RNA-seq Profiling Showed Divergent Carbohydrate-Active Enzymes (CAZymes) Expression Patterns in Lentinula edodes at Brown Film Formation Stage Under Blue Light Induction

Abstract

Lentinula edodes (shiitake mushroom) is one of the most important edible mushrooms worldwide. The L. edodes cultivation cycle includes a unique developing stage called brown film formation that directly affects the development of primordium and the quality of fruiting body. Brown film formation is induced by light, especially blue light. To promote our understanding of the role of blue light in brown film formation mechanisms of L. edodes, we used RNA-seq and compared the transcriptomes of L. edodes grown under blue light and in dark, and validated the expression profiles using qRT-PCR. Blue light stimulated the formation of brown film and increased the content of polysaccharides in L. edodes. Blue light also promoted L. edodes to absorb more polysaccharides by enhancing the activities of enzymes. Among the 730 differentially expressed genes (DEGs), 433 genes were up-regulated and 297 were down-regulated. Most of the DEGs were in the oxidoreductase activity group. Pentose and glucuronic acid conversion and starch and sucrose metabolism were the most important pathways in the formation of brown film. A total of 79 genes of DEGs were identified as genes encoding carbohydrate-active enzymes (CAZymes). Fifty-one of the CAZymes genes were up-regulated, suggesting that CAZymes play important roles in brown film formation to provide sufficient nutrition for L. edodes. The results will facilitate future functional investigations of the genes involved in the developmental control of L. edodes.

Keywords: CAZymes; Lentinula edodes; RNA-seq; blue light; brown film formation.

FIGURE 1

Comparison of L. edodes grown (A) in dark and (B) under blue light, and (C) contents of crude polysaccharides in brown film grown in dark and under blue light.

FIGURE 2

Gene ontology (GO) enrichment in L. edodes grown under blue light as compared to the dark grown control treatment. (A) Biological processes GO term distribution. (B) Molecular functions GO term distribution. (C) Cellular components GO term distribution. The GO items are represented by a node, and edges represent an inclusion relationship. The darker the node, the higher the enrichment.

FIGURE 3

The KEGG pathways with highest number of differentially expressed genes in L. edodes grown under blue light as compared to the dark grown control treatment.

FIGURE 4

(A) The numbers of differentially expressed genes in pentose and glucuronic acid conversion (ko00040) and starch and sucrose metabolism (ko00500) pathways in L. edodes grown under blue light as compared to the dark grown control treatment. (B) The expression of LENED_005053 gene.

FIGURE 5

Number and distribution of (A) up-regulated and (B) downregulated CAZymes genes in L. edodes grown under blue light as compared to the dark grown control treatment. AAs, auxiliary activities; CBMs, carbohydrate-binding modules; CEs, carbohydrate esterases; GHs, glycosyl hydrolases; GTs, glycosyl transferases; PLs, polysaccharide lyases.

FIGURE 6

The expression levels of CAZymes CBM54 (LENED_005589), CE10 (LENED_007609), GH13 (LENED_004582), GH25 (LENED_001073), GT1 (LENED_007286), PL10 (LENED_012509) and PL7 (LENED_004566) in L. edodes grown under blue light as compared to the dark grown control treatment as determined by qRT-PCR.

FIGURE 7

Comparison of MnP, laccase, pectin lyase, β-glucosidase, exo-1,4-beta-glucanase and endo-1,4-beta-glucanase activities at brown film formation stage in L. edodes grown under blue light and dark grown control treatment.