Identification of parvalbumin-like protein as a major protein of common carp (Cyprinus carpio L) spermatozoa which appears during final stage of spermatogenesis

Proteomic analysis of carp seminal plasma provides insights into the immune response to bacterial infection of the male reproductive system

Aeromonas salmonicida is recognized as a significant bacterial pathogen in ulcerative disease of cyprinid fish. However, the mechanism of immunity to these bacteria in common carp is still not well understood, especially the immune regulation in the gonad to bacterial infection. The aims of our study were to analyze changes in the seminal plasma proteome following A. salmonicida infection in carp males. The observed pathological changes in the tissue (liver, spleen, kidney and testis) morphology and upregulation of immune-related genes (tnfa2, il6a) confirmed the successful infection challenge. Using mass spectrometry-based label-free quantitative proteomics, we identified 1402 seminal plasma proteins, and 44 proteins (20 up- and 24 downregulated) were found to be differentially abundant between infected and control males. Most differentially abundant proteins were involved in the immune response mechanisms, such as acute phase response, complement activation and coagulation, inflammation, lipid metabolism, cell-cell and cell-matrix adhesion, creatine-phosphate biosynthesis and germ cell-Sertoli cell junction signaling. Bacterial infection also caused profound changes in expression of selected genes in the testis and hematopoietic organs, which contributed to changes in seminal proteins. The altered seminal proteins and bacterial proteins in seminal plasma may serve as valuable markers of infection in the testis.

Proteomic and metabolomic insights into the functions of the male reproductive system in fishes

Proteomics and metabolomics are emerging and powerful tools to unravel the complex molecular mechanisms regulating reproduction in male fish. So far, numerous proteins and metabolites have been identified that provide us with valuable information to conduct a comprehensive analysis on seminal plasma and spermatozoa components and their functions. These analyses have allowed a better understanding of the blood-testis barrier functions, the molecular mechanisms underlying spermatogenesis, spermatozoa maturation, motility signaling, and competition as well as the mechanism of cryodamage to sperm structure and functions. To extend, proteins that undergo posttranslational modification, such as phosphorylation and oxidation in response to spermatozoa motility activation and cryopreservation, respectively, have been identified. Proteomic studies resulted in identification of potential proteins that can be used as biomarkers for sperm quality and freezability to enable the control of artificial reproduction, and to improve methods for long-term preservation (cryopreservation) of sperm. The different proteins expressed in the spermatozoa of neomales and normal males can also provide new insights into development of methods for separating X and Y fish sperm, and changes in the protein profiles in haploid and diploid spermatozoa will provide new perspectives to better understand the mechanism of male polyploidy. Overall, the knowledge gained by proteomic and metabolomic studies is important from basic to applied sciences for the development and/or optimisation of techniques in controlled fish reproduction.

Proteomic characterization of fresh spermatozoa and supernatant after cryopreservation in relation to freezability of carp (Cyprinus carpio L) semen

Our recent studies suggested that the freezability of carp semen is related to seminal plasma protein profiles. Here, we aimed to compare the spermatozoa proteomes of good (GF) and poor (PF) freezability semen of carp. To achieve this, we used two-dimensional difference in gel electrophoresis followed by MALDI-TOF/TOF mass spectrometry. The semen was classified as GF or PF based on sperm motility after freeze/thawing. We identified proteins enriched in spermatozoa of GF (22 proteins) and PF (18 proteins) semen. We also identified 12 proteins enriched in the supernatant after cryopreservation of PF semen. Good freezability is related to high concentrations of proteins involved in the maintenance of flagella structure, membrane fluidity, efficient control of Ca²⁺ and sperm motility, energy production, and antioxidative protection, which likely reflects the full maturation status of spermatozoa of GF semen. On the other hand poor freezability seems to be related to the presence of proteins identified as released in high quantities from cryopreserved sperm of PF. Thus, the identified proteins might be useful bioindicators of freezing resilience and could be used to screen carp males before cryopreservation, thus improve long-term sperm preservation in carp. Data are available via ProteomeXchange with identifier PXD008187.

Oligomeric protein complexes of apolipoproteins stabilize the internal fluid environment of organism in redfins of the Tribolodon genus [Pisces; Cypriniformes, Cyprinidae]

One of the most important functions of plasma proteins in vertebrates is their participation in osmotic homeostasis in the organism. Modern concepts about plasma proteins and their capillary filtration are based on a model of large monomeric proteins that are able to penetrate the interstitial space. At the same time, it was revealed that a considerable amount of oligomeric complexes are present in the low-molecular-weight (LM) protein fraction in the extracellular fluids of fishes. The functions of these complexes are unknown. In the present study, we investigated the LM-fraction proteins in the plasma and interstitial fluid (IF) of redfins of the genus Tribolodon. This fish alternatively spends parts of its life cycle in saline and fresh waters. We identified the protein Wap65, serpins and apolipoproteins in this fraction. By combining the methods of 2D-E under native and denaturing conditions with MALDI, we demonstrated that only apolipoproteins formed complexes. We showed that serum apolipoproteins (АроА-I, Аро-14) were present in the form of homooligomeric complexes that were dissociated with the release of monomeric forms of proteins in the course of capillary filtration to IF. Dissociation of homooligomers is not directly correlated with the change in salinity but is correlated with seasonal dynamics. We found that there was a significant decrease in the total protein concentration in IF relative to plasma. Therefore, we suggested that dissociation of homooligomeric complexes from various apolipoproteins supports the isoosmoticity of extracellular fluids relative to capillary wall stabilization through a fluid medium in fish.

