Septal involvement in nuclear migration inSchizophyllum commune

Abstract

Summary.A system, utilizing the dwar] and pu/] morphological mutants of Schizophyllum commune, was devised to select specific hyphal segments that were in different stages of septal dissolution and nuclear migration. These stages were observed with the electron microscope. Direct evidence of the dissolution of complex septa during nuclear migration was obtained. Initially there was a disruption of the septal swelling, followed by erosion of the remaining cross wall. Complex septa were thereby converted to si~aple septa through which nuclei migrated. These septa were covered with secondary cell wall material. Following nuclear migration only vacuolate hyphae with remnant membrane structures remained. Occasionally, intact hyphae were observed within these vacuolate hyphae.The morphogenetic events in Schizophyllum commune, regulated by the A and B incompatibility fac.tors, have been extensively investigated (Raper and Raper, 1968). Following the fusion of hyphae of compatible mating types, and prior to the formation of basidiospore-bearing fruiting bodies, the vegetative hyphae undergo several changes leading finally to a fertile heterokaryon. These changes include nuclear migration, nuclear pairing, conjugate division, hook cell formation, septation of the apical cell along with the hook cell, and the fusion of the hook cell with the penultiniate cell. Nuclear migration, first described by Buller (1931) in Coprinus lagopus, has recently received much attention. It has been genetically demonstrated that the complete genome migrates through the hypha rather than pieces of genetic material (Snider, 1963). Since homokaryotie as well as dikaryotic hyphae contain complex septal pore structures (Jersild et al., 1967), the migrating nucleus must overcome these barriers. Giesy and Day (1965) reported simple septa and complex septa in different stages of dissolution in hyphae of C. lagopus in which nuclear migration was believed to have taken place. A similar series of events in a B-mutant of S. commune was described by Koltin and Flexer (1969).A bbreviations: IHW = intra-hyphal wall; mvb = multivesicular body; N = nucleus; pcs ~ pore cap structure; rms ~ remnant membrane structure; s = simple septum; ss =septa! swelling; sp = septal plug. 8*

Structural differences between two types of basidiomycete septal pore caps

“…sporotrichoides and S. commune has been repeatedly studied after chemical fixation (e.g. Guiho et al, Jersild et al, 1967;Mayfield, 1974;Moore & Patton, 1975;Van der Valk et al, 1977). GuCho et al (1992) reported that the SPC was almost absent in T .…”

“…The ultrastructure of the SPC of T. sporotrichoides and S. commune has been repeatedly studied after chemical fixation (e.g. Guého et al ., 1992; Jersild et al ., 1967; Mayfield, 1974; Moore & Patton, 1975; Van der Valk et al ., 1977). Guého et al (1992) reported that the SPC was almost absent in T. sporotrichoides and was present only as remnants of ER opposite the entrance of the septal pore channel.…”

Tetrapolar fungal mating types: Sexes by the thousands

“…The process of nuclear migration is under investigation in different species [74][75][76][77]. After septal dissolution the newly built septa are simple, not of the dolipore type [78][79][80][81]. Because of dependence of the observed nuclear migration on the cytoskeleton, tubulin genes have been investigated.…”

Reproductive Biology of Fungi

“…No information is available about the factors controlling nuclear motility. Mayfield (1974) noted that nuclear. migration is accompanied by flow of cytoplasmic organelles, so that the hyphae become highly vocuolated.…”