Colchicine-Induced paracrystals in root cells of wheat (Triticum Aestivum L.)

Abstract

Tubulin conformations other than microtubules in the meristematic cells of wheat roots grown in the presence of 2 mM colchicine solution were investigated by immunofluorescence and electron microscopy. In the affected cells microtubules disappeared and were replaced by tubulin fluorescent strands that occurred in the cortical cytoplasm. With increasing time of exposure to colchicine the tubulin strands became better organized and occurred also in the subcortical cytoplasm and finally they were restricted to the area around the nucleus. In prophase and preprophase cells thick strands occupied the cortical cytoplasmic zone where in normal cells a preprophase microtubule band (PMB) was expected to be assembled. In the colchicine-treated cells electron microscopy revealed an accumulation of paracrystalline aggregates, which initially occurred along the cell wall and later deeper in the cytoplasm, in the perinuclear regions and the cytoplasmic invaginations of the nucleus. In transverse planes the paracrystalline strands appear to consist of hexagonal subunits in a ’honeycomb’ arrangement, while in longitudinal and oblique sections they exhibit variable images. Since their distribution coincides with that of the tubulin strands visualized by immunofluorescence, they are considered to be the same structure. Therefore, the paracrystals consist of, or at least contain, tubulin. They are most likely to be polymers of tubulin-colchicine complexes. © 1995 Annals of Botany Company