Comparative transcriptomic analysis provides insights into immune responses of lamprey larvae under three pathogens infections

Based on the large number of deaths of lamprey larvae infected by pathogens in the culture process, the infection response of lamprey larvae to different pathogens was studied. Thus, high-throughput sequencing is firstly used to analyze the lamprey larvae infected by Aeromonas hydrophila, Vibrosplendidus, and Saprolegnia parasitica. A high quality of 338,628,426 Reads were obtained and 203,829 transcripts were assembled. A total of 158,001 Unigenes were annotated by Blast comparison, and a relatively comprehensive transcriptome database of lamprey larvae was established. Based on the transcriptome of lamprey larvae infected by three aquatic pathogens, classification results of COG and GO show that the genes classified into signal transduction mechanism accounted for the largest proportion, and 2316 differentially expressed genes were identified and screened out. After infection by the three pathogens, 16 genes and 19 genes expression were up-regulated and down-regulated, respectively. KEGG pathway analysis of differentially expressed genes showed that lamprey larvae were mainly affected their metabolism and oxidative phosphorylation pathways after infection by two gram-negative bacteria, Vibrosplendidus and Aeromonas hydrophila. As a fungus, Saprolegnia parasitica mainly affected ribosome synthesis in lamprey larvae. The results were validated by detecting the expression levels of 13 DEGs at 24 h after pathogens treatment using Q-PCR. The results provide valuable information for further research into the development of immunity and the innate immune response against pathogen invasion during the artificial propagation of lamprey larvae.