Protein Synthesis During the Differentiation of Sporangia in the Water Mold Achlya

Abstract

During the synchronous differentiation of sporangia in the absence of added nutrients, the water mold Achlya bisexualis (Coker and Couch) actively synthesized protein. Inhibition of protein synthesis at any time during the sporulation process completely inhibited further differentiation. Large changes in the rate of radioactive amino acid uptake resulted in changes in the specific activity of the cellular amino acid pool. The rate of protein synthesis was calculated from the amino acid pool specific activity and the incorporation of isotope into protein. During the 1st h after induction of the sporulation process, the rate of protein synthesis increased to two times the initial value. The amino acid precursors for this synthesis were supplied by the degradation of preexisting protein. Proteolytic enzyme activity assayed in vitro increased in proportion to the in vivo rates of protein synthesis and degradation. Differentiation was accompanied by a slight decline in dry weight of the mycelium as well as by a decrease in the protein content, whereas the relative size of the amino acid pools remained constant.

Growth and differentiation of the water mold Blastocladiella emersonii: cytodifferentiation and the role of ribonucleic acid and protein synthesis.

“…Starvation is a well-known method for inducing sporulation in a variety of aquatic fungi besides Blastocladiella (67, 230). In the case of Achlya bisexualis, the protoplasm of young, growthphase mycelia can be almost entirely converted into zoosporangia by starvation in 0.5 mM CaCl2 (94,247). The induction of differentiation in fungi by various degrees of starvation and many of the consequent metabolic responses are strikingly similar to the induction methods and responses reported for bacteria and cellular slime molds: the process of differentiation is characteristically an aerobic one, with accompanying changes in many of the enzymes of the tricarboxylic acid cycle, glyoxalate shunt, etc.…”

“…The only other aquatic fungus that has been studied in any detail for RNA and protein synthesis during differentiation is the oomycete Achlya (94,247). In this organism the differentiation of zoosporangia and zoospores requires about 5 h and, like Blastocladiella and Allomyces, the longest phase (To to T4) is required for conversion of the vegetative hyphal tips into septate zoosporangia.…”

“…The losses in total RNA and protein during Achlya sporulation were not considered significant by Griffin and Breuker (94) although both decreased by about 20%. With an improved induction system, Timberlake et al (247) reported that most of the mycelial cytoplasm was transferred to the developing zoosporangia. About 21% of the total protein was again lost, and these workers assessed the rates of protein synthesis, degradation, and turnover.…”

“…Nevertheless, even if one assumes a rate one-half that reported for Achlya, a large percentage of the amino acids released by degradation must be re-utilized at all stages. The high level of turnover is also accompanied by increased levels of protease activity (247), and development is inhibited by cycloheximide throughout.…”

The Selfinduced Metabolism of Antheridiol in Water Moulds

“…For hormone metabolism studies, mycelia were grown in 25 ml PYG medium (TIMBERLAKE et al 1973) in 100 ml flasks in a shaking water bath at 28°. Approximately 2 x 10-9 moles of radioactive steroid were added per flask and at various times the cultures harvested onto a Buchner funnel.…”