First-principle calculations of the structural, vibrational, mechanical, electronic, and optical properties of ε-O8 under pressure.

The vibrational, mechanical, electronic, and optical properties of the ε-O8 phase in the pressure range of 11.4-70 GPa were studied by the first-principle calculation method. The phonon dispersion curves have a tiny virtual frequency at 60 GPa, which indicates that ε-O8 is dynamically unstable at 60 GPa. However, the 3-BM EOS demonstrates that the unit cell is stable up to 70 GPa. It has been shown that ε-O8 remains ductile within the whole applied pressure range. Concurrently, we calculated the variation of the band gap of ε-O8 in the pressure range of 11.4-70 GPa. The results show that the band gap of ε-O8 decreases with increasing pressure. Notably, the band gap disappears within the range of 50-60 GPa, which reveals that the metallic phase transition occurs within this pressure range.

KLF13 induces apoptotic cell clearance in Penaeus vannamei as an essential part of shrimp innate immune response to pathogens.

Although, in mammals, the Krüppel-like transcription factor 13 (KLF13) plays an essential role in cell proliferation, survival, differentiation, apoptosis, tumorigenesis, immune regulation, and inflammation, its role in penaeid shrimp is unclear. In the current study, we characterized a KLF13 homolog in Penaeus vannamei (PvKLF13), with full-length cDNA of 1677 bp and 1068 bp open reading frame (ORF) encoding a putative protein of 355 amino acids, which contains three ZnF_C2H2 domains. Sequence and phylogenetic analysis revealed that PvKLF13 shares a close evolutionary relationship with KLF13 from invertebrates. Transcript levels of PvKLF13 were ubiquitously expressed in shrimp and induced in hemocytes upon challenge with Vibrio parahaemolyticus, Streptococcus iniae, and white spot syndrome virus (WSSV), suggesting the involvement of PvKLF13 in shrimp immune response to pathogens. Besides, knockdown of PvKLF13 decreased hemocytes apoptosis in terms of increased expression of pro-survival PvBcl-2, but decreased expression of pro-apoptotic PvBax and PvCytochrome C, coupled with high PvCaspase3/7 activity, especially upon V. parahaemolyticus challenge. The findings here indicate the involvement of PvKLF13 in apoptotic cell clearance as an essential part of shrimp innate immune response to pathogens.

The Microbial Composition of Penaeid Shrimps' Hepatopancreas Is Modulated by Hemocyanin.

Aquatic organisms have to produce proteins or factors that help maintain a stable relationship with microbiota and prevent colonization by pathogenic microorganisms. In crustaceans and other aquatic invertebrates, relatively few of these host factors have been characterized. In this study, we show that the respiratory glycoprotein hemocyanin is a crucial host factor that modulates microbial composition and diversity in the hepatopancreas of penaeid shrimp. Diseased penaeid shrimp (Penaeus vannamei), had an empty gastrointestinal tract with atrophied hepatopancreas, expressed low hemocyanin, and high total bacterial abundance, with Vibrio as the dominant bacteria. Similarly, shrimp depleted of hemocyanin had mitochondrial depolarization, increased reactive oxygen species (ROS) levels, and dysregulation of several energy metabolism-related genes. Hemocyanin silencing together with ROS scavenger (N-acetylcysteine) treatment improved microbial diversity and decreased Vibrio dominance in the hepatopancreas. However, fecal microbiota transplantation after hemocyanin knockdown could not restore the microbial composition in the hepatopancreas. Collectively, our data provide, to our knowledge, new insight into the pivotal role of hemocyanin in modulating microbial composition in penaeid shrimp hepatopancreas via its effect on mitochondrial integrity, energy metabolism, and ROS production.

microRNA-589-5p modulates the expression of hemocyanin as part of the anti-WSSV immune response in Litopenaeus vannamei.

