Transcriptional regulation of laccase and cellulase in relation to fruit body formation in the mycelium of Lentinula edodes on a sawdust-based substrate

Abstract

Extracellular enzyme activities of laccase and cellulase and their transcriptional regulation were investigated at various growth stages in a sawdust-based substrate for Lentinula edodes. Changes of laccase and cellulase activities revealed a clear relationship with fruit body development stages, Laccase and cellulase activities were regulated at the level of gene transcription, The level of laccase mRNA was maximal at the fully colonized stage and declined during fruit body development. Cellulase mRNA began to accumulate at the pin (miniature fruit bodies) formation stage. Cellulase mRNA transcripts were maximally expressed at the veil-break stage of fruit body development. This tendency was clearer in the fruiting cultures with the wide-range-weather strains than in non-fruiting cold-weather strains. Transcription of laccase and cellulase genes was also affected by the water conditions of the sawdust-based substrate. Primordia initiation occurred when the water potential of the medium was high for rapid mRNA transcription by the mycelium.Key Words cxtracellular enzyme; fruit body; Lentinula edodes; mRNA; transcriptional regulation.Lentinula edodes (Berk.) Pegler (shiitake) is the second most important cultivated mushroom in the world. Production in Japan in 1997 was estimated at 250,000 metric tons and valued 171 billion yen (US 1.6 billion). In Japan, indoor cultivation on a hardwood sawdustbased substrates is rapidly replacing traditional cultivation in bed-logs in the open air. The sawdust-based cultivation method for L. edodes has advantages such as a shorter cultivation period and better manipulation of flushing (fruit body formation) by control of environmental conditions. This method now accounts for about a half of all production and is expected to become the major cultivation method.The major nutritional components of the growth medium comprise the various lignocellulose polymers from sawdust cells and some nutritional additives. Several extracellular enzyme activities of L. edodes have been detected in the sawdust-based substrate. These include laccase, peroxidases, cellulases, hemicellulases, proteases, and various glycosidases. Biodegradation is achieved by secretion of a set of extracellular enzymes. Laccase and cellulase especially have been studied in depth since their activities revealed rapid changes during fruit body development in L. edodes (Leatham and Stahmann, 1981; Leatham, 1985;Ohga, 1992) and in Agaricus bisporus (Turner, 1974;Turner et al., 1975; * Corresponding author. E-rnail: ohgasfor(~rnbox.nc.kyushu-u.ac.jp Wood and Goodenough, 1977;Manning and Wood, 1983;Claydon et al. 1988). The growth of the mycelium and the production of fruit bodies are predominantly dependent on the efficient utilization by the extracellular enzymes of the lignocellulose polymers of the sawdustbased substrate. Increase in utilization of substrate is a target for strain manipulation, and this could be achieved by regulation of extracellular enzyme level, using strain selection methods including genetic eng...

Biomass, laccase and endoglucanase production by Lentinula edodes during solid state fermentation of reed grass, bean stalks and wheat straw residues

“…At the end of colonization, just before fruiting, a second cycle of endoglucanase activity was observed. Decrease of laccase activity and a complementary increase in the cellulose activity has been associated with primordium formation (Ohga 1992;Ohga et al 2000). Through this pattern, at the sporophore production phase the polysaccharides are easily available as carbon source to support fructification process.…”

“…Ohga et al (2000), studying laccase and cellulose activity changes of L. edodes during colonization and fruiting stages on sawdust based substrate, demonstrated that secretion of the enzymes is controlled at the level of gene transcription. Cavallazzi et al (2004) demonstrated different behavior of L. edodes strains regarding lignocellulolytic enzymes profiles in SSF of eucalyptus bark-based medium, particularly during the colonization phase.…”

Lignocellulolytic enzyme activity, substrate utilization, and mushroom yield by Pleurotus ostreatus cultivated on substrate containing anaerobic digester solids

“…CMCase activities also decreased after mushroom fruiting in most SCs tested. It is known that high CMCase activities are associated with the fruiting period, and Ohga et al [32] reported that cellulase messenger RNA (mRNA) transcripts were maximally [38] also reported high cellulase productivity in the second month, which occurred during the fruiting phase of the Pleurotus spp. There was no correlation between CMCase activities and fruit-body production.…”

Species richness, abundance, and phenology of fungal fruit bodies over 21 years in a Swiss forest plot

“…Therefore fruit bodies, more than mycelia in general, are important in the context of nature conservation and management. Of course, fruit bodies have specific functional role(s) : (1) in the dissemination of spores for the establishment of new mycelia, or perhaps for the genetic adaptation of existing ones or even for the prevention of gene flow (Fries 1981, Gregory 1984 ; (2) on micro-and macrofauna due to their food value (Avila, Johanson & Bergstrom 1999, North, Trappe & Franklin 1997 ; and (3) maybe on soil mineralisation if developmentally regulated extracellular enzyme systems and differential resource utilisation as in Agaricus bisporus and Lentinula edodes (Turner et al 1975, Wood & Goodenough 1977, Ohga et al 2000 are common.…”