Fig. 6

Increase in cytosolic ROS level after Sr²⁺ addition. a Cytosolic ROS levels were detected using the specific fluorescent probe DCFH-DA. Trichoderma reesei RUT-C30 strain was cultured in liquid MM with SrCl₂ at a final concentration 0 or 70 mM for two days. To treat the hyphae, 10 μM DCFH-DA was used. The fluorescence intensity was monitored using automatic inverted fluorescence microscopy. Stronger green fluorescence indicated a higher intracellular ROS content. b Transcription levels of sod1 and cat1 were detected using RT-qPCR analysis, depicted as gene expression ratios [-fold] in RUT-C30 after treatment with 70 mM Sr²⁺ compared to RUT-C30 with no treatment on 1% Avicel for 48, 60, or 72 h. Gene expression ratios [-fold] were normalized to the corresponding gene expression at the same time point in the control (without Sr²⁺). The final values are represented as the mean ± standard deviation (SD) of three independent experimental results. Asterisks indicate significant differences, representing gene expression ratios greater than twofold or less than 0.5-fold between the treated samples and those without Sr²⁺ treatment. DIC, differential interference contrast; RT-qPCR, reverse transcription quantitative polymerase chain reaction