Figure 2.—

Properties of SN1, a hygromycin-resistant mutant strain of N. crassa. Strain CHZ10 has an integrated translational fusion containing the regulatory region and part of the coding region of con-10 fused to the coding region of the gene conferring resistance to hygromycin (hph). CHZ10 is sensitive to hygromycin under continuous exposure to light because the con-10 promoter is not active due to photoadaptation. Strain SN1 was derived from CHZ10 after UV mutagenesis. It grows in hygromycin-containing agar under constant light due to the increased accumulation of the con-10∷hph mRNA after light exposure. Conidia from CHZ10 or SN1 were grown in sorbose minimal agar or sorbose agar containing hygromycin (2 mg/ml) at 22° in the dark or under constant white light.