T lymphocyte was used as research material and RNA-Seq technology was applied for transcription sequencing of T lymphocyte treated with Lactarius deliciosus Gray polysaccharide (LDG-A), lipopolysaccharide (LPS) and blank control. Bioinformatics analysis was carried out to explore the difference of gene expression in T lymphocyte proliferation affected by LDG-A, as well as the main genes and key pathways involved in this process. RNA-Seq results showed that a total of 7.54 G, 7.96 G and 8.62 G analysis data (clean reads) were obtained from the blank control group, LDG-A group and LPS group, respectively. The gene expression levels indicated that 8 genes in LDG-A group, 5 genes in LPS group and 8 genes in blank control group were highly expressed (FPKM>2 200). Analysis of the differentially expressed genes revealed that there were 334 differentially expressed genes between LDG-A group and control group, of which 331 genes were up-regulated and 3 genes were down-regulated. KEGG pathway enrichment results demonstrated that the key genes related to LDG-A affecting T lymphocyte proliferation were mainly concentrated in metabolic pathway, such as MAPK signaling pathway and Ras signaling pathway. Furthermore, Ras-ERK-MAPK signaling pathway played an important role in the process of T lymphocyte proliferation stimulated by LDG-A. The up-regulated expression of fibroblast growth factor-1 (Fgf1), fibroblast growth factor receptor-1(Fgfr1), platelet-derived growth factor subunit A (Pdgfa) and ETS transcription factor ELK1(Elk-1) in this pathway suggested that LDG-A can promote gene expression and proliferation of T lymphocyte through Ras-ERK-MAPK signaling pathway.

Lactarius deliciosus Gray polysaccharide（LDG-A）; T lymphocyte; RNA-Seq; differentially expressed genes; Ras-ERK-MAPK signaling pathway