iTRAQ-based quantitative proteomic analysis of Macrobrachium rosenbergii hemocytes during Spiroplasma eriocheiris infection

Quantification of proteomic profile changes in the hemolymph of crayfish during in vitro coagulation

Hemolymph is the circulatory fluid that fills the body cavity of crustaceans, analogous to blood in vertebrates. Hemolymph coagulation, similar to blood clotting in vertebrates, plays a crucial role in wound healing and innate immune responses. Despite extensive studies on the clotting process in crustaceans, no comparative quantitative analysis of the protein composition of non-clotted and clotted hemolymph in any decapod has been reported. In this study, we used label-free protein quantification with high-resolution mass spectrometry to identify the proteomic profile of hemolymph in crayfish and quantify significant changes in protein abundances between non-clotted and clotted hemolymph. Our analysis identified a total of two-hundred and nineteen proteins in both hemolymph groups. Furthermore, we discussed the potential functions of the top most high and low-abundant proteins in hemolymph proteomic profile. The quantity of most of the proteins was not significantly changed during coagulation between non-clotted and clotted hemolymph, which may indicate that clotting proteins are likely pre-synthesized, allowing for a swift coagulation response to injury. Four proteins still showed abundance differences (p < 0.05, fold change>2), including C-type lectin domain-containing proteins, Laminin A chain, Tropomyosin, and Reverse transcriptase domain-containing proteins. While the first three proteins were down-regulated, the last one was up-regulated. The down-regulation of structural and cytoskeletal proteins may affect the process of hemocyte degranulation needed for coagulation, while the up-regulation of an immune-related protein might be attributed to the phagocytosis ability of viable hemocytes during coagulation.

Proteomics of the haemolymph of the terrestrial crustacean Porcellio scaber reveals components of its innate immunity under baseline conditions

The terrestrial crustacean Porcellio scaber is an established test organism in environmental research. We analysed the haemolymph proteome of P. scaber using a classical proteomic approach based on one-dimensional gel electrophoresis and tandem mass spectrometry. Using a publicly available protein database and our P. scaber transcriptome data, we have identified 76 proteins involved in cytoskeleton formation, protein degradation, vesicular transport, genetic information processing, detoxification, carbohydrate and lipid metabolism reflecting haemocyte metabolic activity, active intracellular transport, and intercellular communication. Compared with the data reported for other crustaceans, 28 of these P. scaber proteins have been linked to its immunity, among them hemocyanin, α-2-macroglobulin, phenoloxidase 3, superoxide dismutase, glutathione S-transferase, haemolymph clottable protein, and histones H4 and H2B. Our results thus provide a firm base for studying the innate immune response of P. scaber at the level of the haemolymph proteome. This knowledge is of particular importance in ecotoxicity studies with various environmental stressors where understanding physiological changes is important to reveal possible modes of action.

Molecular characterization of Rab7 and its involvement in innate immunity in red swamp crayfish Procambarus clarkii

Rab7 is a member of the Rab GTPases protein family, and it plays an essential role in regulating trafficking organelles in higher animals. However, recent studies showed that it also participated in the immune response and cytophagy against pathogens in invertebrates. In the present study, the full-length of Rab7 from Procambarus clarkii (PcRab7) was cloned, and its function during pathogen infection and phagocytosis of haemocytes was also explored. The results showed that the full-length of PcRab7 was 3639 bp, containing a 618 bp open reading frame encoding 155 amino acids. The predicted molecular weight and isoelectric point of PcRab7 were 23.2 kDa and 5.77, respectively. PcRab7 was widely expressed in various tissues including haemocytes, intestine, muscle, gill, and hepatopancreas, and the highest expression level was in haemocytes. The mRNA transcripts of PcRab7 in the main organs (gill, intestine, and hepatopancreas, and haemocytes) were significantly affected by white spot syndrome virus (WSSV) and Aeromonas veronii infection. Subsequently, the prokaryotic and eukaryotic expression vectors were successfully constructed, and polyclonal antibodies, which could specifically recognize the endogenous Rab7 protein, were also obtained. Furthermore, the phagocytosis rate of haemocytes against FITC-labeled A. veronii was significantly decreased when the PcRab7 was silenced, while the over-expression of Rab7 increased the phagocytosis rate of haemocytes. The abnormal expression of Rab7 protein could also affect the survival rate of P. clarkii infected with WSSV or A. veronii. These results could provide a basis for further study on the immunological function of PcRab7.

