Pacbio Full Length Transcript Sequencing And Illumina Transcriptome Insight Into Immune Defense Mechanism Of Litopenaeus Vannamei Under Ammonia-N Stress

To investigate the immune defense mechanism of Litopenaeus vannamei (L. vannamei) exposed to high concentration of environmental ammonia-N, PacBio full-length transcriptome and Illumina transcriptome sequencing were performed. After ammonia-N exposure, 24,763 and 32,132 full-length transcripts were obtained, while 4465 and 3022 new genes were annotated at 0 and 6 h after compared to L. vannamei whole genome, respectively. Besides, haemocytes transcriptomes, performed at 0, 6 and 48 h, obtained a total of 1017 differentially expressed genes (DEGs), and among them 160 DEGs related to neuroendocrine-immune (NEI) were screened, of which 40 DEGs have alternative splicing form. The following experiments showed that plasma 5-HT and ACh concentrations increased significantly, and then returned to the initial level at 48 h. Moreover, cell membrane receptors (5-HT7R, ACh7R and Toll3), G-protein effectors (AC2 and PLC) and CaM all significantly upregulated, and nuclear transcription factor NF-KB was significantly downregulated, suggesting that 5-HT can act on AC-PKA, PLC -PKC and PLC -CaM pathways through 5-HT7R, and subsequently function on NF-KB together with ACh through ACh7R pathway to affects downstream effector proteins expression. Toll3 pathway is also activated to participate in signal transduction process simultaneously. Furthermore, the expressions of BGBP, PPO3, C-lectin, ALF, LYC and AIF3 were significantly increased, while Syntaxin and Cubilin were significantly decreased. The corresponding immune defense parameters including the THC, PO activity, haemocytes phagocytosis rate, antibacterial and bacteriolytic activities were significantly decreased. All results indicate that after ammonia-N stress, 5-HT, ACh and Toll3 can transfer signal into haemocytes to affect effector proteins and finally reduce immune defense parameters of L. vannamei. This study contributes to better exploration the immune defense mechanism of crustaceans under ammonia-N stress.