Role of Glucose and Amino Acids in the Production of Resistant Sporangia by Allomyces macrogynus

Abstract

The selective production of resistant sporangia by A. f1Ulcrogynus required the presence of glucose and a suitable amino acid at the time of transcription of mRNA. Plants suspended in glutamate solution alone made zoosporangia only but the addition of glucose at various times permitted resistant sporangia to develop after 4-5 h, during which time glycogen and trehalose had accumulated to maximum levels. After septation of the resistant sporangium, adequate glucose was still required to complete the acid-resistant wall; otherwise the developing structure reverted to a zoosporangium. Plants suspended in glucose-ammonium citrate solution metabolized glucose without accumulating glycogen or trehalose for 8-9 h and produced only zoosporangia in this time. At and above 12 mM glucose a maximum content of glycogen and trehalose was reached although glucose was still available to the plants.

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

“…Measured over a period of 3 h 2 mM homo serine reduced the rate at which 4·5 mM glucose was utilized by 40%. The effect of this inhibition of glucose metabolism was similar to the effect observed previously of an exhaustion of the supply of glucose (Youatt 1982c).…”

“…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.…”

“…The completion of resistant sporangia requires the continuing presence of glucose until the acid-resistant wall has been completed (Youatt 1982c). The presence of trehalose may therefore have an indicator role that glucose is still available.…”

“…Whereas glycogen synthesis continued until glucose was exhausted, trehalose synthesis ceased at about 1 . 5 mM and trehalose was released to the medium (Youatt 1982c).…”

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

“…Selective production of resistant sporangia by A. macrogynus was observed in solutions which contained only glucose and sodium glutamate (Youatt 1980a). Although the control of differentiation was not complete, this combination permitted an investigation of biochemical changes in plants which developed either zoosporangia or predominantly resistant sporangia (Youatt 1980b(Youatt , 1980c(Youatt , 1982b. The development of resistant sporangia was preceded by increases in the plant content of trehalose, glycogen and phosphate esters.…”