Molecular characterization, expression profiling, and functional analysis of prohibitin 1 in red seabream, Pagrus major.

Prohibitin 1 (PHB1) is ubiquitously expressed in multiple compartments within cells and is involved in the cell cycle, cell signaling, apoptosis, transcriptional regulation, and mitochondrial biogenesis at the cellular level and in the inflammation-associated and immunological functions of B and T lymphocytes. PHB1 is an important protein that performs antioxidant regulation and immune functions inside and outside cells but has not been sufficiently studied in teleost fish. Our study aimed to elucidate the functional properties and gain new insights into the biological processes and immune system of red seabream (Pagrus major), a commercially important fish cultured in South Korea and East Asia. PHB1 mRNA was most abundantly expressed in the head kidney of healthy red seabream, and significant changes in its expression were observed after artificial infection with bacteria and viruses. On analysis, reporter gene was also significantly upregulated by polyinosinic-polycytidylic acid, lipopolysaccharides, and hydrogen peroxide. Consequent to the functional characterization of PHB1 in cells via recombinant protein preparation, the activity of leukocytes was enhanced and the reactive oxygen species-induced stress in red blood cells was reduced. The results reveal the functional characteristics of PHB1 and provide new insights into the biological processes and immune system of P. major, with beneficial implications in the study of stress responses.

Red Sea Bream Iridovirus (RSIV) Kinetics in Rock Bream (Oplegnathus fasciatus) at Various Fish-Rearing Seawater Temperatures.

Red sea bream iridoviral disease (RSIVD) causes serious economic losses in the aquaculture industry. In this paper, we evaluated RSIV kinetics in rock bream under various rearing water temperatures and different RSIV inoculation concentrations. High viral copy numbers (approximately 103.7-106.7 RSIV genome copies/L/g) were observed during the period of active fish mortality after RSIV infection at all concentrations in the tanks (25 °C and 20 °C). In the group injected with 104 RSIV genome copies/fish, RSIV was not detected at 21-30 days post-infection (dpi) in the rearing seawater. In rock bream infected at 15 °C and subjected to increasing water temperature (1 °C/d until 25 °C) 3 days later, the virus replication rate and number of viral copies shed into the rearing seawater increased. With the decrease in temperature (1 °C/d) from 25 to 15 °C after the infection, the virus replicated rapidly and was released at high loads on the initial 3-5 dpi, whereas the number of viral copies in the fish and seawater decreased after 14 dpi. These results indicate that the number of viral copies shed into the rearing seawater varies depending on the RSIV infection level in rock bream.

Red sea bream interleukin (IL)-1ß and IL-8 expression, subcellular localization, and antiviral activity against red sea bream iridovirus (RSIV).

Interleukin-1 beta (IL-1ß) is transcribed by monocytes, macrophages, and dendritic cells in response to activation of toll-like receptors (TLRs) by pathogen-associated molecular patterns (PAMPs) or cytokine signalling and causes a rapid inflammatory response to infection. IL-8, also known as chemokine C-X-C motif ligand (CXCL)-8, is regulated by IL-1ß and affects the chemotaxis of macrophages and neutrophils upon pathogen infection. In healthy red sea bream, rsbIL-1ß is most highly distributed in the liver, and rsbIL-8 is most highly distributed in the head kidney. In response to RSIV infection, rsbIL-1ß and rsbIL-8 mRNA are significantly upregulated in the kidney and spleen. This may be because the primary infection targets of RSIV are the kidney and spleen. In the gills, both genes were significantly upregulated at 7 days after RSIV infection and may be accompanied by a cytokine storm. In the liver, both genes were significantly downregulated at most observation points, which may be because the immune cells such as macrophages and dendritic cells expressing rsbIL-1ß or rsbIL-8 migrated to other tissues because the degree of RSIV infection was relatively low. Using a GFP fusion protein, it was confirmed that rsbIL-1ß and rsbIL-8 were localized to the cytoplasm of Pagrus major fin (PMF) cells. RsbIL-1ß overexpression induced the expression of interferon gamma (IFN-γ), myxovirus-resistance protein (Mx) 1, IL-8, IL-10, TNF-α, and MyD88, while rsbIL-8 overexpression induced the expression of IFN-γ, Mx1, rsbIL-1ß and TNF-α. In addition, overexpression of both genes significantly reduced the genome copies of RSIV and significantly reduced the viral titers. Therefore, rsbIL-1ß and rsbIL-8 in red sea bream play an antiviral role against RSIV through their normal signalling.

