Screening and Identification of the Host Proteins Interacting with Toxoplasma gondii Rhoptry Protein ROP16

The Immunoprotective Effect of ROP27 Protein of Eimeria tenella

Eimeria tenella rhoptry protein has the properties of a protective antigen. EtROP27 is a pathogenic gene that is detected via a transcriptome, but its expression pattern, immunogenicity, and potency are unknown. Therefore, a gene segment of EtROP27 was amplified and transplanted into the pET28a prokaryotic vector for the expression of the recombinant protein, and it subsequently purified for the generation of a polyclonal antibody. Then, RT-PCR and Western blotting were performed to understand the expression pattern of EtROP27. Subsequently, animal experiments were conducted to evaluate the immunoprotective effect of the recombinant protein with different immunizing doses (50, 100, and 150 μg). The results showed that the expression of EtROP27 gradually increased with the prolongation of infection time, reaching the highest level at 96 h and then decreasing. Additionally, EtROP27 is a natural antigen of coccidia that can stimulate the body to produce high levels of IgY. As with recombinant protein vaccines, the results of immune protection evaluation tests showed that the average weight gain rates of the immune challenge groups were significantly higher than that of the challenged control group, and their average lesion scores were significantly lower than that of the challenged control group. Furthermore, the oocyst excretion decreased by 81.25%, 86.21%, and 80.01%, and the anticoccidial index was 159.45, 171.47, and 166.75, respectively, for these groups. EtROP27 is a promising antigen gene candidate for the development of a coccidiosis vaccine.

ROP16 of Toxoplasma gondii Inhibits Innate Immunity by Triggering cGAS-STING Pathway Inactivity through the Polyubiquitination of STING

cGAS-STING signaling is a major pathway in inducing type Ⅰ IFN, which plays a crucial role in the defense against T. gondii infection. In contrast, T. gondii develops multiple strategies to counteract the host defense, causing serious diseases in a wide range of hosts. Here, we demonstrate that T. gondii rhoptry protein 16 (ROP16) dampens type I interferon signaling via the inhibition of the cGAS (cyclic GMP-AMP synthase) pathway through the polyubiquitination of STING. Mechanistically, ROP16 interacts with STING through the SignalP domain and inhibits the K63-linked ubiquitination of STING in an NLS (nuclear localization signal)-domain-dependent manner. Consequently, knocking out the ROP16 in PRU tachyzoites promotes the STING-mediated production of type I IFNs and limits the replication of T. gondii. Together, these findings describe a distinct pathway where T. gondii exploits the ubiquitination of STING to evade host anti-parasite immunity, revealing new insights into the interaction between the host and parasites.

Genome-Wide Identification of the TIFY Family in Salvia miltiorrhiza Reveals That SmJAZ3 Interacts With SmWD40-170, a Relevant Protein That Modulates Secondary Metabolism and Development

Salvia miltiorrhiza Bunge (S. miltiorrhiza), a traditional Chinese medicinal herb, contains numerous bioactive components with broad range of pharmacological properties. By increasing the levels of endogenous jasmonate (JA) in plants or treating them with methyl jasmonate (MeJA), the level of tanshinones and salvianolic acids can be greatly enhanced. The jasmonate ZIM (JAZ) proteins belong to the TIFY family, and act as repressors, releasing targeted transcriptional factors in the JA signaling pathway. Herein, we identified and characterized 15 TIFY proteins present in S. miltiorrhiza. Quantitative reverse transcription PCR analysis indicated that the JAZ genes were all constitutively expressed in different tissues and were induced by MeJA treatments. SmJAZ3, which negatively regulates the tanshinones biosynthesis pathway in S. miltiorrhiza and the detailed molecular mechanism is poorly understood. SmJAZ3 acts as a bait protein to capture and identify a WD-repeat containing the protein SmWD40-170. Further molecular and genetic analysis revealed that SmWD40-170 is a positive regulator, promoting the accumulation of secondary metabolites in S. miltiorrhiza. Our study systematically analyzed the TIFY family and speculated a module of the JAZ-WD40 complex provides new insights into the mechanisms regulating the biosynthesis of secondary metabolites in S. miltiorrhiza.

Loss of rhoptry protein 9 impeded Toxoplasma gondii infectivity

Toxoplasma gondii is an obligatory intracellular parasite that critically depends on active invasion and egress from infected host cells to complete its propagation cycle. T. gondii rhoptry proteins (TgROPs) are virulent factors associated with host cell invasion, growth. In this study, we analyzed the functions of ROP9 in the process of T. gondii infection. The TgROP9 knockout RH strain (RH△ROP9) and its recovery strain (RH-ReROP9) were constructed using the CRISPR/Cas9 system. The invasion, proliferation, and egress efficiency of the RH△ROP9 strain were evaluated and their pathogenicity to mice was analyzed. Compared with RH wild-type (RH-WT) and RH-ReROP9 strains, the invasion percentage of RH△ROP9 to Vero cells was reduced by about 28.0% (p< 0.01) at 1.5 h, and the relative proliferation percentage was decreased by about 35.0% (p< 0.01) after infection with 10² or 10³ parasites. In addition, the RH△ROP9 strain also showed prolonged egress time from host cells. The survival time of the mice (12.6 ± 1.6 or 10.1 ± 1.1 days) were delayed (p < 0.001) after infection with either 200 or 1000 RH△ROP9 parasites. These evidences suggested that ROP9 facilitated T. gondii infection in vitro and in vivo.

