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The isolation and characterization of the NADH-cytochrome b5 reductases (CbR) gene from Mortierella alpina 1S-4 and the purification of the CbR expressed in Aspergillus oryzae are described. It was found that the purified CbR used NADH but not NADPH as an electron donor. When NADH was utilized as the electron donor, DCPIP was observed to be reduced by the purified CbR. Results provide support for the hypothesis that the cDNA cloned is definitely a CbR gene.

A novel delta 5-desaturase defective mutant, S14, obtained from an arachidonic-acid generating fungus, Mortierella alpina, 1S-4, generates dihomo-gamma-linolenic acid (DGLA). Under favorable conditions, more than twograms of DGLA per liter of culture broth is generated by delta 5-desaturase-defective mutant. This is possible when it is developed for seven days in a 5-litre jar fermentor at 28 degrees Celsius under submerged batch culture conditions.

The overexpression of the diacylglycerol diphosphate phosphatase (DPP1) gene has promoted the production of (E,E,E)-geranylgeraniol (GGOH). The construction of diploid prototrophic strain coexpressing the hydroxymethylglutaryl-coenzyme A reductase (HMG1), geranylgeranyl diphosphate synthase (BTS1)-DPP1 and BTS1-ERG20 genes from multicopy integration vectors is described.

Agrobacterium tumefaciens-mediated transformation (ATMT) is examined for Mortierella alpina 1S-4 transformation by using the uracil-auxotrophic mutant of Mortierella alpina 1S-4 as a host strain and the homologous ura5 gene as a selectable marker gene. The ATMT system is effective and suitable for the industrial strain Mortierella alpina 1S-4 and is a useful tool for basic mutagenesis research and for industrial breeding of this strain.

The molecular characterization of the gene encoding sterol [DELTA]7 reductase from the fungus Mortierella alpina 1S-4 is presented. The molecular characterization of Mo[DELTA]7SR gene has helped in studying the steroid production by microbial fermentation, investigation of structure-function relationships in [DELTA]7SR and the elucidation of evolution of sterol reductases in various organisms.

The delta1-desturase gene was silenced in order to determine if RNA interference (RNAi) by double-stranded RNA occurs in Mortierella alpina IS-4. Thus RNAi occurs in M. alpina and could be used to alter the types and relative amounts of fatty acids produced by commercial strains of this fungus without mutagenesis or other permanent changes in the genetic background of the producing strains.