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

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.