Transcriptome analysis of the immunomodulation by Arctium lappa L. polysaccharides in the Chinese mitten crab Eriocheir sinensis against Aeromonas hydrophila

Arctium lappa L. polysaccharide (designated ALP) has been used as an immunomodulator in animals. Immuno-modulation by ALP in the Chinese mitten crab Eriocheir sinensis was detected after Aeromonas hydrophila treatment (1.0 x 10(7) colony-forming units) in this study. ALP significantly inhibited the decrease in the total hemocyte count (THC) (P < 0.05). Twenty transcriptome libraries were constructed from the hemocytes of crabs, and in total, 600,827,724 reads and 794,113 transcripts were obtained and clustered into 337,358 unigenes, which were annotated in the CDD, KOG, NR, NT, PFAM, TrEMBL, GO and KEGG databases. The differentially expressed gene (DEG) analysis indicated that 97,800 genes were upregulated and 103,745 genes were downregulated, among which 2616 and 932 immune-related DEGs were enriched according to the GO and KEGG annotations at 12 h, respectively (Q value<0.05). EsDorsal, EsPI3K, EsLectin and EsLGBP mRNA were upregulated, and STAT mRNA was downregulated significantly after A. hydrophila injection. ALP treatment inhibited the increase in EsDorsal and EsPI3K expression and promoted the increase in EsLectin and EsLGBP expression. The alkaline phosphatase (AP) and glutamyl transpeptidase (GT) activities in the supernatant of the hemolymph increased significantly after ALP treatment, and the immunofluorescence assay indicated that ALP could inhibit the upregulation of TNF-alpha and IL-6 in hemocytes of E. sinensis challenged by A. hydrophila at 12 h. Therefore, it was concluded that ALP played an important role in effective immunomodulation in Chinese mitten crabs (E. sinensis) during A. hydrophila infection.