Formation of Gamma Particles during Zoosporogenesis in Blastocladiella emersonii

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.