40S ribosomal protein S18 is a novel maternal peptidoglycan-binding protein that protects embryos of zebrafish from bacterial infections

Comparative transcriptomic analysis reveals a differential acid response mechanism between estuarine oyster (Crassostrea ariakensis) and Pacific oyster (Crassostrea gigas)

Ocean and coastal acidification (OCA) poses a significant and rapidly emerging threat to mollusks. The physiological resilience of mollusks to OCA varies considerably; however, the underlying molecular mechanisms remain poorly understood. Seawater in estuaries, being more susceptible to acidification than that in open coastal zones, may enhance the tolerance of resident mollusks to low pH levels. Here, we conducted a comparative analysis between estuarine oysters (Crassostrea ariakensis) and Pacific oysters (Crassostrea gigas) using physiological phenotype and transcriptomic analyses to reveal differential acid-tolerance mechanisms in response to constant pH of 7.8. Our findings indicated that survival and respiration rates of C. ariakensis, which inhabits estuaries with fluctuating pH levels, were higher than those of C. gigas, which inhabits open coastal zones with relative stable pH conditions. Acid-responsive genes identified in C. gigas, including molecular chaperones and immune-related genes, exhibited higher constitutive expression in C. ariakensis under control conditions. Co-expression analyses revealed that C. ariakensis mitigated the effects of low pH by expressing genes involved in ion transporter activity and translation control. C. gigas activated genes associated with glycolipid metabolism while inhibiting cell division during acid stress. These findings suggested that C. ariakensis has evolved into a more energy-efficient regulatory network than C. gigas, incorporating both front-loading and responsive mechanisms to maintain acidbase homeostasis. This study is the first to investigate acid-tolerance differences between mollusks inhabiting estuarine and open coastal environments and provides critical insights into the resilience of mollusks in increasingly acidified oceans.

Selection of Sclerodermus pupariae Reference Genes for Quantitative Real-Time PCR

S. pupariae is a newly discovered species of parasitoid wasps. Research into its development, behavioral genetics, and molecular mechanisms provides valuable insights for improving integrated pest management strategies. Quantitative real-time PCR (qRT-PCR) is the most commonly used method for analyzing gene expression. This method requires the identification of stable reference genes to accurately evaluate transcriptional level variations. In this study, eight candidate reference genes (TUB, TBP, RPS18, GAPDH, 18S rRNA, RPL32, Actin, and EF1-α) were identified and evaluated for their suitability as reference genes. Gene expression levels across different developmental stages were analyzed using three software tools, GeNorm, NormFinder, and BestKeeper, and the online tool RefFinder. The overall ranking of reference gene stability was as follows: RPS18 > 18S rRNA > RPL32 > GAPDH > Actin > TUB > TPB > EF1-α. Ultimately, RPS18 was determined to be the most stable reference gene.

Two novel antimicrobial peptides P33-57 and mP168-187 from zebrafish showing potent antibacterial activities

It is known that overuse or abuse of antibiotics has undoubtedly accelerated the global antibiotic resistance crisis, and long-time use of antibiotics may have adverse effects on the health of animal, human, and ecosystem. Therefore, it is necessary to find antibiotic alternatives that can be used in aquaculture and are non-toxic to the human. Here we clearly demonstrated that both the PH and FYVE domain of Plekhf2 in zebrafish have antibacterial properties and can interact with PGN in this study. Therefore, we screened four candidate peptides from the two domains. It was demonstrated that P152-172 and P168-187 had no obvious antibacterial activities, while P33-57 and mP168-187 had strong antibacterial activities, which may be used as antimicrobial peptides. Additionally, transmission electron microscopy experiment revealed that P33-57 and mP168-187 can destroy the cell wall of bacteria, thereby directly killing bacteria. Importantly, it was found that P33-57 and mP168-187 had no hemolysis to red blood cells and lacked cytotoxicity. In summary, P33-57 and mP168-187could be seen as antibacterial activity centers of PLEKHF2 and may be promising antimicrobial peptides to combat bacterial infections facing an antibiotic-resistance crisis.

Evaluation of the biological function of ribosomal protein S18 from cattle tick Rhipicephalus microplus

