DISTRIBUTION OF GAMMA-TUBULIN DIFFERS IN PRIMARY AND SECONDARY OOCYTES OF EPHESTIA-KUEHNIELLA (PYRALIDAE, LEPIDOPTERA)

In a previous study, barrel-shaped spindles were found in metaphase I oocytes of Ephestia kuehniella (Pyralidae, Lepidoptera). Aster microtu bules (MTs) were missing (Wolf, 1993: Cell Motil Cytoskeleton 24:200-2 04). This points to an acentriolar organization of the spindle apparat us. The present study was aimed at the question of whether gamma-tubul in, a newly detected member of the tubulin superfamily that has often been identified in microtubule-organizing centers, plays a role in the nucleation of MTs in meiotic spindles of the moth. To this end, the d istribution of gamma-tubulin was examined in oocytes of E. kuehniella using an antibody against gamma-tubulin in combination with indirect i mmunofluorescence. The antibody evenly decorated spindle MTs in metaph ase I oocytes of the moth. Enhanced staining of the spindle poles was not detectable. In subsequent stages of meiosis, gamma-tubulin was gra dually lost from spindle MTs and was then found at the surface of the so-called elimination chromatin. Female meiosis in Lepidoptera is achi asmatic. The elimination chromatin, i.e., modified and persisting syna ptonemal complexes, is believed to keep homologous chromosomes linked until the onset of anaphase I. In meiosis I of female Lepidoptera, the elimination chromatin per sists at the spindle equator between the se gregating chromatin masses. It is plausible to assume that gamma-tubul in is involved in spindle organization in the absence of canonical cen trosomes. In MTs of metaphase II spindles of E. kuehniella, gamma-tubu lin was no longer detectable with our immunological approach. This poi nts to a far-reaching change in spindle organization during transition from meiosis I to meiosis II. (C) 1996 Wiley-Liss, Inc.