Transcriptome Analysis of Ganoderma lingzhi Liquid Fermentation Process Using Corn Straw as Matrix

Abstract

Ganoderma lingzhi, a species of white rot fungus, possesses the highest abundance of lignocellulose-degrading enzymes among these fungi, as well as a relatively high carbon conversion rate. Corn straw, as an important sustainable resource, is used as a substrate for the liquid culture of G. lingzhi. However, little is known about the genes encoding the lignocellulose degradation and polysaccharide and triterpenoid biosynthetic pathways involved in this process. This paper employs transcriptomics to uncover the key genes involved in lignocellulose degradation and the synthesis of polysaccharides and triterpenoids during the liquid fermentation of G. lingzhi using corn straw as the substrate, as well as their associations. Carbohydrate-Active enzymes analysis of differential genes in the sequencing results was used to analyze the genes related to lignocellulose degradation. Among these, 43 core genes encoding CAZymes were obtained after 0 to 5 days of fermentation, and 25 core genes encoding CAZymes were obtained after 5 to 12 days of fermentation. The differential expression levels of DN3690_c0_g1 (EGL), DN3627_c0_g2 (XYN), DN4778_c0_g1 (XYN), DN2037_c0_g1 (LACC), and DN277_c2_g1 (MnP) were used to identify the key genes. The polysaccharide synthesis metabolic pathway favored mannitol synthesis, and the expression of triterpene precursor-metabolizing enzyme genes revealed higher expression levels of key enzyme genes such as ACAT, HMGS, and MPK. A correlation clustering analysis of genes related to lignocellulose degradation, polysaccharide, and triterpene anabolism during liquid fermentation showed that lignocellulose degradation genes mainly influenced arabinose and mannitol anabolism, as well as the synthesis of triterpene precursors.