Cruciform Nuclear Division in Sorosphaera Veronicae

Abstract

Sorosphaera veronicae Schroet. is an endobiotic, holocarpic, obligately parasitic fungus presently classified in the Plasmodiophoromycetes. The ultrastructure of nuclear envelope formation in somatic nuclear division in cystosoral plasmodia was studied. The inner membrane of the nuclear envelope during prophase appears to invaginate and blebb off intranuclear membranous vesicles. The intranuclear membranous vesicles become associated with the surface of the separating chromatin in anaphase and eventually are involved in the formation of daughter nuclear envelopes within the original nuclear envelope. The sequence of nuclear envelope breakdown and reformation in S. veronicae is noteworthy because it emphasizes alternate methods of nuclear envelope formation other than the generally considered “typical” formation described in Allium cepa L.