The zoospore of Rozella allomycis: ultrastructure

Abstract

The small (about 2 × 3.5 μm) zoospore of the obligately parasitic chytrid Rozella allomycis provides yet another ultrastructural variation on the basic pattern of posteriorly uniflagellate fungal zoospores. This zoospore contains the expected array of organelles: nucleus, mitochondria, "lipid sac" (including lipid globules, a microbody, and a backing membrane), kinetosome, and second centriole. Ribosomes are dispersed throughout the cytoplasm. In the disposition of its microbody Rozella resembles other chytrids, whereas in the occurrence and location of its gamma-like vacuoles it resembles certain blastocladialean fungi. Above all, the zoospore resembles that of Olpidium brassicae. Structural peculiarities of the zoospore include (i) bilateral symmetry; (ii) a helmet-shaped nucleus with extensive membranous projections which surmounts a large, spheroidal mitochondrion; and (iii) a particularly elongate cell shape because of the unusual length (about 1 μm) of the kinetosome and the presence of a 1-μm-long flagellar cavity which surrounds the base of the flagellum. Cytoskeletal elements include cytoplasmic microtubules, microfilaments which mainly reinforce the flagellar cavity, and props which anchor the kinetosome in the plasmalemma at the roof of the flagellar cavity. The role of these elements is discussed. A revision of the description of the olpidiaceous zoospore is suggested.

The Environmental Clade LKM11 and Rozella Form the Deepest Branching Clade of Fungi

“…Other features of Rozella spp. advocate for their placement into Fungi: flagellated zoospores with fungal-like ultrastructure of the flagellar apparatus (Held 1975), thick-walled resting spores and penetration of the host via a germ tube (Held 1973). Further prospecting on more representatives of the ''Rozellida'' will be crucial for circumscribing the true fungi.…”

Early evolution of eukaryote feeding modes, cell structural diversity, and classification of the protozoan phyla Loukozoa, Sulcozoa, and Choanozoa

“…The ancestral paramycian presumably was free-living with both a single cilium and filose pseudopodia. Unfortunately rozellid microtubular roots are little known, fixation for Aphelidium (Schnepf et al 1971) being unsuitable; one study on Rozella was scanty but revealed singlet microtubules radiating from the centrioles (Powell 1984); the other showed that the barren centriole is at 45 • to the ciliated one, which is connected by a double striated rhizoplast to a large, spheroidal mitochondrion abutting the helmet-shaped nucleus (Held 1975).…”

Development of Rozella in Allomyces: a single zoospore produces numerous zoosporangia and resistant sporangia

“…However, during previous work on the ultrastructure of Rozella zoospores (12) and of early steps in host invasion (7,9), I obtained some micrographs of the intracellular stages. Despite the fact that the material differs somewhat from that used in the present study (it represents multiple, uncontrolled infection, and the host is A .…”

“…Similarities in zoospore structure between R . allotnycis and several olpidiaceaous species in the genera Olpidi~ltn and Dictyotnorphn argue for maintaining it in the family Olpidiaceae ( 12).…”