Molecular characterization and expression analysis of septin gene family and phagocytic function of recombinant septin 2, 3 and 8 of starry flounder (Platichthys stellatus).

Septin is an evolutionarily conserved family of GTP-binding proteins. Septins are known to be involved in a variety of cellular processes, including cell division, chromosome separation, cell polarity, motility, membrane dynamics, exocytosis, apoptosis, phagocytosis, DNA damage responses, and other immune responses. In this study, the sequences of the septin gene family of starry flounder were obtained using NGS sequencing, and the integrity of the sequences was verified through cloning and sequencing. At first, the amino acid sequence was annotated using the cDNA sequence, and then, the gene sequence was verified through multiple sequence alignment and phylogenetic analyses using the related conserved sequences. The septin gene family was classified into three subgroups based on the phylogenetic analysis. High conservation within the domain and homology between the genes reported in different species were confirmed. The expression level of septin gene family mRNA in each tissue of healthy starry flounder was evaluated to confirm the tissue- and gene-specific expression levels. Additionally, as a result of the analysis of mRNA expression after simulated pathogen infection, significant expression changes and characteristics were confirmed upon infection with bacteria (Streptococcus parauberis PH0710) and virus (VHSV). Based on the current results and that of previous studies, to confirm the immunological function, Septin 2, 3, and 8 were produced as recombinant proteins based on the amino acid sequences, and their role in phagocytosis was further investigated. The results of this study indicate that septin gene family plays a complex and crucial role in the host immune response to pathogens of starry flounder.

Physicochemical Characteristics and Occupational Exposure of Silica Particles as Byproducts in a Semiconductor Sub Fab.

This study aimed to elucidate the physicochemical characteristics and occupational exposure of silica powder and airborne particles as byproducts generated from the first scrubbers of chemical vapor deposition and diffusion processes during maintenance in a semiconductor facility sub fab to reduce unknown risk factors. The chemical composition, size, morphology, and crystal structure of powder and airborne particles as byproducts were investigated using a scanning electron microscopy and transmission electron microscopy equipped with an energy dispersive X-ray spectroscopy, and an X-ray diffraction. The number and mass concentration measurements of airborne particles were performed by using an optical particle sizer of a direct-reading aerosol monitor. All powder and airborne particle samples were mainly composed of oxygen (O) and silicon (Si), which means silica. The byproduct particles were spherical and/or nearly spherical and the particle size ranged from 10 to 90 nm, based on primary particles. Most of the particles were usually agglomerated within a particle size range from approximately 100 nm to 35 µm. In addition, most of the powder samples exhibited diffraction patterns with a broad and relatively low intensity at 2θ degrees 21.6-26.7°, which is similar to that of pure amorphous silica. The above results show the byproduct particles are amorphous silica, which are considered a less toxic foam compared to crystalline silica. The number and mass concentrations of PM10 (particles less than 10 µm in diameter) ranged from 4.250-78.466 particles/cm3 and 0.939-735.531 µg/m3, respectively. In addition, 0.3-1.0 and 2.5-10 µm particles occupied the highest portion of the number and mass concentrations, respectively. Meanwhile, several peak exposure patterns were observed at a specific step, which is the process of removing powder particles on the inner chamber and cleaning the chamber by using a vacuum cleaner and a clean wiper, during the maintenance task.

First report of eosinophil peroxidase in starry flounder (Platichthys stellatus): Gene identification and gene expression profiling.

Eosinophils are granular leukocytes that are evolutionarily preserved in the innate immune system of some invertebrates and vertebrates, and these cells can directly remove invading microorganisms and secrete various cytokines, and are also involved in homeostasis. These eosinophils are made up of specific granular proteins that can be differentiated from other cells, and eosinophil peroxidase (EPX) is a peroxidase released only from eosinophils that plays an important role in maintaining the main function and homeostasis of eosinophils. We obtained the sequence information of EPX for the first time from the starry flounder (Platichthys stellatus), and predicted it by amino acid sequencing to confirm sequence alignment and phylogenetic characteristics with other species. Based on analysis of the expression characteristics of PsEPX mRNA in healthy P. stellatus, it was expressed at the highest level in peripheral blood lymphocytes (PBLs) and was also expressed at a relatively high level in the head kidney and intestine, which are immune-related tissues. After artificial infection with Streptococcus parauberis and viral haemorrhagic septicaemia virus, which are the causes of major pathogenic diseases, the expression level of PsEPX was significantly regulated, which showed specific characteristics of pathogens or tissues. These results suggest that PsEPX is an important component of the immune system of P. stellatus and is considered a basic research case for the study of the immunological function of eosinophils in fish.

