Meiosis and ascospore development in nonlinear asci of Neurospora pannonica

Abstract

Neurospora pannonica is homothallic, with 8-spored asci. Immature asci are usually swollen and noncylindrical while the mature asci are narrow and cylindrical. The two meiotic divisions resemble those of other Neurospora species. However, the orientation of third-division mitotic spindles and the distribution of nuclei in the swollen asci are irregular. Ascospores are arranged irregularly at first, but as the ascospores enlarge and mature the asci gradually become cylindrical, with the ascospores aligned in single file. The asci cannot be considered ordered tetrads, because ascospore order does not reliably reflect the assortment of chromosomes at the first and second meiotic divisions. Contrary to the original species description, ascospores require heat shock for germination and hyphae are sent out at both ends of germinating ascospores.

• ascospore dormancy
• ascus-shape
• homothallic Neurospora
• nonlinear asci
• unordered tetrads

I thank John C. Krug of the University of Toronto for the N. pannonica strain used in this study. The study was supported by NSF grant MCB-972876.