Pyruvate decarboxylase filaments are associated with the cortical cytoskeleton of asci and spores over the sexual cycle of filamentous ascomycetes

We show that pyruvate decarboxylase (PDC) 8- to 10-nm-diameter filaments, f irst described in vegetative cells of Neurospora crassa, are ubiquitously p resent in filamentous fungi, The cellular arrangement of these structures w as examined over the entire sexual cycle of the ascomycetes N, crassa, N, t etraesperma, Podospora anserina, and Sordaria macrospora, PDC-filaments wer e found associated with the cortical microtubule array of asci and ascospor es and absent from the vicinity of spindles and spindle pole bodies. Nocoda zole-induced depolymerization of the cortical microtubules results in the l oss of PDC-filaments, Moreover, a S, macrospora mutant defective in cortica l MT distribution shows abnormal PDC organization. Neurospora asci generate d on various metabolic conditions, which modify the presence and relative a bundance of PDC-filaments in vegetative cells, have identical patterns of s ubcellular distribution of these structures. A N, crassa mutant (snowflake) that accumulates giant bundles of PDC-filaments during vegetative growth, shows normal distribution of the filaments during ascogenesis. Thus, the re gulation conditioning the presence and supramolecular assembly of PDC-filam ents in Neurospora differs between vegetative and sexual cells. Taken toget her, these results suggest that PDC in filamentous fungi may perform two fu nctions, intervening as an enzyme in vegetative metabolism and as a structu ral protein associated with the cytoskeleton during sexual development, (C) 1999 Academic Press.