The development of a heterologous transformation system for the cellulolytic fungus Trichoderma reesei based on a pyrG-negative mutant strain
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- Gruber, F., Visser, J., Kubicek, C.P. et al. Curr Genet (1990) 18: 71. doi:10.1007/BF00321118
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Six uridine auxotroph mutants of Trichoderma reesei QM 9414 were isolated by resistance to 5-fluoroorotic acid and one strain was identified as OMP-decarboxylase negative (pyr-) by a radiometric enzyme assay. Transformation to uridine prototrophy was achieved with the pyr4 gene of Neurospora crassa (up to 1500 transformants/μg) and with pyrA of Aspergillus niger (700–800 transformants/μg). In many transformants the PYR+ function seems to be present as extrachromosomal DNA. There is evidence for a correlation between the stability of transformants and integration of the vector in the genome whereas unstable transformants are obtained when autonomous replication of the plasmid occurs.