De novo Assembly and Analysis of the Chilean Pencil Catfish Trichomycterus areolatus Transcriptome

Trichomycterus areolatus is an endemic species of pencil catfish that inhabits the riffles and rapids of many freshwater ecosystems of Chile. Despite its unique adaptation to Chile's high gradient watersheds and therefore potential application in the investigation of ecosystem integrity and environmental contamination, relatively little is known regarding the molecular biology of this environmental sentinel. Here, we detail the assembly of the Trichomycterus areolatus transcriptome, a molecular resource for the study of this organism and its molecular response to the environment. RNA-Seq reads were obtained by next-generation sequencing with an Illumina® platform and processed using PRINSEQ. The transcriptome assembly was performed using TRINITY assembler. Transcriptome validation was performed by functional characterization with KOG, KEGG, and GO analyses. Additionally, differential expression analysis highlights sex-specific expression patterns, and a list of endocrine and oxidative stress related transcripts are included.

Motility of carp spermatozoa is associated with profound changes in the sperm proteome

In freshwater cyprinids, spermatozoa are quiescent in seminal plasma and sperm motility is initiated by a decrease in osmolality (hypo-osmotic shock) after discharge into the aqueous environment. However, it is unknown at present if and to what extent changes in proteins are involved in carp sperm motility. Therefore, the aim of our study was to identify proteins related to carp sperm motility through a comparison of immobilized and activated carp spermatozoa using a 2D-DIGE approach. Our results, for the first time indicated that carp sperm motility is associated with changes in protein content. Seventy-two differentially expressed proteins were identified. These proteins are mainly involved in ubiquitin-proteasome pathways, glycolysis, the TCA cycle, remodeling and are putatively related to sperm energy metabolism and motility. Moreover proteins associated with oxidative stress responses, signal transduction by Ca(2+)-dependent MAPK cascades, and PKC and protein folding have been identified. The proteins involved in carp sperm motility were localized to the cytoplasm, mitochondria, cytoskeleton, nucleus and sperm membrane. The identification of a high number of proteins involved in carp sperm motility would contribute to current knowledge about the molecular mechanisms of sperm motility in freshwater fish.

BIOLOGICAL SIGNIFICANCE

To the best of our knowledge, few changes in proteins involved in the initiation of fish sperm motility have been identified. This is a limited number of proteins compared with the 80 recently identified proteins involved in human sperm motility. However, no proteomic studies of sperm motility have yet been performed on freshwater fish. Our present study allowed for the first time a comprehensive characterization of the proteins associated with carp sperm motility and a better understanding of the molecular mechanisms underlying sperm motility activation and maintenance. The application of 2D-DIGE facilitated the identification proteins crucial for sperm structural organization and motility. The identification of a high number of proteins involved in carp sperm motility would contribute appreciably to the presently limited information available on the mechanisms of sperm motility in freshwater fish. Moreover the identified list of proteins will create a platform for future studies designed to assess the functional significance of specific proteins in sperm motility.

Characterization, expression and antibacterial properties of apolipoproteins A from carp (Cyprinus carpio L.) seminal plasma

Apolipoproteins A are multifunctional proteins that, in addition to contributing to lipid metabolism and transport, are associated with the innate immune system in fish. Using a three step isolation procedure consisting of affinity chromatography on Blue-Sepharose, delipidation and reverse phase HPLC we isolated apolipoproteins from carp seminal plasma and identified them as ApoA-I and Apo-14 kDa. Moreover, we provided the full-length cDNA sequence of ApoA-I encoding 257 amino acids including a 18 amino acid signal peptide and a 4 amino acid propeptide. Apolipoproteins corresponded to the most abundant proteins in carp seminal plasma. Both ApoA-I and Apo-14 kDa were represented by several proteoforms that differ both in molecular mass and isoelectric point. The proteoforms of ApoA-I characteristic for seminal plasma were distinguished from those of blood. Carp seminal plasma ApoA-I and Apo-14 kDa showed a high immunologic similarity to their counterparts in carp blood and seminal plasma of other Cyprinid species. The mRNA expression analysis and immunohistochemical study suggest synthesis and secretion of ApoA-I and Apo-14 kDa in the fish reproductive tract and suggest a role in spermatogenesis and the stabilization of sperm membrane. Moreover, ApoA-I displayed bactericidal activity against Escherichia coli and bacteriostatic activity against Aeromonas hydrophila which suggests that ApoA-I is associated with innate immune system of the fish reproductive tract.

