Fig. 3

Physiological function of lraA/AN4186 in l-rhamnose catabolism. a l-Rhamnose dehydrogenase activity: increase in absorbance at 340 nm upon incubation of l-rhamnose with cell free extracts of untransformed lraA⁺ (AR198) and ΔlraA (AR247 and AR248) strains in the presence of NAD⁺ at 37 °C. b Expression of lraA in the biA1 wild type control strain AR5 under different growth conditions: RT-sqPCR of RNA isolated from mycelia obtained 3 h after transfer to media lacking a carbon source (non-inducing/non-repressing conditions), 0.1% fructose (i.e. the pre-growth conditions), 2% lactose (non-inducing), 1% l-rhamnose (inducing), 1% glucose (repressing), and 1% l-rhamnose + 1% glucose (R + G inducing/repressing). The actin actA gene was used as a constitutive expression control for normalization. Amplifications (PCR) were reduced to 24 (actA) and 25 (lraA) cycles in order to obtain semi-quantitative data. PCR amplifications of gDNA are shown. M, low molecular weight marker (base pairs). c Deletion of lraA/AN4186 dramatically affects the production of α-l-rhamnosidase activity: extracellular α-l-rhamnosidase activities in lraA⁺ (AR198 and the isogenic nutritional control AR271) and ΔlraA (AR247 and AR248) strains 48 h after transfer to inducing conditions (1% l-rhamnose). Average activities and standard deviations of duplicates of two independent biological experiments are presented as percentages of those observed in AR198