Molecular Identification and mRNA Expression Profiles of Galectin-9 Gene in Red Sea Bream (Pagrus major) Infected with Pathogens.

Galectin (Gal) is a member of a family of ß-galactoside-binding lectin. The members of this family play important roles in the recognition of carbohydrate ligands and in various other biological processes. In this study, we identified the gene encoding Gal-9 in Pagrus major (PmGal-9) and analyzed its expression in various tissues after pathogen challenge. Alignment analysis revealed that the two galactose-binding lectin domains of the deduced protein were highly conserved among all the teleosts. Phylogenetic analysis revealed that PmGal-9 is most closely related to the Gal-9 gene of gilthead sea bream. PmGal-9 was ubiquitously expressed in all tissues analyzed but was predominantly expressed in the spleen, head kidney, and intestine. After challenges with major microbial pathogens (Edwardsiella piscicida, Streptococcus iniae, or red sea bream iridovirus) of red sea bream, PmGal-9 mRNA expression was significantly regulated in most immune-related tissues. These results suggested that PmGal-9 not only plays an important role in the immune system of red sea bream but is also a possible inflammatory marker for pathogenic diseases.

Functional characterization and gene expression profile of perforin-2 in starry flounder (Platichthys stellatus).

The membrane attack complex/perforin (MACPF) superfamily consists of multifunctional proteins that form pores on the membrane surface of microorganisms to induce their death and have various immune-related functions. PFN2 is a perforin-like protein with an MACPF domain, and humans with deficient PFN2 levels have increased susceptibility to bacterial infection, which can lead to fatal consequences for some patients. Therefore, in this study, we confirmed the antimicrobial function of PFN2 in starry flounder (Platichthys stellatus). The molecular properties were confirmed based on the verified amino acid sequence of PsPFN2. In addition, the expression characteristics of tissue-specific and pathogen-specific PsPFN2 mRNA were also confirmed. The recombinant protein was produced using Escherichia coli, and the antimicrobial activity was then confirmed. The coding sequence of PFN2 (PsPFN2) in P. stellatus consists of 710 residues. The MACPF domain was conserved throughout evolution, as shown by multiple sequence alignment and phylogenetic analysis. PsPFN2 mRNA is abundantly distributed in immune-related organs such as the spleen and gills of healthy starry flounder, and significant expression changes were confirmed after artificial infection by bacteria or viruses. We cloned the MACPF domain region of PFN2 to produce a recombinant protein (rPFN2) and confirmed its antibacterial effect against a wide range of bacterial species and the parasite (Miamiensis avidus).

The First Detection of Kudoa hexapunctata in Farmed Pacific Bluefin Tuna in South Korea, Thunnus orientalis (Temminck and Schlegel, 1844).

The consumption of fish and shellfish worldwide is steadily increasing, and tuna is a particularly valuable fish species. However, infection caused by Kudoa spp. is causing problems in many fish including the Pacific bluefin tuna (Thunnus orientalis), and there is much controversy about the association of these infections with foodborne disease. In this study, using haematological and histological analyses of the blood and internal organs (liver, spleen, kidney, heart, stomach, intestine, gill, and muscle) of Pacific bluefin tuna cultured in South Korea, infection with Myxosporea was first identified, and molecular biological analysis was conducted. In this study, Kudoa hexapunctata was finally identified. The Pacific bluefin tunas analysed in this study did not show any gross pathology lesions, such as visible cysts and/or myoliquefaction, of infection with this species. The histological analytical results can provide guidelines for the identification of K. hexapunctata. In the case of K. hexapunctata-induced infection, unlike other countries, such as Japan, there have been no reports in South Korea, and this study is the first to detect K. hexapunctata infection in Pacific bluefin tuna cultured in South Korea. The correlation between K. hexapunctata and food poisoning is not yet clear, however, it is thought that continuous observation of its infection is necessary.

The molecular characterization, expression analysis and antimicrobial activity of theromacin from Asian polychaeta (Perinereis linea).

