Differential transcriptome analysis of the disease tolerant Madagascar-Malaysia crossbred black tiger shrimp, hepatopancreas in response to acute hepatopancreatic necrosis disease (AHPND) infection: inference on immune gene response and interaction.

BACKGROUND

is the second most widely cultured marine shrimp species in the global shrimp aquaculture industry. However, the growth of production has been constantly impaired by disease outbreaks. Recently, there is a lethal bacterial infection, known as acute hepatopancreatic necrosis disease (AHPND) caused by AHPND strain ( ), which led to mass mortalities in . Unfortunately, there is still insufficient knowledge about the underlying immune response of upon AHPND infection. The present study aims to provide an insight into the antibacterial immune response elicited by hepatopancreas towards AHPND infection.

METHODS

We have employed high-throughput RNA-Seq technology to uncover the transcriptome changes of hepatopancreas when challenged with . The shrimps were challenged with through immersion method with dissected hepatopancreas samples for the control group (APm-CTL) and treatment group at 3 (APm-T3), 6 (APm-T6), and 24 (APm-T24) hours post-AHPND infection sent for RNA-Seq. The transcriptome de novo assembly and Unigene expression determination were conducted using Trinity, Tgicl, Bowtie2, and RSEM software. The differentially expressed transcripts were functionally annotated mainly through COG, GO, and KEGG databases.

RESULTS

The sequencing reads generated were filtered to obtain 312.77 Mb clean reads and assembled into 48662 Unigenes. Based on the DEGs pattern identified, it is inferred that the PAMPs carried by or associated toxins are capable of activating PRRs, which leads to subsequent pathway activation, transcriptional modification, and antibacterial responses (Phagocytosis, AMPs, proPO system). DAMPs are released in response to cell stress or damage to further activate the sequential immune responses. The comprehensive interactions between , chitin, GbpA, mucin, chitinase, and chitin deacetylase were postulated to be involved in bacterial colonization or antibacterial response.

CONCLUSIONS

The outcomes of this research correlate the different stages of immune response to different time points of AHPND infection. This finding supports the development of biomarkers for the detection of early stages of colonization in through host immune expression changes. The potential genes to be utilized as biomarkers include but not limited to C-type lectin, HMGB1, IMD, ALF, serine proteinase, and DSCAM.