Rhipicephalus (Boophilus) microplus, also known as the cattle tick, causes severe parasitism and transmits different pathogens to vertebrate hosts, leading to massive economic losses. In the present study, we performed a functional characterization of a ribosomal protein from R. microplus to investigate its importance in blood feeding, egg production and viability. Ribosomal protein S18 (RPS18) is part of the 40S subunit, associated with 18S rRNA, and has been previously pointed to have a secondary role in different organisms. Rhipicephalus microplus RPS18 (RmRPS18) gene expression levels were modulated in female salivary glands during blood feeding. Moreover, mRNA levels in this tissue were 10 times higher than those in the midgut of fully engorged female ticks. Additionally, recombinant RmRPS18 was recognized by IgG antibodies from sera of cattle naturally or experimentally infested with ticks. RNAi-mediated knockdown of the RmRPS18 gene was performed in fully engorged females, leading to a significant (29 %) decrease in egg production. Additionally, egg hatching was completely impaired, suggesting that no viable eggs were produced by the RmRPS18-silenced group. Furthermore, antimicrobial assays revealed inhibitory activities against gram-negative Escherichia coli and gram-positive Staphylococcus aureus bacteria, affecting bacterial growth. Data presented here show the important role of RmRPS18 in tick physiology and suggest that RmRPS18 can be a potential target for the development of novel strategies for tick control.

Soybean 40S Ribosomal Protein S8 (GmRPS8) Interacts with 6K1 Protein and Contributes to Soybean Susceptibility to Soybean Mosaic Virus

Soybean mosaic virus (SMV), a member of Potyvirus, is the most destructive and widespread viral disease in soybean production. Our earlier studies identified a soybean 40S ribosomal protein S8 (GmRPS8) using the 6K1 protein of SMV as the bait to screen a soybean cDNA library. The present study aims to identify the interactions between GmRPS8 and SMV and characterize the role of GmRPS8 in SMV infection in soybean. Expression analysis showed higher SMV-induced GmRPS8 expression levels in a susceptible soybean cultivar when compared with a resistant cultivar, suggesting that GmRPS8 was involved in the response to SMV in soybean. Subcellular localization showed that GmRPS8 was localized in the nucleus. Moreover, the yeast two-hybrid (Y2H) experiments showed that GmRPS8 only interacted with 6K1 among the eleven proteins encoded by SMV. The interaction between GmRPS8 and 6K1 was further verified by a bimolecular fluorescence complementation (BiFC) assay, and the interaction was localized in the nucleus. Furthermore, knockdown of GmRPS8 by a virus-induced gene silencing (VIGS) system retarded the growth and development of soybeans and inhibited the accumulation of SMV in soybeans. Together, these results showed that GmRPS8 interacts with 6K1 and contributes to soybean susceptibility to SMV. Our findings provide new insights for understanding the role of GmRPS8 in the SMV infection cycle, which could help reveal potyviral replication mechanisms.

Identification of zebrafish GIGYF2 presents in egg/embryo as an antibacterial protein

Previous studies have shown that GIGYF2 plays multiple roles, but its overall biological function remains poor-defined. Here we clearly demonstrated that zebrafish (Danio rerio) GIGYF2 has GYF domain and gigyf2 mainly expressed in caudal fin, brain, eyes and testis in a tissue specific manner, and was most abundant in brain and testis. GYF domain of GIGYF2 was a peptidoglycan (PGN), lipopolysaccharide (LPS)- and lipoteichoic acid (LTA)- binding protein abundantly stored in the testis/embryos of zebrafish, acting not only as a pattern recognition receptor, but also as an effector molecule, capable of inhibiting the growth of gram-positive and -negative bacteria. Furthermore, we reveal that the residues of GIGYF2 positioned at 582-601 and 848-865 were indispensable for GIGYF2 antibacterial activity. Additionally, site-directed mutation could improve antibacterial activities. Collectively, our results indicate that zebrafish GYF domain of GIGYF2 recognize bacterial characteristic molecules PGN, LPS and LTA, and directly kill bacteria as an antibacterial effector. This work also provides another angle for understanding the biological roles of GIGYF2.

Eukaryotic Ribosomal Protein S5 of the 40S Subunit: Structure and Function

The ribosomal protein RPS5 is one of the prime proteins to combine with RNA and belongs to the conserved ribosomal protein family. It plays a substantial role in the process of translation and also has some non-ribosome functions. Despite the enormous studies on the relationship between the structure and function of prokaryotic RPS7, the structure and molecular details of the mechanism of eukaryotic RPS5 remain largely unexplored. This article focuses on the structure of RPS5 and its role in cells and diseases, especially the binding to 18S rRNA. The role of RPS5 in translation initiation and its potential use as targets for liver disease and cancer are discussed.

Identification of zebrafish PLEKHF2 presents in egg/embryos as an antibacterial protein

PLEKHF2 proteins are widespread in animals, but their functions and mechanisms remain poorly defined. Here we clearly demonstrate that PLEKHF2 is a newly identified present abundantly in the eggs/embryos of zebrafish. We also show that recombinant PLEKHF2 acts as a pattern recognition receptor capable of identifying the bacterial signature molecule PGN, LPS, and LTA, binding the bacteria, and functions as an antibacterial effector directly killing the bacteria. In brief, these results indicate that PLEKHF2 is an antibacterial protein, a novel role assigned to PLEKHF2 proteins.