Sulphur Metabolism of Puccinia graminis f.sp. tritici in Axenic Culture

Abstract

SUMMARYAxenic cultures of Puccinia graminis f. sp. tritici cannot reduce sulphate for sulphur-amino-acid synthesis. Although [35S]sulphide is incorporated into these amino acids, the fungus still has a nutritional requirement for a sulphur amino acid. Most of the incorporated sulphide was found in the culture filtrate in the form of cysteine, S-methylcysteine, glutathione and cysteinylglycine. There were appreciable amounts of labelled methionine in mycelial protein but very little of this amino acid appeared in the culture filtrate. The results indicate that the nutritional requirements for sulphur amino acids by the rust fungus is caused by loss of cysteine and some of its derivatives into the medium.