To molecularly characterize the influence of external pH in the secretion of enzymes by filamentous fungi, we have cloned and sequenced the palF gene of Aspergillus nidulans (An). An An wild-type (wt) chromosome VII-specific cosmid library was used to transform a palF15 mutant strain. Selection for complementation was done on medium containing beta-glycerolphosphate as the sole Pi source. Two cosmids were identified (W2G08 and W4G12) and further subcloning of one cosmid (W2G08) defined a 5-kb PstI genomic fragment, which fully complements the palF15 mutation. An internal fragment from the genomic clone recognized a single message of approx. 3.5 kb on Northern blot. cDNA clones were obtained from a lambda gt10 cDNA library and sequenced, showing a nucleotide (nt) sequence of 3311 base pairs (bp), with a 828 bp long 5'-untranslated region (UTR). The major open reading frame (ORF) identified in the sequence codes for a putative 775 amino acid (aa) protein, which shares some similarity with two putative ORF products of Saccharomyces cerevisiae (Sc).