Amino Acids in the Control of Differentiation of Sporangia in Allomyces macrogynus

Abstract

Of 24 amino acids tested all except glutamic and aspartic acids were able to block completely the transcription of mRNA for zoosporangium production of A. macrogynus within 30 min and for a period of at least 5 h at concentrations which were not excessively toxic. After 5 h terminal resistant sporangia developed with seven of the amino acids and zoosporangia with the others. The uptake, utilization and toxicity of amino acids were explored to explain the differences observed. Conditions for the controlled production of resistant sporangia were optimized for the glucose-leucine combination. Some amino acids were also able to inhibit zoosporangium development after mRNA transcription and before deposition of the septum. In the development of resistant sporangia stable mRNA was involved at least until the wall was acid-resistant. Synthesis of new mRNA was required to convert a developing resistant sporangium to a zoosporangium when the supply of glucose was inadequate.

Formation of O-Ethylhomoserine during the Controlled Production of Resistant Sporangia in Allomyces macrogynus

“…The two amino acids, aspartic and glutamic acids, which are not accumulated at high concentration in the amino acid pools, were unable to prevent the initial production of zoosporangia but both amino acids were favourable to later production of resistant sporangia. The ether was found at that time with these two amino acids as well as with arginine, asparagine, cysteine, histidine, glycine, leucine or valine used in the conditions described previously (Sandars and Youatt 1983). The ether has not been found in plants which were suspended in glucose with alanine, isoleucine, lysine, methionine, phenylalanine, serine, threonine, tryptophan or tyrosine tested over a range of concentrations.…”

“…The production of resistant sporangia correlates with the ability of amino acids to inhibit the production ofzoosporangia (Sandars and Youatt 1983) with the production of O-ethylhomoserine and with the presence of trehalose (Youatt 1982c). The question therefore arose as to why suspensions supplied with glucose and O-ethylhomoserine did not produce resistant sporangia sooner than 8-9 h since adequate concentrations of the.…”

“…Culture methods have been described previously (Youatt I 980a) and the bulk medium used was described by Sandars and Youatt (1983). Extraction of amino acid pools, trehalose and glycogen were described by Youatt (l980a) and assay procedures for carbohydrates by Youatt (1980b). 0004-9417/83/050497$02.00…”

“…In the study of the role of amino acids (Sandars and Youatt 1983) the requirements for the production of resistant sporangia were defined. In all conditions which allowed the development of resistant sporangia O-ethylhomoserine was detected and, except at trace concentrations, was detected in no other conditions.…”

“…The amino acid was obtained after plants had been incubated for 6-8 h with glucose and amino acids favourable to the formation of resistant sporangia (Sandars and Youatt 1983). Approximately 2 mg of material was isolated by paper chromatography using 80% (wjv) phenol and subsequently butanol-acetic acid solvents.…”