Biosynthesis of some Amino-Acids from Sucrose by Germinating Uredospores of Wheat Stem Rust, Race 15B

[Host-parasite metabolic relationship between puccinia graminis var. tritici and triticum vulgare (wheat) : I. Uptake of amino acids from the host]

Rust infected wheat plants were incubated with different (14C)-labelled amino acids. Uredospores that were formed during the incubation contained (14)C-activity. By analysis of these spores it was investigated whether the parasitic mycelium of Puccinia graminis takes amino acids from the host. It could be demonstrated that the applicated amino acids were taken up directly from the wheat leaf. The carbon sceletons of applicated lysine and arginine showed only little randomization of (14)C-activity. Glutamic acid, alanine and glycine isolated from uredospore protein showed a very strong alteration of the original label. The pools of free amino acids in the host and the parasite are in isotope equilibrium. This demonstrates, that synthesis of amino acids in the mycelium is quantitatively not important. By following the kinetics of incorporation of an amino acid it could be demonstrated that the amino acids enter the parasite as free amino acids and not in the form of proteins.

USE OF GLUTAMIC ACID-U-C14TO DETERMINE NUTRITIONALLY ESSENTIAL AMINO ACIDS FOR LARVAE OF THE BLOW FLY, PHORMIA REGINA

The production of C14O2by third-instar larvae of the blow fly, Phormia regina Meig., after it was injected with glutamic acid-U-C14, indicates that this substrate was metabolized under these conditions. However, the nutritionally essential amino acids lysine, phenylalanine, valine, isoleucine, leucine, and threonine, isolated from the injected larvae, contained little radioactivity. A low level of radioactivity in arginine, histidine, and methionine suggests that they were slowly synthesized. The nutritionally non-essential amino acids alanine, serine, aspartic acid, and proline contained large quantities of radioactivity; tyrosine and glycine were exceptions. These results, in agreement with earlier work that used glucose-U-C14, show that radioactivity data are useful for determining certain of the nutritionally essential amino acids.