The respiratory glycoprotein, hemocyanin (HMC) has multiple immune-related functions, including antiviral activity. In this study, in silico methods were used to predict seven miRNAs targeting Litopenaeus vannamei HMC (LvHMC), out of which miR-589-5p was selected for further investigation because of its role in immune response. Transcript levels of miR-589-5p were ubiquitously distributed in all shrimp tissues examined, and significantly induced in hemocytes and hepatopancreas upon challenge with white-spot syndrome virus (WSSV) as well as by marine bacterial pathogens, which suggest that miR-589-5p is involved in shrimp immune response to pathogens. Morever, using Drosophila S2 cells stably overexpressing EGFP-LvHMC, flow cytometry and dual luciferase reporter assays, miR-589-5p was shown to significantly inhibit the in vitro expression of LvHMC. In addition, in vivo knockdown of miR-589-5p using antagomir-589-5p resulted in significant down-regulation in LvHMC expression, while overexpression of miR-589-5p using agomir-589-5p decreased the level of LvHMC expression in shrimp hemocytes and hepatopancreas. Further, the increased expression of miR-589-5p resulted in high shrimp mortality following WSSV challenge, coupled with an increase in the number of WSSV copies in hemocytes and hepatopancreas. These results suggest that miR-589-5p is involved in shrimp immune response to WSSV by negatively regulating the expression of LvHMC.

The interaction of TAK1 and TAB1 enhances LPS-induced cytokine release via modulating NF-κB activation (Larimichthys crocea).

Transforming growth factor-ß-activating kinase 1 (TAK1) is triggered by foreign pathogenic infection and involves in proinflammatory response through the activation of nuclear factor-κB (NF-κB), which is specifically regulated by TAK1-binding protein 1 (TAB1). However, the expression and regulatory characterizations of TAK1 and TAB1 in fish immune response remain largely unknown. In the present study, the cDNA sequences of TAK1 (LcTAK1) and TAB1 (LcTAB1) were identified from large yellow croaker, Larimichthys crocea. The open reading frame (ORF) of LcTAK1 was 1725 bp in length, encoding 574 amino acids. The putative LcTAK1 protein contained a protein kinase domain and a C-terminal coiled-coil region. The ORF of LcTAB1 was 1518 bp encoding 505 amino acids. And a typical PP2Cc domain and a conserved sequence motif (PYVDFSQFYLLWGSDH) at C-terminal were identified in the predicted LcTAB1 protein. Multiple alignments showed that LcTAK1 shared 74.0-97.9% and LcTAB1 shared 37.4-95.8% sequence identities with TAK1 and TAB1 proteins from other species, respectively. Quantitative PCR analysis indicated that both LcTAK1 and LcTAB1 were broadly expressed in all examined tissues, with the most predominant expression in brain and the weakest expression in muscle, respectively. Subcellular localization revealed that both LcTAK1 and LcTAB1 expressed in the cytoplasm. In addition, LcTAK1 transcripts increased significantly in LCK cells after flagellin, LPS and poly I:C stimulation while LcTAB1 enhanced greatly after LPS and poly I:C challenge. Furthermore, the roles of them in NF-κB activation were investigated by overexpression of LcTAK1 and LcTAB1 in HEK293T cells. Our results revealed that NF-κB luciferase promoter expression could not be induced by overexpression of LcTAK1 or LcTAB1 alone, however, it could be induced by co-expression of LcTAK1 and LcTAB1 together. Moreover, the roles of LcTAK1 and LcTAB1 in immune response analysis showed that NF-κB activation enhanced significantly in co-overexpressed HEK293T cells following LPS and poly I:C stimulation. However, the expression levels of tumor necrosis factor (TNF)-α, Interleukin-6 (IL-6) and IL-8 were induced only after LPS challenge (p < .05). These findings suggested that the TAK1-TAB1 complex of large yellow croaker might play an important role in pro-inflammatory cytokines and chemokine release after LPS stimulation via inducing NF-κB activation.