Ar. Mcdonald et al., GAMMA-TUBULIN IS ASSOCIATED WITH A CORTICAL-MICROTUBULE-ORGANIZING ZONE IN THE DEVELOPING GUARD-CELLS OF ALLIUM-CEPA L, Planta, 191(3), 1993, pp. 357-361
A key event in the differentiation of elliptically shaped guard cells
such as those in Allium is the formation of a radial array of cortical
microtubules (Mts) which, by controlling the orientation of wall micr
ofibrils, plays an important role in cell shaping. Previous experiment
s strongly indicated that the array is nucleated in a zone adjacent to
the new ventral wall soon after cytokinesis. In order to further clar
ify the function of this zone, we performed dual immunolocalizations o
n Allium guard cells with anti-beta-tubulin, to detect Mts, and an ant
ibody to gamma-tubulin, a protein known to be present at Mt-organizing
centers in other species and recently identified in plants as well. G
amma-Tubulin antibody stained the cortical zone adjacent to the ventra
l wall, while little or no fluorescence was present elsewhere along th
e radial Mt array or at other sites in the cell. The antibody also sta
ined the mitotic poles and phragmoplast in guard mother cells, as it d
oes in other material. No staining was seen when the primary antibody
was omitted. The results are consistent with nucleation of the radial
array at a cortical-Mt-organizing zone next to the ventral wall, and s
et the stage for more in-depth studies on the spatial and temporal con
trol of Mt formation in differentiating cells.