The organization of microtubules during generative-cell division in Convallaria majalis

The organization of the microtubule cytoskeleton in the generative cell of Convallaria majalis has been studied during migration of the cell through t he pollen tube and its division into the two sperm cells. Analysis by conve ntional or confocal laser scanning microscopy after tubulin staining was us ed to investigate changes of the microtubule cytoskeleton during generative -cell migration and division in the pollen tube. Staining of DNA with 4',6- diamidino-2-phenylindole was used to correlate the rearrangement of microtu bules with nuclear division during sperm cell formation. Before pollen germ ination the generative cell is spindle-shaped, with microtubules organized in bundles and distributed in the cell cortex to form a basketlike structur e beneath the generative-cell plasma membrane. During generative-cell migra tion through the pollen tube, the organization of the microtubule bundles c hanges following nuclear division. A typical metaphase plate is not usually formed. The generative-cell division is characterized by the extension of microtubules concomitant with a significant cell elongation. After karyokin esis, microtubule bundles reorganize to form a phragmoplast between the two sperm nuclei. The microtubule organization during generative-cell division in Convallaria majalis shows some similarities but also differences to tha t in other members of the Liliaceae.