A cDNA encoding delta 1-pyrroline-5-carboxylate reductase (P5CR) was isolated from the pneumocandin (Pmo)-producing fungus, Zalerion arboricola (Za), by complementation of a P5CR-deficient mutant (pro3) of Saccharomyces cerevisiae (Sc). The cloned cDNA was placed under control of the Sc galactokinase (GAL1) promoter and restored P5CR activity to the pro3 mutant. Sequence analysis revealed that the Za P5CR-encoding cDNA encodes an approx. 35 kDa protein with substantial amino acid (aa) identity to P5CR from another filamentous fungus, Neurospora crassa (Nc). Za P5CR exhibits a moderate degree of aa identity to P5CR from plants, bacteria, human and Sc. This is the first gene to be isolated from Za.