Preparation and regeneration of mycelial protoplasts of Collybia veltipes and Pleurotus ostreatus

Formation and regeneration of protoplasts in Sclerotium rolfsii ATCC 201126

AIMS

Different cultural conditions for forming and reverting protoplasts were systematically studied to establish a rapid and efficient protocol for Sclerotium rolfsii ATCC 201126.

METHODS AND RESULTS

Osmotic stabilizer, lytic enzymes and mycelial age were the main factors influencing protoplast yields. An optimized protocol involving 1-h hydrolysis of 45-h-old mycelium with Trichoderma harzianum enzymes in a 1 : 1 (w/w) biomass : enzyme ratio and 0.6 mol l-1 MgSO4 as osmotic stabilizer was designed to produce approx. 2 x 109 protoplasts per gram biomass dry weight, with 99% viability. Differences on the lytic activity between batches of commercial enzymes were clearly evidenced. Protoplast release was highly efficient showing no remaining cell wall material as witnessed by fluorescent brightener 28. Up to 26% of purified protoplasts developed into the typical filamentous form after 50 h of incubation on 0.6 mol l-1 sucrose agar media.

CONCLUSIONS

The methodology herein proposed allowed a rapid, inexpensive and efficient protoplast production. Optimum yields were higher or in the order of that elsewhere reported for other S. rolfsii strains and the required lytic time was significantly shorter. Purified protoplasts successfully reverted to the filamentous morphology.

SIGNIFICANCE AND IMPACT OF THE STUDY

The present research reports the former protocol for the isolation and reversion of protoplasts in S. rolfsii ATCC 201126 providing key factors to ensure optimum results. In addition, the described procedure constitutes a starting point for downstream genetic manipulation.

Production and regeneration of protoplasts from Gremmeniella abietina and Ascocalyx abietis

This work was undertaken to develop a system of protoplast isolation and regeneration for G. abietina and A. abietis that could be of use for the genetic manipulation of both species. Nuclear staining was performed to assess the nuclear conditions of the protoplasts. Of the 19 enzyme complexes studied, only 10 were found to have some lytic effect on either Gremmeniella, A. abietis, or both. Only snail enzyme (from Szeged University), Novozym 234, lytic enzyme L1, or mixtures of snail enzyme and Novozym 234 produced satisfactory yields of protoplasts. Regeneration of protoplasts was observed on complete and on minimal medium, and occurred from protoplasts plated out directly onto the surface and from those embedded in the agarose. In most cases, embedding increased the frequency of regeneration. Protoplasts formed after incubation at 20 degrees C regenerated at a frequency of approximately 5%, as opposed to 2% for those produced at 30 degrees C. As roughly 40% of the protoplasts were anucleate, the percentage of regeneration can be estimated as about 12.5% at 20 degrees C and 5% at 30 degrees C. Protoplasting appears to be a satisfactory method of obtaining material for genetic experiments with G. abietina and A. abietis when other methods are not directly applicable.

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

The optimal conditions for the production and regeneration of the protoplasts fromLentinula edodes were studied. Protoplast formation from the mycelia ofL. edodes which were cultured in liquid medium showed a significantly high yield compared with that of the mycelia which were cultured on cellophane covered agar media. A mixture of Novozyme 234 (15 mg/ml) and Cellulase Onozuka R10 (10 mg/ml) in 0.6 M mannitol (pH 4) was optimal lytic enzyme for the protoplast release. The optimal incubation time and mycelia age were 3.5-4 hours at 30 degrees C and 6-8 days, respectively. Regeneration frequency was 0.18% plated onto a medium containing 0.6 M sucrose, and 0.08% plated onto a medium containing mannitol. But hardly any regeneration was observed in the media containing NaCl, KCl, or MgSO(4). More than 90% of the protoplasts contianed nuclei and the nucleus number per protoplast was 1.1. The DNA content per nucleus was 5.1 pg. The diameter of the protoplast was 3-5 mum and it had a well defined cell structure.

Pleurotus mushrooms. Part IB. Pathology, in vitro and in vivo growth requirements, and world status

Part IB of this review discusses growth abnormalities and diseases of the fruit bodies, as well as containments in the substrates that affect the quality and yield of the fruit bodies. The means and methods to overcome these problems during culturing of Pleurotus on commercial scales are described. In vitro growth requirements and prospects of producing mycelium on organic wastes in liquid culture are discussed. The effects of changes in the nutrients of growth substrate on the yield and quality of fruit bodies in vivo are brought out. Status of culturing Pleurotus in different parts of the world is evaluated. Finally, a critical consideration of the scope and problems of Pleurotus cultivation technology is given.

Pleurotus mushrooms. Part I A. Morphology, life cycle, taxonomy, breeding, and cultivation

Pleurotus species represent a well-defined group of Basidiomyceteous fungi of the order Agaricales and family Tricholomataceae. They are characterized by the production of fruit bodies with an eccentric stalk and a wide cap shaped like an oyster shell, with the widest portion of the cap being away from the stalk. They grow over a wide range of temperatures and are able to colonize a wide spectrum of unfermented, natural, lignino-cellulosic wastes. Because of their fast mycelial growth rate, they colonize the substrates rapidly; the yield of fruit bodies is also high. The bifactorial inheritance, observed in many of the species, suggests the likelihood of a high degree of genetic variability, and, hence, considerable breeding potential. Pleurotus species can be grown on a commercial scale, without the need for composting and artificial conditioning of the ambient temperature. Aspects of basic and applied research--such as morphology, life cycle, taxonomy, breeding, and cultivation--leading to development of a "Pleurotus Technology" are dealt with here.

Fruiting Body Formation from Regenerated Mycelium of Pleurotus ostreatus Protoplasts

Fruiting bodies were induced from mycelium regenerated from Pleurotus ostreatus protoplasts. Mycelia originated from protoplasts conformed to parental strain mycelia in morphology. Six strains selected at random from the dikaryotic regenerants were able to form normal fruiting bodies, yielding 18% more than the parent.