Isolation, characterisation and cDNA sequencing of a new form of parvalbumin from carp semen

Parvalbumins (Pv) are calcium-binding proteins present mainly in the muscle and nervous system where they act as a Ca2+ buffer. Our previous work demonstrated the presence of Pv-I in carp semen and indicated the presence of a second Pv (Pv-II). The purpose of the present work was to identify, purify and determine the full-length cDNA sequence of Pv-II from carp testis. Pv-II from seminal plasma was purified by ion-exchange chromatography (IEC) and preparative electrophoresis, while the Pv-II from spermatozoa was purified by IEC, gel filtration and preparative electrophoresis. The purified Pv-II was submitted to an analysis of molecular mass, isoelectric point (pI), amino-acid sequence and oligomerisation ability. The amino-acid sequence was used to construct primers and obtain the full-length cDNA sequence of seminal-specific Pv-II from carp testis. Analysis of the cDNA sequence indicated that carp-testis Pv-II was distinct from carp-muscle parvalbumins. Pv-II was distinct from Pv-I regarding sequence, molecular mass and pI. Both parvalbumins had the ability to form oligomers or to bind to other proteins. Carp seminal plasma had a protective effect against parvalbumin oligomerisation. Pv-II underwent post-translational modification such as n-acetylation and cysteinylation. The present study is the first to report the full-length cDNA sequence of parvalbumin from carp testis.

Identification of calcium-binding proteins in fish seminal plasma

Calcium ions play an important role in the activation of fish sperm movement. The mechanism of their binding in semen is still unknown. The goal of this study was the development of a method for identifying calcium-binding proteins in fish seminal plasma. Two methods of calcium-binding proteins detection were tested with the use of Quin2 and Stains-all dyes. The first method was useful for the identification of calcium-binding proteins of fish seminal plasma. It consisted of proteins separation using SDS-PAGE, transfer on PVDF membrane, incubation with CaCl₂, staining with Quin2 and illumination with UV light to reveal calcium-binding protein bands. Using Quin2 allowed the detection of calcium-binding proteins with low and high molecular weight. Electrophoretic species-specific profiles of calcium-binding proteins were identified in the seminal plasma of carp, whitefish, roach, brook trout, brown trout and rainbow trout. Staining of calcium-binding proteins with Quin2 is a quick and safe method, allowing the identification of calcium-binding proteins in fish semen.

Optimalisation of species identification of common carp (Cyprinus carpio) using SYBR® green I real-time PCRmethod

European Union Member States, together with a number of countries around the world, places great emphasis on ensuring the protection of consumers as a potential food allergic from food allergies. to inform consumers that their product may contain any of the risk of allergenic ingredients. For species identification of fish and fish products as a potential food allergens are used by many analytical methods as well as their authentication. We are in our work applied the method of SYBR® Green I. Real-Time PCR. We focused on pre-designed molecular - genetic marker of common carp (Cyprinus carpio), which comes from the mtDNA control D - loop area. We analyzed its presence in DNA isolates from the 5 kinds of freshwater fish, diluted to 10 % concentration. Results of using the optimized SYBR ® Green I Real-Time PCR method for species identification common carp (Cyprinus carpio) indicate to its suitability.

Seminal plasma biochemistry and spermatozoa characteristics of Atlantic cod (Gadus morhua L.) of wild and cultivated origin

Our objectives were to compare spermatozoa activity, morphology, and seminal plasma (SP) biochemistry between wild and cultivated Atlantic cod (Gadus morhua). Swimming velocities of wild cod spermatozoa were significantly faster than those of cultivated males. Wild males had a significantly larger spermatozoa head area, perimeter, and length, while cultivated males had more circular heads. Total monounsaturated fatty acids and the ratio of n-3/n-6 were significantly higher in sperm from wild males, while total n-6 from cultivated males was significantly higher than the wild males. Significantly higher concentrations of the fatty acids C14:0, C16:1n-7, C18:4n-3, C20:1n-11, C20:1n-9, C20:4n-3, C22:1n-11, and C22:6n-3 were observed in wild males, while significantly higher concentrations of C18:2n-6, C20:2n-6, and C22:5n-3 occurred in cultivated males. Osmolality, protein concentration, lactate dehydrogenase and superoxide dismutase activity of SP of wild males were significantly higher than the cultivated males. Antioxidant capacity of SP was significantly higher in cultivated males, while pH and anti-trypsin did not differ between fish origins. Four bands of anti-trypsin activity and nine protein bands were detected in SP. Performing a discriminant function analysis, on morphology and fatty acid data showed significant discrimination between wild and cultivated fish. Results are relevant to breeding programs and aquaculture development.