Ultrastructure and behaviour of the spindle pole body of the aphid-pathogenic fungus Erynia neoaphidis.

A detailed account of the ultrastructure and behaviour of the spindle pole body (SPB) of the entomophthoraceous fungus Erynia neoaphidis is presented for the first time. The SPB consists of extranuclear (ENC) and intranuclear (INC) components. The ENC is a 'saucepan-shaped' structure which lies in a pocket of the nuclear envelope. It is composed of a forked, fibrillar 'handle' and a shallow, cylindrical 'pan'. The 'pan' has a wall of two layers, both of which are thickened with a regular periodicity so that they appear to be 'beaded'. It is postulated that the 'pan' is formed from rough endoplasmic reticulum and that it synthesizes the amorphous, electron-dense material coating the ENC. The INC is a 'saucer-shaped', electron-dense plaque in which the ends of the spindle microtubules terminate. During metaphase, a 'clear zone' separates the INC from the nuclear envelope and persists until telophase. The roles of the amorphous, electron-dense material and the 'clear zone' as well as the method of SPB replication are discussed. [ABSTRACT FROM AUTHOR]