UPTAKE AND METABOLISM OF [C-14] ASPARTATE IN BARLEY LEAVES INFECTED WITH POWDERY MILDEW

Infection of barley with powdery mildew altered the uptake and metabolism of [C-14]aspartate in first leaves. Uptake was greater in infected leaves 2h after feeding, but was reduced thereafter. Aspartate was more rapidly metabolised in infected leaves than in controls, probably to homoserine and threonine. The fungus took up aspartate, homoserine and threonine from the plant, but these were apparently not further metabolised over the experimental period. This suggests that barley can metabolise aspartate, probably forming homoserine, threonine and lysine, while such metabolism does not occur in the powdery mildew fungus. This would confirm the presence of the diaminopimelic acid pathway for lysine biosynthesis in barley and its absence from Erysiphe graminis f. sp. hordei Marchal.