KINETICS OF MESSENGER-RNA AND PROTEIN-SYNTHESIS OF GENES CONTROLLED BY THE 1,4-BETA-ENDOXYLANASE-A PROMOTER IN CONTROLLED FERMENTATIONS OF ASPERGILLUS-AWAMORI

In this study, induction and repression kinetics of the expression of the Aspergillus awamori 1,4-beta-endoxylanase A (exlA) gene under defi ned physiological conditions was analyzed at the mRNA and the protein levels, Induction was analyzed by pulsing D-xylose to a sucrose-limite d continuous culture of an A. awamori 1,4-beta-endoxylanase A (EXLA)-o verproducing strain, Directly after the D-xylose pulse, exlA mRNA was synthesized, and it reached a constant maximal level after 45 to 60 mi n. This level was maintained as long as D-xylose was present. The kine tics of mRNA synthesis of the genes encoding Thermomyces lanuginosa li pase (lplA) and Escherichia coli beta-glucuronidase (uidA), which were also under the control of the exlA promoter, were similar to those ob served for exlA mRNA, The repression of exlA expression was analyzed b y pulsing D-glucose to a D-xylose-limited continuous culture. Immediat ely after the glucose pulse, the exlA mRNA level declined rapidly, wit h a half-life of approximately 20 to 30 min, and it reached a minimal level after 60 to 90 min, The time span between mRNA synthesis and the secretion of proteins was determined for EXLA and lipase, In both cas es, mRNA became visible after approximately 7.5 min, After 1 h, both p roteins became detectable in the medium but the rate of secretion of E XLA was faster than that of lipase.