Transcriptomic analysis of Stropharia rugosoannulata reveals carbohydrate metabolism and cold resistance mechanisms under low-temperature stress

Abstract

Low temperature is an important environmental factor that restricts the growth of Stropharia rugosoannulata; however, the molecular mechanisms underlying S. rugosoannulata responses to low-temperature stress are largely unknown. In this study, we performed a transcriptome analysis of a high-sensitivity strain (DQ-1) and low-sensitivity strain (DQ-3) under low-temperature stress. The liquid hyphae of S. rugosoannulata treated at 25 °C and 10 °C were analyzed by RNA-Seq, and a total of 9499 differentially expressed genes (DEGs) were identified. GO and KEGG enrichment analyses showed that these genes were enriched in "xenobiotic biodegradation and metabolism", "carbohydrate metabolism", "lipid metabolism" and "oxidoreductase activity". Further research found that carbohydrate enzyme (AA, GH, CE, and GT) genes were downregulated more significantly in DQ-1 than DQ-3 and several cellulase activities were also reduced to a greater extent. Moreover, the CAT1, CAT2, GR, and POD genes and more heat shock protein genes (HSP20, HSP78 and sHSP) were upregulated in the two strains after low-temperature stress, and the GPX gene and more heat shock protein genes were upregulated in DQ-3. In addition, the enzyme activity and qRT-PCR results showed trends similar to those of the RNA-Seq results. This result indicates that low-temperature stress reduces the expression of different AA, GH, CE, and GT enzyme genes and reduces the secretion of cellulase, thereby reducing the carbohydrate metabolism process and mycelial growth of S. rugosoannulata. Moreover, the expression levels of different types of antioxidant enzymes and heat shock proteins are also crucial for S. rugosoannulata to resist low-temperature stress. In short, this study will provide a basis for further research on important signaling pathways, gene functions and variety breeding of S. rugosoannulata related to low-temperature stress.

Keywords: Antioxidant enzyme; Carbohydrate enzymes; Heat shock protein; Low-temperature stress; Stropharia rugosoannulata; Transcriptomic.

Fig. 1

Physiological performance of the S. rugosoannulata DQ-1 and DQ-3 strains under the different temperature treatments. A and B Mycelial growth state and growth rate of the DQ-1 and DQ-3 strains after treatment at 25 °C and 10 °C. C Mycelial biomass of strains DQ-1 and DQ-3 after treatment at 25 °C and 10 °C. The error bars represent the means ± standard deviations of triplicate experiments

Fig. 2

Statistic of different expressed genes. A Number of differentially expressed genes (DEGs) after the temperature treatments. B Venn diagram of DEGs among the different comparisons. C Heat map showing the expression level of DEGs

Fig. 3

GO functional classification of differentially expressed genes. A–C and D GO enrichment between different treatments. The green bars represent biological processes; yellow bars represent cellular components; and blue bars represent molecular functions. Only the significant GO terms (P < 0.005) were shown

Fig. 4

Difference analysis of carbohydrate enzyme genes under the different temperature treatments. A–D Comparison of the number of differentially expressed carbohydrate enzyme genes between different treatments. E–H Expression levels of the top ten genes with significant changes in each carbohydrate enzyme (AA, GH, CE, GT, CBM and PL) family under the different treatments

Fig. 5

Analysis of carbohydrate enzyme activity and gene expression level verification under the different temperature treatments. A–D Changes in cellulase, exo/endo-β-1,4-glucanase and β-glucosidase activity under the different treatments. E, F Validation of the expression levels of nine differentially expressed CAZymes (AA2, AA5, GH3, GH5, GH9, CE4, GT2, CBM50 and PL14). The error bars represent the means ± standard deviations of triplicate experiments

Fig. 6

Analysis of antioxidant enzyme activity and gene expression levels under the different temperature treatments. A Transcriptome comparative analysis of the expression of antioxidant enzyme genes between different treatments. B and C Changes in SOD and CAT enzyme activities in the DQ-1 and DQ-3 strains under the different temperature treatments. D and Validation of the expression levels of eight differentially expressed antioxidant enzymes (SOD1, SOD2, SOD3, GPX, CAT1, CAT2, GR and POD). The error bars represent the means ± standard deviations of triplicate experiments

Fig. 7

Analysis of heat shock protein expression under the different temperature treatments. A and B Transcriptome comparative analysis of the expression of heat shock protein genes between different treatments. C and D Validation of the expression levels of five differentially expressed heat shock proteins (HSP, sHSP1, sHSP2, sHSP3 and HSP78). The error bars represent the means ± standard deviations of triplicate experiments