Comparative Proteomics Reveals the Difference in Root Cold Resistance between Vitis. riparia × V. labrusca and Cabernet Sauvignon in Response to Freezing Temperature

Grapevines, bearing fruit containing large amounts of bioactive metabolites that offer health benefits, are widely cultivated around the world. However, the cold damage incurred when grown outside in extremely low temperatures during the overwintering stage limits the expansion of production. Although the morphological, biochemical, and molecular levels in different Vitis species exposed to different temperatures have been investigated, differential expression of proteins in roots is still limited. Here, the roots of cold-resistant (Vitis. riparia × V. labrusca, T1) and cold-sensitive varieties (Cabernet Sauvignon, T3) at -4 °C, and also at -15 °C for the former (T2), were measured by iTRAQ-based proteomic analysis. Expression levels of genes encoding candidate proteins were validated by qRT-PCR, and the root activities during different treatments were determined using a triphenyl tetrazolium chloride method. The results show that the root activity of the cold-resistant variety was greater than that of the cold-sensitive variety, and it declined with the decrease in temperature. A total of 25 proteins were differentially co-expressed in T2 vs. T1 and T1 vs. T3, and these proteins were involved in stress response, bio-signaling, metabolism, energy, and translation. The relative expression levels of the 13 selected genes were consistent with their fold-change values of proteins. The signature translation patterns for the roots during spatio-temporal treatments of different varieties at different temperatures provide insight into the differential mechanisms of cold resistance of grapevine.

Early Changes in Crayfish Hemocyte Proteins after Injection with a β-1,3-glucan, Compared to Saline Injected and Naive Animals

Early changes in hemocyte proteins in freshwater crayfish Pacifastacus leniusculus, in response to an injection with the fungal pattern recognition protein β-1,3-glucan (laminarin) were investigated, as well as changes after saline (vehicle) injection and in naïve animals. Injection of saline resulted in rapid recruitment of granular hemocytes from surrounding tissues, whereas laminarin injection on the other hand induced an initial dramatic drop of hemocytes. At six hours after injection, the hemocyte populations therefore were of different composition. The results show that mature granular hemocytes increase in number after saline injection as indicated by the high abundance of proteins present in granular cell vesicles, such as a vitelline membrane outer layer protein 1 homolog, mannose-binding lectin, masquerade, crustin 1 and serine protease homolog 1. After injection with the β-1,3-glucan, only three proteins were enhanced in expression, in comparison with saline-injected animals and uninjected controls. All of them may be associated with immune responses, such as a new and previously undescribed Kazal proteinase inhibitor. One interesting observation was that the clotting protein was increased dramatically in most of the animals injected with laminarin. The number of significantly affected proteins was very few after a laminarin injection when compared to uninjected and saline-injected crayfish. This finding may demonstrate some problematic issues with gene and protein expression studies from other crustaceans receiving injections with pathogens or pattern recognition proteins. If no uninjected controls are included and no information about hemocyte count (total or differential) is given, expressions data for proteins or mRNAs are very difficult to properly interpret.

Proteomic analysis of individual giant freshwater prawn, Macrobrachium rosenbergii, growth retardants

"Iron prawn" is a condition of severe growth retardation that fishers call. The giant river prawn (Macrobrachium rosenbergii) is a commercially important species contains high protein content and functional nutrients. However, no proteomic information is available for this species. We performed the shotgun 2DLC-MS/MS proteomic analysis of the total protein from "iron prawn". Total 19,758 peptides corresponding to 2613 high-confidence proteins were identified. These proteins range in size from 40 to 70 kDa. KEGG analysis revealed that the largest group consisting total 102 KEGG pathway proteins comparing the "iron prawn" with the normal prawn. Additionally, 7, 11, 1, 6, and 5 commercially important enzymes were found in the eyestalk, liver, muscle, ovary, and testis, respectively. The functions of these differently expressed enzymes include immune system action against pathogens, muscle contraction, digestive system metabolism, cell differentiation, migration, and apoptosis in the severe growth retardation of "iron prawn". Our work provides insight into the understanding of the formation mechanism of "iron prawn".

