A high molecular weight polypeptide cross-reacting with the antibodies to the dynein heavy chain localizes to the subset of Golgi complex in higher plant cells.

Antibodies were produced against fragments of the microtubule-binding domain and the motor domain of the dynein heavy chain from Dictyostelium discoideum to probe whole cell extracts of root meristem cells of wheat Triticum aestivum. In plant extracts, these antibodies cross-reacted with a polypeptide of high molecular weight (>500kDa). The antibodies bound to protein A-Sepharose precipitated high molecular weight polypeptide from cell extracts. Immunofluorescence showed that the antibodies identified various aggregates inside cells, localized at the perinuclear area during interphase to early prophase, at the spindle periphery and polar area during mitosis, and in the interzonal region during phragmoplast development. Some aggregates were also co-labeled by markers for the Golgi apparatus. Thus, we found in higher plant cells a high molecular weight antigen cross-reacting with the antibodies to motor and microtubule-binding domains of dynein heavy chains. This antigen is associated with aggregates distributed in the cytoplasm in cell cycle-dependent manner. A subset of these aggregates belongs to the Golgi complex.

Time and cell cycle dependent formation of heterogeneous tubulin arrays induced by colchicine in Triticum aestivum root meristem.

We have investigated the appearance and reorganization of tubulin-containing arrays induced by colchicine in the root meristem of wheat Triticum aestivum, using immunostaining and electron microscopy. Colchicine caused depolymerization of microtubules and formation of tubulin cortical strands composed of filamentous material only in C-mitotic cells. After prolonged exposure to the drug, both interphase and C-mitotic cells acquired needle-type bundles, arranged as different crystalloids and/or macrotubules. The unmodified tyrosinated form of alpha-tubulin was detected within microtubules in control cells, but was not found within cortical strands. It was identified, however, within needle-type bundles. The modified acetylated form of alpha-tubulin, which was absent in control cells, was detected within needle-type bundles. Thus, cortical strands were transitory arrays, transformed into needle-type bundles during prolonged exposure to colchicine. Cortical strands appeared in a cell cycle-dependent manner, whereas needle-type bundles were cell cycle stable arrays. The diverse morphological organization, intracellular distribution and stability of tubulin-containing arrays may be associated with heterogeneity of alpha-tubulin isoforms. We assume that non-microtubular arrays substitute for microtubules in conditions where normal tubulin polymerization is inhibited.