Transcriptome analysis of hepatopancreas of Litopenaeus vannamei after acute exposure to Alexandrium pacificum

Physiological Responses in the Hepatopancreas of Litopenaeus vannamei to Carbonate Alkalinity Stress and Subsequent Recovery: Integration of Antioxidant, Immune, and Metabolic Profiles

High carbonate alkalinity (CA) is a major constraint on shrimp culture in saline–alkaline waters. The hepatopancreas is central to shrimp immunity and metabolic regulation. Litopenaeus vannamei underwent a 7-day exposure period to 5 mmol/L CA, followed by a subsequent 7-day recovery phase after removal of the stressor. The physiological regulatory mechanism of the hepatopancreas during CA stress and recovery was investigated by integrating multiple biological levels including histomorphology, antioxidant and immune indices, energy metabolism, and metabolite profiles. Results showed that CA stress induced structural changes in the hepatopancreas and triggered stress responses. Specifically, a significant upregulation was observed in genes involved in antioxidation (romo1, nrf2, gpx, hsp70), apoptosis (casp-9, casp-3), endoplasmic reticulum (ER) stress (ire1, xbp1), immune defense (alf, crus, pen-3, lys, propo), and detoxification (cyp450). CA stress also increased osmoregulatory genes (ccp, nhe, ca, aqp, vatp, nka-β, nka-α), whereas clc and tip4 were suppressed. CA stress reduced the levels of energy-metabolism-related biochemical indicators, including glucose (GLU), pyruvic acid (PYR), lactic acid (LAC) and triglycerides (TG), while markedly inducing the expression of genes involved in carbohydrate metabolism (ldh, pdh, hk, pk), lipid metabolism (ampk, srebp, fas), the tricarboxylic acid (TCA) cycle (mdh, cs, idh, odh, sdh, fh), and the electron transport chain (ETC) (ndh, cytc, coi, cco, atph). Moreover, the hepatopancreatic metabolic profile was remodeled, especially “phenylalanine, tyrosine and tryptophan biosynthesis” and the metabolism of β-alanine, arachidonic acid, linoleic acid, and sphingolipids being substantially altered during both the stress and recovery phases. Several functional metabolites linked to stress responses were further pinpointed. Following stress relief, some physiological parameters partially recovered, yet overall function failed to return to normal. Collectively, CA stress compromised hepatopancreatic homeostasis by damaging morphological integrity, eliciting stress and immune responses, and perturbing energy metabolism and metabolite homeostasis; these adverse effects were not readily reversible in the short term.

Dynamic Mechanism of Hepatopancreatic Transcriptomic Response in Litopenaeus Vannamei under PirAB Toxin Challenge: A Time-Series Reanalysis Based on Public Databases

Acute Hepatopancreatic Necrosis Disease (AHPND) poses a major threat to the shrimp aquaculture industry, and its pathogenic agent is the PirAB toxin. Although it is known to target the hepatopancreas, the early events triggered by toxin attack and their dynamic mechanisms along disease progression remain to be elucidated. In this study, time-series transcriptomic data from public databases (control group and 0.5, 1, 2, 4, 6 hours after toxin treatment) were used to reveal a "double-hit" model of PirAB toxin pathogenesis through K-means clustering and key gene expression analysis. The first hit (0.5 h) was characterized by a sharp downregulation of transcription regulatory factors such as zinc finger proteins, leading to paralyzed transcriptional regulation. The second hit (6 h) manifested as sustained inhibition of metabolic genes and upregulation of apoptosis/degradation genes including matrix metalloproteinases, resulting in functional failure and tissue ulceration. This model identified molecular abnormalities at the very early stage, suggesting that zinc finger proteins, metallothioneins and other molecules can serve as biomarkers for ultra-early warning, providing new insights into the early diagnosis of AHPND.

Transcriptomic analysis provides molecular insights into the innate immune defense of Mactra veneriformis against Vibrio alginolyticus infection.

Mactra veneriformis is an economically important bivalve mollusc in China, but its aquaculture is frequently threatened by Vibrio infections, particularly Vibrio alginolyticus. To investigate the molecular immune response of M. veneriformis to V. alginolyticus, we performed RNA-seq analysis of hepatopancreatic tissues collected at 48 h post-infection, the peak mortality time point, with PBS-injected individuals used as controls. Infection with V. alginolyticus caused severe histopathological damage in the hepatopancreas and resulted in a cumulative mortality of 53.3% over 14 d, compared with 3.3% in the control group. Transcriptomic analysis identified 2623 differentially expressed genes (DEGs), including 1585 significantly up-regulated genes and 1038 down-regulated genes. KEGG enrichment analysis demonstrated that DEGs were significantly enriched in immune related and metabolism pathways, including the JAK-STAT signaling pathway, RIG-I-like receptor (RLR) signaling pathway, and cytochrome P450 (CYP450) signaling pathway. Collectively, these findings revealed candidate immune related genes (tlr3, tlr5, myd88, nfkb1, il-17d, and ifi44l), a putative TLR-MyD88-NF-κB signaling axis, and KEGG signaling pathways, including JAK-STAT, RLR and CYP450, that may be involved in the innate immune response of M. veneriformis to V. alginolyticus infection. These results provide a transcriptomic basis for understanding host-pathogen interactions in this species and highlight candidate genes and pathways for future functional validation and potential application in disease-resistance breeding.

Dose-dependent supplementation of Schizochytrium in the biofloc system modulates dual microbiomes to enhance growth and survival in Pacific white shrimp (Litopenaeus vannamei)

Integrating microalgae into biofloc system is a promising yet debated strategy in Pacific white shrimp (Litopenaeus vannamei) aquaculture, due to its inconsistent efficacy even for the same microalgal species. Such inconsistent performances are likely dose-dependent and the underlying microbial mechanisms remain elusive. Here, we investigated the impacts of supplementing microalga strain, Schizochytrium sp. ATCC 20888, at low (103 cells/mL, M1) and high (106 cells/mL, M2) levels compared with a clear water (CLW) system. Schizochytrium supplementation improved growth performance and feed efficiency and the M2 treatment further increased shrimp survival. Transcriptional profiling revealed the M2 treatment upregulated the expression of genes relevant to hepatopancreatic lipid and protein digestion (trypsin and lipase) and intestinal amino acid transportation (peptide transporter 1). Concurrently, M2 fortified the intestinal defense against pathogenic microbes by enhancing antimicrobial genes (lysozyme and penaeidin 3a). Redundancy analysis further supported the growth promotion was closely associated with improved lipid and a corresponding protein-sparing effect. Notably, Schizochytrium persisted at an extremely low abundance, whilst 16S rRNA sequencing revealed its disproportionate impact as a rare taxon on the microbiota in both biofloc and gut. High-dose supplementation enriched beneficial genera such as Aureispira, Marivita, Neptuniibacter, and Phaeodactylibacter in bioflocs, which are vital for nutrient recycling. Meanwhile, the intestinal microbiota was characterized by enrichment of the probiotic Fusibacter and the suppression of the opportunistic pathogen Shewanella. Overall, Schizochytrium orchestrates a dose-dependent reshaping of biofloc and gut microbiomes, effectively boosting the growth, feed efficiency, and specifically reinforcing antimicrobial activity of L. vannamei.

Molecular response of Tribolium castaneum to benzothiazole: insights from transcriptome and functional validation of UGT2B9.

Findings provide insights into the potential multifaceted insecticidal action of benzothiazole in T. castaneum at the transcriptomic level and support its further development as a target-specific grain fumigant.

Stress induction in Hippolyte inermis Leach (1816) larvae by microplastics from manufactured polylactic acid and polypropylene cups