Formation of Gamma Particles during Zoosporogenesis in Blastocladiella emersonii

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