Antimicrobial peptides (AMPs) are molecular factors in innate immunity and are believed to play a key role in invertebrate host defence. We identified theromacin (TM) from an Asian polychaeta, Perinereis linea, using de novo RNA-seq analysis. TM, a typical AMP of invertebrates, is a cysteine-rich AMP with five disulfide bonds consisting of ten cysteine residues. In gene expression analysis, TM genes were constantly upregulated after lipopolysaccharide (LPS) stimulation. In contrast, after peptidoglycan (PGN) stimulation, it was upregulated initially and downregulated after 12 h. We synthesized a peptide based on the macin AMP in the TM amino acid sequence. The synthetic peptide showed antibacterial activity against some Gram-positive and Gram-negative bacteria. Therefore, the AMPs of P. linea might have broad roles in host defence and exhibit different degrees of activity.

Two short antimicrobial peptides derived from prosaposin-like proteins in the starry flounder (Platichthys stellatus).

Prosaposin (PSAP) is a precursor of saposin (SAP), which is present in lysosomal and secreted proteins. PSAP is a member of the SAP-like protein families, which comprise multifunctional proteins. In particular, their antimicrobial activity has been reported. We identified PSAP-like (PsPSAPL) sequences from starry flounder and analysed their expression and antimicrobial activity based on cDNA and amino acid sequences. PsPSAPL showed conservation of three saposin B type domains at high levels, and PsPSAPL mRNA was relatively abundantly distributed in the brain and gills of healthy starry founders. PsPSAPL mRNA showed significant expression changes in response to viral haemorrhagic septicaemia virus and Streptococcus parauberis. Synthetic peptides (PsPSAPL-1 and -2), prepared based on amino acid sequences, were used to confirm as well as analyse the antimicrobial activity against bacteria and parasites. Consequently, PsPSAPL-1 and -2 were found to significantly inhibit the growth of various bacteria and kill the Miamiensis avidus. In addition, bacterial biofilm formation was significantly inhibited. Safety was also confirmed by analysing cell haemolysis. These results indicate the immunological function of PsPSAP and the potential antimicrobial activity of the AMPs PsPSAPL-1 and -2.

Molecular genetic characterisation and expression profiling of calpain 3 transcripts in red sea bream (Pagrus major).

Calpains (CAPNs) belong to the papain superfamily of cysteine proteases, and they are calcium-dependent cytoplasmic cysteine proteases that regulate a variety of physiological processes. We obtained the sequence of CAPN3 from an NGS-based analysis of Pagrus major (PmCAPN3) and confirmed the conserved molecular biological properties in the predicted amino acid sequence. The amino acid sequence and predicted domains of CAPN3 were found to be highly conserved in all of the examined species, and one catalytic domain and four calcium binding sites were identified. In healthy P. major, the PmCAPN3 mRNA was most abundantly expressed in the muscle and skin, and ubiquitously expressed in the other tissues used in the experiment. After artificial infections with fish pathogens, significant changes in its expression levels were found in immune-related tissues, most of showed upregulation. In particular, the highest level of expression was found in the liver, a tissue associated with protease activity. Taken together, these results suggest a physiological activity for PmCAPN3 in P. major and reveal functional possibilities that have not yet been reported in the immune system.

Relationship Between Obesity and Balance in the Community-Dwelling Elderly Population: A Cross-Sectional Analysis.

INTRODUCTION: Although there are similar characteristics between obese individuals and fall-susceptible population, little is known about relationships between body weight and risk factors for fall, particularly in the elderly population. The aim of this study was to determine whether body mass index-based obesity is associated with decreased balance and whether instability has relationships with the main risk factors for falls. METHODS: A total of 317 participants were categorized based on their body mass index. Clinical balance assessments were performed using the Berg Balance Scale, Timed Up and Go test, and Short Physical Performance Battery. The knee extensor strength of each individual was measured using a dynamometer. Total sway distance was calculated on InBody posturography in four conditions. RESULTS: The results of three clinical balance assessment tools showed significant correlation with body mass index. The obese group showed decreased isokinetic knee extensor muscle strength and had a higher total sway distance than the normal weight group. CONCLUSIONS: The elderly population with obesity exhibits poor balance performing ability, and it is associated with the decreased strength of the lower limbs and impaired postural stability. The logistic regression analysis of our study showed that body mass index-based obesity can be regarded as a fall risk.

Correlations between swallowing function and acoustic vowel space in stroke patients with dysarthria.

