BETAINE TRANSPORT IN FUSARIUM-GRAMINEARUM

Fusarium graminearum A3/5 was found to possess a high-affinity transpo rt system (K(m) = 48 +/- 6 mum, V(max) = 8.9 +/- 0-7 nmol mg-1 dry wei ght min-1) for betaine which was energy-dependent and constitutive. Gl ucose-starved mycelia showed a reduced uptake, whilst nitrogen-starved mycelia increased the rate of uptake 2.8-fold over a 3 h period. The uptake system was highly specific for betaine, with only betaine aldeh yde and dimethylglycine competing with betaine transport. Choline had no effect on the rate of betaine uptake.