Differential STAT gene expressions of Penaeus monodon and Macrobrachium rosenbergii in response to white spot syndrome virus (WSSV) and bacterial infections: Additional insight into genetic variations and transcriptomic highlights

Abstract

Diseases have remained the major issue for shrimp aquaculture industry for decades by which different shrimp species demonstrated alternative disease resistance or tolerance. However, there had been insufficient studies on the underlying host mechanisms of such phenomenon. Hence, in this study, the main objective involves gaining a deeper understanding into the functional importance of shrimp STAT gene from the aspects of expression, sequence, structure, and associated genes. STAT gene was selected primarily because of its vital signalling roles in stress, endocrine, and immune response. The differential gene expressions of Macrobrachium rosenbergii STAT (MrST) and Penaeus monodon STAT (PmST) under White Spot Syndrome Virus (WSSV) and Vibrio parahaemolyticus/VpAHPND infections were identified through qPCR analysis. Notably, during both pathogenic infections, MrST demonstrated significant gene expression down-regulations (during either early or later post-infection time points) whereas PmST showed only significant gene expression up-regulations. Important sequence conservation or divergence was highlighted through STAT sequence comparison especially amino acid alterations at 614 aa [K (Lysine) to E (Glutamic Acid)] and 629 aa [F (Phenylalanine) to V (Valine)] from PmST (AY327491.1) to PmST (disease tolerant strain). There were significant differences observed between in silico characterized structures of MrST and PmST proteins. Important functional differentially expressed genes (DEGs) in the aspects of stress, endocrine, immune, signalling, and structural were uncovered through comparative transcriptomic analysis. The DEGs associated with STAT functioning were identified including inositol 1,4,5-trisphosphate receptor, hsp90, caspase, ATP binding cassette transmembrane transporter, C-type Lectin, HMGB, ALF1, ALF3, superoxide dismutase, glutathione peroxidase, catalase, and TBK1. The main findings of this study are STAT differential gene expression patterns, sequence divergence, structural differences, and associated functional DEGs. These findings can be further utilized for shrimp health or host response diagnostic studies. STAT gene can also be proposed as a suitable candidate for future studies of shrimp innate immune enhancement.

Fig 1. Comparative gene expression fold change of MrST and PmST against time post-infection (hours) (WSSV and V. parahaemolyticus/Vp_AHPND).

All relative gene expression fold changes were statistically significant (P<0.05). The error bars indicated standard deviations of the data. [MrST (WSSV) Fold changes: 0 hpi: -1.113; 3 hpi: -2.332; 6 hpi: -4.699; 12 hpi: -2.038; 24 hpi: 2.287; 48 hpi: 2.017]. [PmST (WSSV) Fold changes: 0 hpi: 1.650; 3 hpi: 1.500; 6 hpi: 1.729; 12 hpi: 7.082; 24 hpi: 10.691; 48 hpi: 2.510]. [MrST (V. parahaemolyticus) Fold changes: 0 hpi: 1.238; 3 hpi: 2.272; 6 hpi: -1.766; 12 hpi: -3.262; 24 hpi: -5.429; 48 hpi: -1.125]. [PmST (Vp_AHPND) Fold changes: 0 hpi: 1.622; 3 hpi: 3.059; 6 hpi: 2.500; 12 hpi: 2.298; 24 hpi: 3.139; 48 hpi: 1.273].

Fig 2. Sequence comparison of MrST, LvST, PmST (New) (disease tolerant strain), and PmST (Accession number: AY327491.1) translated amino acid sequences.

* represents common conserved sites between all sequences. represents important long conserved overlaps between all sequences. represents important divergent sites between PmST (cross-bred disease tolerant strain) and PmST (Accession number: AY327491.1). represents important divergent sites between MrST and other STAT sequences. represents important amino acid addition or deletion between MrST and other STAT sequences.

Fig 3. Overall comparison of important DEGs involving type of DEGs-treatment group and number of DEGs.

Treatment Groups: WM: WSSV-infected M. rosenbergii; VM: V. parahaemolyticus-infected M. rosenbergii; WP: WSSV-infected P. monodon at 12 dpi; AP: Vp_AHPND-infected P. monodon. Stress DEGs: Inositol 1,4,5-trisphosphate receptor, Dopamine N-acetyltransferase, Hsp90, Apoptosis-stimulating of p53 protein 1, Caspase, Apoptosis-inducing factor (AIF). Endocrine DEGs: Mitochondrial coenzyme A transporter, ATP binding cassette transmembrane transporter, Trehalose transporter, Polysaccharide lyase, Trypsin, Peroxisomal acyl-coenzyme A oxidase. Immune DEGs: Transglutaminase, C-type Lectin, HMGB, ALF1, ALF3, proPO, Superoxide Dismutase, Glutathione Peroxidase, Catalase. Signalling DEGs: Ceramide synthase, Calcium-activated chloride channel regulator, Inward rectifier potassium channel, STAT, IMD, TBK1. Structural DEGs: Actin, Ankyrin.