BACKGROUND: Dysphagia and dysarthria tend to coexist in stroke patients. Dysphagia can reduce patients' quality of life, cause aspiration pneumonia and increased mortality. OBJECTIVE: To evaluate correlations among swallowing function parameters and acoustic vowel space values in patients with stroke. METHODS: Data from stroke patients with dysarthria and dysphagia were collected. The formant parameter representing the resonance frequency of the vocal tract as a two-dimensional coordinate point was measured for the /a/, /ae/, /i/, and /u/vowels, and the quadrilateral vowel space area (VSA) and formant centralization ratio (FCR) were measured. Swallowing function was evaluated by a videofluoroscopic swallowing study (VFSS) using the videofluoroscopic dysphagia scale (VDS) and penetration aspiration scale (PAS). Pearson's correlation and linear regression analyses were used to assess the correlation of VSA and FCR to VDS and PAS scores. RESULTS: Thirty-one stroke patients with dysphagia and dysarthria were analyzed. VSA showed a negative correlation to VDS and PAS scores, while FCR showed a positive correlation to VDS score, but not to PAS score. VSA and FCR were significant factors for assessing dysphagia severity. CONCLUSIONS: VSA and FCR values were correlated with swallowing function and may be helpful in predicting dysphagia severity associated with stroke.

Correlations Between Values of Articulation Tests and Language Tests for Children With Articulation Disorder in Korea.

OBJECTIVE: To evaluate correlations between values of articulation tests and language tests for children with articulation disorder in Korea. METHODS: Data of outpatients with chief complaint of an articulation problem were retrospectively collected. Patients who underwent Urimal Test of Articulation and Phonation (U-TAP) with Assessment of Phonology and Articulation for Children (APAC), Preschool Receptive-Expressive Language Scale (PRES), or Receptive and Expressive Vocabulary Test (REVT) simultaneously were identified. Patients whose word-level percentages of correct consonants in U-TAP (UTAP_wC) were more than 2 standard deviations below the mean as diagnostic criteria for articulation disorder were selected. Those whose receptive language age (P_RLA), expressive language age (P_ELA), or combined language age (P_CLA) in PRES was delayed more than 24 months compared to their chronological age in months as diagnostic criteria for language disorder were excluded. RESULTS: Thirty-three children aged 3-6 years were enrolled retrospectively. PRES and U-TAP showed significant correlations for most of value relationships. PRES and APAC showed significant correlations for all value relationships except for receptive language age. All values of REVT were significantly correlated with all values from U-TAP, but not with any value from APAC. Articulation tests U-TAP and APAC showed significant correlations between percentages of correct consonants. Language tests PRES and REVT showed significant correlations for all value relationships. CONCLUSION: This study suggests that articulation abilities and language abilities might be correlated in children with articulation disorder.

The atypical chemokine receptor 4 in red sea bream (Pagrus major): Molecular characterization and gene expression analysis.

Atypical chemokine receptor 4 (ACKR4) is regulated by cytokines, binds chemokines and regulates the chemokine gradient. We verified the cDNA sequence by confirming ACKR4 from red sea bream (PmACKR4) by next generation sequencing (NGS) and analysed the molecular characteristics and gene expression profile. In the analysis using the predicted amino acid sequence of PmACKR4, a highly conserved G protein-coupled receptor 1 region and two cysteine residues were identified and included in the ACKR4 teleost cluster in the phylogenetic analysis. In healthy red sea bream, PmACKR4 mRNA was expressed at the highest levels in head kidney and was upregulated in all immune -related tissues used in the experiment after challenges with Streptococcus iniae (S. iniae) and red sea bream iridovirus (RSIV). These results suggest that ACKR4 is highly conserved in red sea bream and may play an important role in the immune system as previously reported. It is thought that ACKR4 acts as a regulator of immune -related cells via immune reactions after pathogenic infection.

Functional analysis and gene expression profiling of extracellular cathepsin Z in red sea bream, Pagrus major.

Cathepsin Z (CTSZ) is a lysosomal cysteine protease that is known to be involved in the maintenance of homeostasis and the biological mechanisms of immune cells. In this study, we have confirmed the tissue specific expression of the cathepsin Z (PmCTSZ) gene in Pagrus major, and confirmed its biological function after producing recombinant protein using Escherichia coli (E. coli). Multiple sequence alignment analysis revealed that the active site of the cysteine proteases and three N-glycosylation sites of the deduced protein sequence were highly conserved among all of the organisms. Phylogenetic analysis revealed that PmCTSZ was included in the clusters of CTSZ and the cysteine proteases of other bony fish and is most closely related to Japanese flounder CTSZ. PmCTSZ was distributed in all of the tissues from healthy red sea bream that were used in the experiment and was most abundantly found in the spleen and gill. Analysis of mRNA expression after bacterial (Edwardsiella piscicida: E. piscicida and Streptococcus iniae: S. iniae) or viral (red seabream iridovirus: RSIV) challenge showed significant gene expression regulation in immune-related tissues, but they maintained relatively normal levels of expression. We produced recombinant PmCTSZ (rPmCTSZ) using an E. coli expression system and confirmed the biological function of extracellular rPmCTSZ in vitro. We found that bacterial proliferation was significantly inhibited by rPmCTSZ, and the leukocytes of red sea bream also induced apoptosis and viability reduction.

