Metabolism of glucose-14C, pyruvate-14C, and mannitol-14C by Melampsora lini. I. Uptake

Abstract

Aerial mycelium of the flax rust fungus (Melampsora lini (Pers.) Lév.) was grown on infected flax cotyledons in tissue culture. The endogenous respiration of detached mycelium varied from 1.5 to 4.8 μl/h per milligram dry weight, with a mean value of 2.6 ± 1.0. There was a significant negative correlation between respiration rate and percentage dry weight (r = −0.832; P < 0.025). The respiration of mycelium stored for longer than 10 h after excision was stimulated by the addition of glucose; such stimulation was not obtained consistently with freshly collected mycelium.The production of 14CO2 and the disappearance of radioactivity from the medium were measured at intervals during incubation of mycelium with glucose-1- and -6-14C, sodium pyruvate-1-, -2-, and -3-14C and mannitol-1-6-14C. Evidence was obtained that glucose is oxidized in the Embden–Meyerhof and pentose phosphate pathways and that pyruvate is oxidized via acetyl CoA and the tricarboxylic acid cycle. Rapid utilization of pyruvate- and mannitol-14C was preceded by a lag period of 4 to 9 h. The results are discussed in relation to the suitability of aerial mycelium for the study of rust metabolism.