Life cycle stages, specific organelles and invasion mechanisms of Eimeria species

Apicomplexans, including species of Eimeria, pose a real threat to the health and wellbeing of animals and humans. Eimeria parasites do not infect humans but cause an important economic impact on livestock, in particular on the poultry industry. Despite its high prevalence and financial costs, little is known about the cell biology of these 'cosmopolitan' parasites found all over the world. In this review, we discuss different aspects of the life cycle and stages of Eimeria species, focusing on cellular structures and organelles typical of the coccidian family as well as genus-specific features, complementing some 'unknowns' with what is described in the closely related coccidian Toxoplasma gondii.

Comparison of splenocyte microRNA expression profiles of pigs during acute and chronic toxoplasmosis

BACKGROUND

Toxoplasma gondii is an obligate intracellular parasite that infects humans and other warm-blooded animals. Previous quantitative proteomic analyses of infected host cells revealed that the expression of many host proteins is modulated by T. gondii infection. However, at present limited data are available on the differentially expressed miRNAs (DEMs) associated with the pathology and host immune responses induced by acute and chronic infection with T. gondii in pigs in vivo. In this study, high-throughput sequencing was used to investigate expression profiles of spleen miRNAs at 10, 25 and 50 days post-infection (DPI) in pigs infected with Chinese I genotype strain T. gondii isolated from a dead pig.

RESULTS

When compared to the control group, 34, 6 and 86 DEMs were found in spleens of infected pigs at 10, 25 and 50 DPI, respectively. Gene Ontology (GO) enrichment analysis of the target genes of DEMs showed that no GO terms were enriched at 25 DPI, whereas 28 and 241 GO terms, of which two and 215 were sample-specific, were significantly enriched at 10 and 50 DPI, respectively. The top 20 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways of the target genes of DEMs included signal transduction, immune system, metabolism and diseases. miRNA-gene network analysis revealed that the DEMs played important roles in the host immune response to T. gondii infection by modulating expression levels of cellular immunity-related cytokines and immune-related C-type lectins.

CONCLUSION

Our results not only showed that host miRNA expression is altered by T. gondii but also revealed differences in the regulation of key biological processes and pathways involved in host responses to acute versus chronic T. gondii infection. This will aid future research into miRNA-target interactions during T. gondii infection in pigs and the development of novel therapies against T. gondii.

Toxoplasma gondii Manipulates Expression of Host Long Noncoding RNA during Intracellular Infection

Long noncoding RNA (lncRNA) are non-protein-coding transcripts greater than 200 nucleotides that regulate gene expression. The field of transcriptomics is only beginning to understand the role of lncRNA in host defense. Little is known about the role of lncRNA in the response to infection by intracellular pathogens such as Toxoplasma gondii. Using a microarray, we examined the differential expression of 35,923 lncRNAs and 24,881 mRNAs in mouse bone-marrow-derived macrophages during infection with high- and low-virulence T. gondii strains. We found that 1,522 lncRNA molecules were differentially regulated during infection with the high-virulence Type I strain, versus 528 with the less-virulent Type II strain. Of these lncRNAs, 282 were co-regulated with a nearby or overlapping mRNA–including approximately 60 mRNAs with immune-related functions. We validated the microarray for 4 lncRNAs and 4 mRNAs using qRT-PCR. Using deletion strains of T. gondii, we found that the secretory kinase ROP16 controls upregulation of lncRNAs Csf1-lnc and Socs2-lnc, demonstrating that the parasite directly manipulates host lncRNA expression. Given the number of regulated lncRNAs and the magnitude of the expression changes, we hypothesize that these molecules constitute both an additional regulatory layer in the host response to infection and a target for manipulation by T. gondii.

SmMYB111 Is a Key Factor to Phenolic Acid Biosynthesis and Interacts with Both SmTTG1 and SmbHLH51 in Salvia miltiorrhiza

Transcription factors that include myeloblastosis (MYB), basic helix-loop-helix (bHLH), and tryptophan-aspartic acid (WD)-repeat protein often form a ternary complex to regulate the phenylpropanoid pathway. However, only a few MYB and bHLH members involved in the biosynthesis of salvianolic acid B (Sal B) have been reported, and little is known about Sal B pathway regulation by the WD40 protein transparent testa glabra 1 (TTG1)-dependent transcriptional complexes in Salvia miltiorrhiza. We isolated SmTTG1 from that species for detailed functional characterization. Enhanced or reduced expression of SmTTG1 was achieved by gain- or loss-of-function assays, respectively, revealing that SmTTG1 is necessary for Sal B biosynthesis. Interaction partners of the SmTTG1 protein were screened by yeast two-hybrid (Y2H) assays with the cDNA library of S. miltiorrhiza. A new R2R3-MYB transcription factor, SmMYB111, was found through this screening. Transgenic plants overexpressing or showing reduced expression of SmMYB111 upregulated or deregulated, respectively, the yields of Sal B. Both Y2H and bimolecular fluorescent complementation experiments demonstrated that SmMYB111 interacts with SmTTG1 and SmbHLH51, a positive regulator of the phenolic acid pathway. Our data verified the function of SmTTG1 and SmMYB111 in regulating phenolic acid biosynthesis in S. miltiorrhiza. Furthermore, ours is the first report of the potential ternary transcription complex SmTTG1-SmMYB111-SmbHLH51, which is involved in the production of Sal B in that species.