Lysine Synthesis in Rust Infected Flax Cotyledons

Abstract

Pathways of lysine biosynthesis in rust infected flax cotyledons have been investigated. Non infected cotyledons were shown to possess enzymes of the diaminopimelic acid pathway of lysine synthesis, but these enzymes could not be detected in axenic cultures of the flax rust fungus. Feeding experiments demonstrated the incorporation of diaminopimelic acid into lysine by the host but not by the fungus. Conversely, enzymes of the aminoadipic acid pathway of lysine synthesis are present in the rust fungus, but, with the exception of aminoadipate transaminase, not in non-infected cotyledons. Aminoadipic acid stimulated lysine production by the fungus but not by the host. Cotyledons infected for 7 days were shown to possess enzymes of both pathways, and seemed able to convert both diaminopimelic acid and aminoadipic acid into lysine. We consider these studies to demonstrate that infected flax cotyledons possess the ability to synthesize lysine by either pathway. The fungus may thus be capable of synthesizing at least some of the lysine it requires.