Liquid culture enhances protoplast formation from the auxotroph (ser(-)) ofLentinula edodes

Protoplast fusion betweenLentinula edodes andCoriolus versicolor

Protoplast fusion between isoleucine-, arginine- and thymidine-requiring auxotroph (lle, Arg, Thy) ofLentinula edodes and arginine-requiring auxotroph (Arg) ofCoriolus versicolor has been achieved using 30% polyethylene glycol (M.W. 4000) in 10 mMCaCl(2)-glycine solution (pH 8.0). Fusion hybrids were selected in the 0.6 M sucrose supplemented minimal media on the basis of nutritional complementation with fusion frequency of 7.4x10(-6). The hybrids included both parental and non-parental types in colony morphology, growth rate and isozyme patterns. We succeeded inter-order protoplast fusion between the auxotrophs ofLentinula edodes and Coriolus versicolor overcoming the natural barriers of incompatibility. We examined the characteristics of the hybrids and clarified the fusion process using electron microscopy.

Mycelial protoplast isolation and regeneration of Lentinus lepideus

Generation of fungal protoplast is essential for fusion and transformation systems. Protoplast fusion offers great potential for the improvement of industrially important microorganisms. To establish conditions for the protoplast isolation and regeneration of the mycelia of Lentinus lepideus, various enzymes and osmotic stabilizers were examined. To investigate suitable medium for the culture of L. lepideus, the mycelia were grown in ten different media at 28 degrees C for 10 days. Among them potato dextrose agar (PDA) medium was found to be the best for colony growth. When Novozym 234, cellulase and beta-glucuronidase were added to the mycelia in combination or alone, Novozym 234 alone at the concentration of 10 mg/ml was the most effective for the protoplast yield. Purified spherical protoplasts of the mycelia were osmotically hypersensitive and further incubation of the mycelia with the lytic enzyme resulted in the older parts of the hyphae swollen. When we applied various osmotic stabilizers at the fixed concentration of 0.6 M on the protoplasts, the yields of protoplasts were increased until 4-hr incubation. However application of sucrose or MgSO4 led to further protection of protoplasts after that time and reached a plateau on 5- and 7-hr incubations, respectively. The suitable incubation time and optimal pH with the lytic enzyme for the maximum release of protoplasts were 6 hrs of incubation and pH 5, respectively. When we examined various osmotic stabilizers for the regeneration of the protoplast, the complete medium containing 0.6 M sucrose induced highest hyphal growth with regeneration frequency of 3.28%.

Generation of nuclear hybrids overcoming the natural barrier of incompatibility: transfer of nuclei from Lentinula edodes into protoplasts of Coriolus versicolor

Heterokaryotic nuclear hybrids overcoming the natural barriers of incompatibility have been studied in basidiomycetes. To produce these nuclear hybrids between incompatible mushrooms, which have several potent pharmacological effects, nuclear transfer was performed between Lentinula edodes and Coriolus versicolor. Nuclei from serine auxotrophs of Lentinula edodes, LE207 (Ser-) were transferred into the protoplasts of arginine auxotrophs of Coriolus versicolor, CV17 (Arg-), using 30% polyethylene glycol 4000 in 10 mM CaCl2-glycine solution (pH 8.0). Nuclear transfer progenies were selected by nutritional complementation on minimal media supplemented with 0.6 M sucrose. The progenies were classified based on colony morphology to L. edodes-like, C. versicolor-like and non-parental type. Most of the progenies grew slower than either parent. The number of nuclei per cell was similar but the DNA content varied between progenies. The isozyme patterns of nuclear hybrids resembled either of the parent profiles or showed a mixed profile.