Regulation of Fructose Transport During Growth of Aspergillus nidulans

Abstract

Fructose transport by exponentially growing cultures of Aspergillus nidulans declines with culture age. The mechanism of age-dependent decline of transport capacity during exponential growth in liquid culture was studied in a mutant lacking fructokinase. The reduced ability of late cultures to transport fructose was not due to energy limitation as shown by measurements of intracellular ATP concentrations, nor was there a significant change in the apparent K m of early cultures compared with late cultures. Fructose transport was repressed by growth in glucose and derepressed by starvation. On the addition of glucose to derepressed cultures, fructose transport activity decayed. Comparisons of early and late cultures with respect to synthesis and degradation of the fructose transport system showed that the synthesis of a limiting component of the transport system was reduced in late cultures. The significance of these findings with respect to developmental scheduling is discussed.