Data on molecular characterization and expression profiles of the NF-κB repressing factor gene in red sea bream (Pagrus major).

Nuclear factor-kappaB (NF-κB) repressing factor (NKRF) specifically inhibits the transcriptional activity of NF-κB protein. The PmNKRF cDNA is composed of 757 amino acid residues. Alignment analysis revealed that the G-patch and R3H domains are conserved in different organisms. We aimed to analyse red sea bream NKRF (PmNKRF) gene expression after infection with pathogens [Streptococcus iniae or red sea bream iridovirus (RSIV)] and in healthy individuals. In healthy individuals, PmNKRF was ubiquitously expressed in all 12 tested tissues, predominantly in the head kidney and spleen. Expression of PmNKRF was significantly up-regulated in the gills, kidney, liver and spleen after RSIV infection. After S. iniae infection, PmNKRF expression was significantly down-regulated in the gills and significantly up-regulated in the kidney, liver and spleen.

Characterization of gene expression profiles and functional analysis of peptidoglycan recognition protein 2 from rock bream (Oplegnathus fasciatus).

Peptidoglycan recognition protein 2 (PGRP2) is a Zn2+-dependent peptidase that plays important roles in binding to microbial components of the cell membrane, inducing phagocytosis and antimicrobial activity. Rock bream (Oplegnathus fasciatus) PGRP2 (RbPGRP2) was identified in the intestine by next generation sequencing (NGS) analysis. The open reading frame (ORF) the RbPGRP2 cDNA (470 amino acid residues) contains a peptidoglycan recognition protein domain (residues 300 to 446). Alignment analysis revealed that RbPGRP2 shares 37.6-53.5% overall sequence identity with the PGRP2s of other species. Phylogenetic analysis revealed that RbPGRP2 clustered together with PGRP2s from teleosts. In healthy rock bream, RbPGRP2 was found to be ubiquitously expressed in all of the examined tissues, especially in the liver. RbPGRP2 expression was significantly upregulated in all of the examined tissues of rock bream after infection with Edwardsiella piscicida, Streptococcus iniae and red sea bream iridovirus (RSIV) compared with the control. Purified rRbPGRP2 interactions with bacteria and inhibited the growth of bacteria in the presence of Zn2+. These results indicate that RbPGRP2 plays an important role in the innate immune response against bacterial infection.

Molecular characterization, expression and functional analysis of peptidoglycan recognition protein-SC2 from rock bream, Oplegnathus fasciatus.

Peptidoglycan recognition proteins are members of the family of pattern recognition receptors (PRRs), that play important roles in the recognition of peptidoglycan and various biological processes. In this study, we have characterized peptidoglycan recognition protein-SC2 (PGRP-SC2) in rock bream (Oplegnathus fasciatus) (RbPGRP-SC2) and analysed its expression in various tissues after pathogen challenge. A sequence alignment revealed that the residues essential to zinc binding of the deduced protein were highly conserved among all the organisms. Phylogenetic analysis revealed that RbPGRP-SC2 is most closely related to the large yellow croaker PGRP-SC2. RbPGRP-SC2 was ubiquitously expressed in all tissues analysed, predominantly distributed in muscle and skin. After challenge with microbial pathogens (Edwardsiella piscicida), Streptococcus iniae or red seabream iridovirus [RSIV]), RbPGRP-SC2 was up-regulated in all the tissues examined, especially in liver. We produced recombinant RbPGRP-SC2 (rRbPGRP-SC2) using an Escherichia coli expression system. The rRbPGRP-SC2 had agglutination activity towards both Gram-negative (E. piscicida) and Gram-positive bacteria (S. iniae). In addition, rRbPGRP-SC2 induced leukocyte apoptosis and promoted leukocyte phagocytosis. These results suggest that the RbPGRP-SC2 plays an important role in the immune system and in maintaining cellular homeostasis of rock bream.