FIG. 2.

Northern blot analysis with total RNA from expression of A. niger genes encoding cellulose- and xylan-degrading enzymes. Time courses of induction of A. niger NW197 (ΔxlnR xlnR deletion mutant), N402 (wild type [wt]), and N902::pIM230-3.9 (xlnR⁺; 10 copies of xlnR) are shown. All three strains were cultured for 18 h in 3% (wt/vol) d-fructose, and mycelia were subsequently transferred to 25 mM sorbitol, 25 mM sorbitol plus 1 mM d-xylose, or 25 mM sorbitol plus 1 mM sophorose. Blots were hybridized with gene-specific probes as indicated and with an 18S rRNA probe as the loading control. The arrows indicate low but detectable hybridization signals.