant cells, it is possible to observe microtubules (MTs) directly and to see how t he cortical array reorganizes itself. The validity of the conclusions drawn from such observations depends upon the assumption that most, if not all, of the native MTs are dynamic and incorporate labelled tubul in. However, if arrays also contain Mis that are not exchanging tubuli n subunits, such MTs will remain unlabelled, and the labelled MT popul ation will be under-representative of the whole array. To address this potential problem, we microinjected pea epidermal cells with rhodamin e-labelled tubulin, then fixed the cells and used fluorescein-conjugat ed antibodies against tubulin to detect the entire MT array. The two f luorescent patterns corresponded well, confirming that the MTs labelle d with exogenous tubulin were evenly distributed throughout the entire array. Also, by comparing the MT image before and after aldehyde fixa tion, we observed that, although some of the MTs were lost in the proc edure, the fixation was able to preserve the arrangement of MTs seen i n the living cell. We conclude that fluorescence analogue cytochemistr y provides a valid representation of the entire cortical MT array.