Nucleocytoplasmic Interaction in the Eggs of Pteridium Aquilinum Maturing in the Presence of Thiouracil

Ultrastructural and cytochemical studies on oogenesis of the fern Pteridium aquilinum

Egg development in Pteridium aquilinum var. latiusculum was studied using ultrastructural and cytochemical methods to examine structural features influencing fertilization in leptosporangiate ferns. Ultrastructural observations indicate a separation cavity is first formed above the egg during oogenesis with a pore region persistently connecting the egg and the ventral canal cell. The egg envelope is formed by deposition of amorphous materials in the separation cavity on the outer surface of plasmalemma. The egg envelope was not formed across the pore region; instead, a fertilization pore was formed. During oogenesis, the egg nucleus produced extensive evaginations containing osmiophilic bodies. Cytochemical experiments revealed that the egg envelope displays strong periodic acid-Schiff reaction indicative of polysaccharides, with negligible Sudan black B staining for lipids, suggesting that the egg envelope is composed principally of polysaccharides, and not lipids. The present manuscript provides new insights into egg structure and development of Pteridium, including discovery and characterization of the fertilization pore and observations on the chemical nature of the egg envelope, thus contributing to the understanding of the cytological mechanism of the sexual reproduction of ferns.

Evidence for the association of acyl transferases with the production of nuclear evaginations in maturing eggs of the fern Dryopteris filix-mas

Utilizing the ability of free CoA to reduce ferricyanide, evidence is presented that acyl transferase activity is associated with the nuclear envelope in the maturing egg of the fern Dryopteris filix-mas. This activity is particularly marked in the nuclear evaginations. This strengthens the view that the evaginations are distinct structures formed by localized growth of the envelope, and not transient extensions of the nucleus.