The γ-actin encoding gene from the β-carotene producer Blakeslea trispora

We determined the nucleotide sequence of a 4599-bp DNA genomic fragment including the γ-actin encoding gene from Blakeslea trispora, showing an open reading frame of 1561 bp interrupted by four introns with fungal consensus splice-site junctions. The untranslated regions of the actA gene contain a consensus TATA box, a CCAAT motif, a large pyrimidine stretch, and the polyadenylation sequence AATAAA. The predicted protein (375 amino acids) revealed high identity to γ-actins from fungi (>90%), and gene phylogenies support the grouping of B. trispora actin close to those from the majority of the filamentous fungi. actA transcript (1.4 kb) level in β-carotene producing conditions was faintly higher than carRA (1.9 kb) and slightly lower than carB (1.8 kb) β-carotene biosynthetic genes. The use of the actA promoter (PactA) for heterologous gene expression was ascertained by the transformation of gene fusions with the bleomycin resistance gene (bleR) from Streptoalloteichus hindustanus and the geneticin resistance marker (aphI) from Tn903, into Escherichia coli and Acremonium chrysogenum.