Formation of Gamma Particles During Zoosporogenesis in Blastocladiella Emersonii

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Abstract
SUMMARY The formation of gamma (γ) particles was examined by electron microscopy of B. emersonii cells that were induced to differentiate zoospores after 15.5 hr (19-hr cycle) and 3 hr of growth (minicycle). In both the 19-hr and minicycle cells γ-particle formation began during the papillar stage when electron-dense granules 0.04 μm in diam with electron- transparent cores appeared inside ER cisternae. These granular “subunits” increased in number and presumably fused to yield doublet and triplet structures. Further coalescence of the 0.04-μm granules resulted in the formation of spherical aggregates 0.1 μ in diam which filled the smooth-surfaced cisternae containing them. During nuclear cap formation the 0.1-μm granules formed larger aggregates organized in ellipsoidal arrangements ca. 0.3 μm in diam. By the end of nuclear cap formation the 0.3-μm particles assumed the appearance of fully differentiated γ-particle matrices. The cisternal membranes of ER within which the 0.04-μm granules were first found were assumed to have transformed into the membrane surrounding the γ-particle matrix. The stages in the formation of the γ particle during zoospore differentiation are similar in both the 19-hr zoosporangial cycle and the minicycle.