Intergeneric Protoplast Fusion between Rhizopus oryzae and Aspergillus oryzae

Rhizopus oryzae와 Aspergillus oryzae의 속간 원형질체융합

Conditions for the release and regeneration of protoplasts form Rhizopus oryzae and intergeneric protoplast fusion between Rhizopus oryzae and Aspergillus oryzae were studied. High yields of protoplast fusion between Rhizopus oryzae and Aspergillus oxyzae were studied. High yield of protoplasts from young germilings of R. oryzae were obtained by using lytic enzymes containing chitosanase (3 mg/ml), chitinase (3 mg/ml) and Novozym 234 (5 mg/ml). 0.5M glucose was used as the osmotic stabilizer and optimum pH of buffer was determined to be pH 7.5-8.0. Under these conditions, protoplasts were formed after about 3-4 hrs incubation. Approximately, 1.0%-4.9% of these protoplasts were formed after about 3-4 hrs incubation. Approximately, 1.0%-4.9% of these protoplasts regenerated on solid medium with a soft agar overlay. We have also carried out protoplasts fusion between R. oryzae and A. oryzae and have succeeded in obtaining three types of intergeneric fusants. In these experiments, 35% PEG-4000 and 10 mM CaCl$_{2}$ were used as fsogenic agents, and auxotrophic properties were used as a genetic marker to select fusants. Complementation frequency be protoplasts fusion of A. oxyzae and R. oryzae was 4.4% * 10$^{-5}$ . The fusant strains of the first type were prototrophs showing an Aspergillus type morphology with dark-yellow sporulation, those of the second type were also Apergillus type morphology but showed no sporulation. And the strains of the third type stopped growing when fusion products grown on regeneration minimal medium were transferred to fresh minimal medium. The formation of fusion products was observed by fluorescent vital stains for complementary labelling of protoplats from R. oryzae and A. oryzae. Rhodamine 6G and fluorescein diacetate wer useful complementary vital stains of Rhizopus and Aspergillus protoplasts for visualization of requency and type (dicell, multicell) of fusion.