Lentinan Degradation in the Lentinula edodes Fruiting Body during Postharvest Preservation Is Reduced by Downregulation of the exo-β-1,3-Glucanase EXG2

Abstract

Lentinan from Lentinula edodes fruiting bodies (shiitake mushrooms) is a valuable β-glucan for medical purposes based on its anticancer activity and immunomodulating activity. However, lentinan content in fruiting bodies decreases after harvesting and storage due to an increase in glucanase activity. In this study, we downregulated the expression of an exo-β-1,3-glucanase, exg2, in L. edodes using RNA interference. In the wild-type strain, β-1,3-glucanase activity in fruiting bodies remarkably increased after harvesting, and 41.7% of the lentinan content was lost after 4 days of preservation. The EXG2 downregulated strain showed significantly lower lentinan degrading activity (60-70% of the wild-type strain) in the fruiting bodies 2-4 days after harvesting. The lentinan content of fresh fruiting bodies was similar in the wild-type and EXG2 downregulated strains, but in the downregulated strain, only 25.4% of the lentinan was lost after 4 days, indicating that downregulation of EXG2 enables keeping the lentinan content high longer.

Lentinula edodes Genome Survey and Postharvest Transcriptome Analysis

“…Lentinula edodes has three GH55 family exo-␤-1,3-glucanases that are mostly conserved in filamentous fungi and also exist in several bacteria (39). EXG2, a member of the GH55 family which is involved in cell wall degradation after harvest (27), has a strong effect on lentinan degradation after harvest (40). The enzyme encoded by exg2 in the GH55 family of exo-␤-1,3-glucanases was not determined to be a DEG, but its expression was upregulated more than 15-fold in the fruiting body after harvest (Table 2).…”

“…2). RNA interference tools are available in Lentinula edodes (40,73), and TILLING, a method for screening mutants that have a mutation in a target gene (74), will be applicable for breeding. Gene expression for wood decay, biofilm formation in sawdust, medium cultivation, and fruiting body primordia in Lentinula edodes has been reported.…”

Intensive pulsed light pretreatment combined with controlled temperature and humidity for convection drying to reduce browning and improve quality of dried shiitake mushrooms

“…31 On the content of dried shiitake Table 1. Effects of intensive pulsed light (IPL) and hot water blanching (HB) pretreatments on shiitake mushroom polysaccharides (SMPs), 5-hydroxymethylfurfural (5-HMF), reducing sugars content (RSC), total phenolic content (TPC), surface color, browning index (BI) and browning degree (BD) of dried shiitake mushrooms 32 However, the range of dried SMPs pretreated with HB decreases by 17.65% compared with the untreated sample. Polysaccharides might engender this decline because of their high solubility in water (after blanching pretreatment) and because of non-enzymatic browning, which started at higher temperatures.…”

Overexpressing Pleurotus ostreatus rho1b results in transcriptional upregulation of the putative cellulolytic enzyme‐encoding genes observed in ccl1 disruptants

“…The Rho1‐Mpk1 cascade is involved in cell wall biosynthesis in various fungi (Kwon et al ., 2010; Lam et al ., 2013); thus, it is possible that some of the GH/AA‐encoding genes upregulated in the ccl1 disruptants and the rho1b OE strains are involved in cell wall biosynthesis, but not in cellulose degradation. Various studies have suggested that cell wall biosynthesis/remodelling may be related to fruiting body development in some agaricomycetes (Kamada et al ., 1991; Muraguchi and Kamada, 2000; Tao et al ., 2013; Konno et al ., 2014; Zhou et al ., 2019); therefore, we analysed the effects of rho1b or mpk1b disruption on fruiting development to examine this possibility.…”