Transformation system in the field of filamentous fungal hosts
A novel transformation system in the field of filamentous fungal hosts for expressing and secreting heterologous proteins or polypeptides is described. The invention also covers a process for producing large amounts of polypeptide or protein in an economical manner. The system comprises a transformed or transfected fungal strain of the genus Chrysosporium , more particularly of Chrysosporium lucknowense and mutants or derivatives thereof. It also covers transformants containing Chrysosporium coding sequences, as well expression-regulating sequences of Chrysosporium genes. Also provided are novel fungal enzymes and their encoding sequences and expression-regulating sequences.
1. A modified cell of a fungal strain derived from Chrysosporium lucknowense strain C1 (VKM F-3500 D), now classified as Myceliopthora thermophilum C1, comprising at least one nucleic acid sequence encoding one or more polypeptides,
wherein at least one nucleic acid sequence encoding one or more polypeptides is operably linked to one or more promoters operable in a fungal cell;
wherein zero or more of said nucleic acid sequences encoding one or more polypeptides comprise a sequence encoding a signal peptide fused in frame to a sequence encoding a polypeptide;
wherein said modified strain expresses one or more of said polypeptides at a higher level than a corresponding parental or non-modified strain under the same culture conditions.
2. The modified cell of a fungal strain of claim 1 , wherein said mutant is obtained by a method comprising introduction of at least one nucleic acid into a cell of said strain, wherein at least one nucleic acid comprises at least one heterologous sequence selected from the group consisting of a sequence comprising a promoter, a sequence encoding a signal peptide, and a sequence encoding a polypeptide.
3. The modified cell of a fungal strain of claim 2 , wherein said polypeptide is a heterologous polypeptide of plant, animal, algal, bacterial, archaebacterial, or fungal origin.
4. The modified cell of a fungal strain of claim 1 , wherein said polypeptide is a homologous fungal polypeptide.
5. The modified cell of a fungal strain of claim 1 , wherein said polypeptide is selected from the group consisting of carbohydrate-degrading enzymes, proteases, lipases, esterases, hydrolases, oxidoreductases, and transferases.
6. The modified cell of a fungal strain of claim 1 , wherein said polypeptide is selected from the group consisting of fungal enzymes allowing production or over production of primary metabolites, including organic acids, and secondary metabolites, including antibiotics.
7. The modified cell of a fungal strain of claim 1 , wherein said polypeptide is inactivated at a pH below 6.
8. The modified cell of a fungal strain of claim 1 , wherein said polypeptide is an enzyme that retains 70% or more of its activity in a buffered composition having a pH above 6.
9. The modified cell of a fungal strain of claim 2 , at least one nucleic acid comprises a sequence encoding a heterologous signal peptide.
10. The modified cell of a fungal strain of claim 1 , wherein said signal peptide is a fungal signal peptide.
11. The modified cell of a fungal strain of claim 10 , wherein the fungal signal peptide is a signal peptide obtained from a fungal polypeptide selected from the group consisting of a cellulase, a β-galactosidase, a xylanase, a pectinase, an esterase, a protease, an amylase, a polygalacturonase, and a hydrophobin.
12. The modified cell of a fungal strain of claim 1 , wherein said nucleic acid further comprises a sequence encoding a polypeptide conferring a selectable or screenable phenotype to said cell.
13. The modified cell of a fungal strain of claim 12 , wherein said phenotype is a selectable marker that confers resistance to a drug or relieves a nutritional defect.
14. The modified cell of a fungal strain of claim 1 , wherein said nucleic acid comprises one or more heterologous promoters.
15. The modified cell of a fungal strain of claim 1 , wherein said nucleic acid comprises one or more fungal promoters.
16. The modified cell of a fungal strain of claim 15 , wherein said promoter is an inducible promoter.
17. The modified cell of a fungal strain of claim 15 , wherein said promoter is a highly-transcribed promoter.
18. The modified cell of a fungal strain of claim 1 , wherein said mutant is obtained by a method of mutagenesis involving one or more steps selected from the group consisting of UV irradiation and chemical mutagenesis.
19. The modified cell of a fungal strain of claim 18 , wherein the method of mutagenesis comprises the steps of:
(a) treatment with UV irradiation;
(b) treatment with N-methyl-N′-nitro-N-nitrosoguanidine; and
(c) treatment with UV irradiation.
20. The modified cell of a fungal strain of claim 1 , wherein said fungal strain is a mutant derived from Chrysosporium lucknowense strain C1 (VKM F-3500 D), now classified as Myceliopthora thermophilum C1, selected from the group consisting of
C1 UV13-6 mutant deposited as accession number VKM F-3632 D, with a deposit date of Sep. 20, 1998,
C1 NG7C-19 mutant deposited as accession number VKM F-3633 D, with a deposit date of Sep. 20, 1998, and
C1 UV18-25 mutant deposited as accession number VKM F-3631 D, with a deposit date of Sep. 2, 1998.