Skin proteome profiling of tongue sole (Cynoglossus semilaevis) challenged with Vibrio vulnificus

Vibrio vulnificus is a major pathogen of cultured Cynoglossus semilaevis and results in skin ulceration and haemorrhage, but the proteomic mechanism of skin immunity against V. vulnificus remains unclear. In this study, we investigated the histopathology and skin immune response in C. semilaevis with V. vulnificus infection at the protein levels, the differential proteomic profiling of its skin was examined by using iTRAQ and LC-MS/MS analyses. A total of 951 proteins were identified in skin, in which 134 and 102 DEPs were screened at 12 and 36 hpi, respectively. Selected eleven immune-related DEPs (pvβ, Hsp71, MLC1, F2, α2ML, HCII, C3, C5, C8β, C9 and CD59) were verified for their immune roles in the V. vulnificus infection via using qRT-PCR assay. KEGG enrichment analysis revealed that most of the identified immune proteins were significantly associated with complement and coagulation cascades, antigen processing and presentation, salivary secretion and phagosome pathways. To our knowledge, this study is the first to describe the proteome response of C. semilaevis skin against V. vulnificus infection. The outcome of this study contributed to provide a new perspective for understanding the molecular mechanism of local skin mucosal immunity, and facilitating the development of novel mucosal vaccination strategies in fish.

Differentially proteomic analysis of the hemocytes against Aeromonas hydrophila infection in oriental river prawn Macrobrachium nipponense by iTRAQ approach

As the direct executors of biological function, the expression level of proteins in host will reveal the molecular mechanisms regulating bacteria infection more directly. In the present study, the differential proteomes of Macrobrachium nipponense hemocytes response to Aeromonas hydrophila infection were identified with isobaric tags for relative and absolute quantitation (iTRAQ) labeling followed by liquid chromatography electrospray ionization tandem mass spectrometry. The hemocyte proteins from the unchallenged and A. hydrophila challenged prawn, M. nipponense, at 12, 24 and 36 h post infection were compared. From this, a total of 3372 proteins were identified and 1014 proteins were considered differentially expressed, of which 117 common differentially expressed proteins were indicated between the time points. Hierarchical clustering, Gene Ontology, Kyoto Encyclopedia of Genes and Genomes enrichment and protein-protein interaction network analyses were performed for the general characterization of overall enriched proteins. Cytoskeletal proteins including myosin heavy chain, myosin regulatory light chain, actin, tubulin alpha/beta chain, troponin I and troponin T as well as antioxidant enzymes such as catalase and cytosolic MnSOD were found significantly up-regulated in hemocytes, indicating that the phagocytosis process and ROS system were induced after challenge with A. hydrophila. And other proteins such as integrin β, innexin inx2-like and heat shock protein 60 also participate in prawn immune response against bacteria. Parallel reaction monitoring analyses were carried out for validation of the expression levels of differentially expressed proteins, which indicated high reliability of the proteomic results. This is the first report on proteome of M. nipponense hemocytes against A. hydrophila infection, which contributes to better understanding on the molecular mechanisms of prawns.

iTRAQ-based proteomic analysis of the hepatopancreas from Litopenaeus vannamei after trans-vp28 gene Synechocystis sp. PCC6803 immunization

Litopenaeus vannamei (Pacific white shrimp) is one of the most commercially important varieties of shrimp cultivated in the world. Shrimp farming is a high-risk, capital-intensive industry that is susceptible to periodic outbreaks of diseases caused by viral and bacterial pathogens. Thus, there is a need to develop economically viable methods of disease control. The hepatopancreas of crustaceans are known to have an important role in their innate immune response. In this study, we have explored the immune response of the hepatopancreas from L. vannamei fed with trans-vp28 gene Synechocystis sp. PCC6803 using iTRAQ-based proteomics. A total of 214 differentially expressed proteins (DEPs) were identified, of which 143 were up-regulated and 71 were down-regulated. These proteins have diverse roles in the cell cytoskeleton and cell phagocytosis, antioxidant defense process and the response of immune related proteins. Among these proteins, the immunity associated with the functional annotation of L. vannamei was further analysed. In addition, 4 DEPs (act1, N/A, H and C7M84_013542) were analysed using parallel reaction monitoring (PRM). This is the first report of proteomics in the hepatopancreas of L. vannamei immunized with trans-vp28 gene Synechocystis sp. PCC6803.

TMT-based quantitative proteomic analysis of Eriocheir sinensis hemocytes and thoracic ganglion during Spiroplasma eriocheiris infection

Spiroplasma eriocheiris, a novel pathogen of Chinese mitten crab Eriocheir sinensis tremor disease, has led into catastrophic economic losses in aquaculture. S. eriocheiris invaded the hemocytes in the early stage, then invaded nerve tissue and caused typically paroxysmal tremors of pereiopod in the late stage of infection. The purpose of this study was to detect the infection mechanism of hemocytes in the early stage and thoracic ganglion in the late stage of S. eriocheiris infection at the protein level. Hemocytes and thoracic ganglion were collected at 24 h and 10 d after injection (the crabs with typical paroxysmal tremors of the pereiopod), respectively. TMT was performed with isobaric markers, followed by liquid chromatography tandem mass spectrometry (LC-MS/MS). In hemocytes, 127 proteins were up-regulated and 85 proteins were down-regulated in 2747 quantified proteins. Many proteins and process including proPO system proteins, hemolymph coagulation system proteins and lectins were differently expressed in hemocytes and involved in the early immune process of E. sinensis against S. eriocheiris infection. Meanwhile, 545 significantly different expression proteins (292 down-regulated and 253 up-regulated protein including a number of immune-associated, nervous system development and signal transmission related proteins) were identified in thoracic ganglion in the late stage of S. eriocheiris infection. The qRT-PCR analysis results shown that the selected significantly changed proteins in hemocytes and thoracic ganglion were consistent with the TMT proteomics. This paper reported for the first time to study the responses of crab hemocyte and thoracic ganglion against the S. eriocheiris infection at different stages. These findings help us understand the infection mechanism of S. eriocheiris at different stage with the different tissue.

iTRAQ-based mitochondrial proteome analysis of the molecular mechanisms underlying postharvest senescence of Zizania latifolia

To explore the molecular mechanisms underlying postharvest senescence of Zizania latifolia, the changes in the mitochondrial proteome of plants treated with or without (control) 1-methyleyelopropene and ethylene during storage at room temperature for 0, 3 and 6 days were investigated using isobaric tags for relative and absolute quantitation (iTRAQ) labeling combined with two-dimensional liquid chromatography-tandem mass spectrometry. A total of 1,390 proteins with two or more peptides were identified, of which 211 showed a significant (p < .05) change (at least twofold) in relative abundance. Monitoring the parallel reaction validated the reliability and accuracy of the iTRAQ results. Bioinformatics and functional analysis of these differentially expressed proteins (DEPs) revealed that postharvest senescence of Z. latifolia could be attributed to (a) strengthened pentose phosphate pathway, (b) imbalanced protein, amino acid, organic acid, and fatty acid metabolism, (c) disordered energy homeostasis, (d) exacerbated oxidative damage, (e) RNA degradation, (f) activation of the Ca²⁺ , mitogen-activated protein kinase, and jasmonic acid signaling pathways, (g) programed cell death, (h) excessive biosynthesis of secondary metabolites, or (i) degradation of cell structure. Our findings provide integrated insight into the molecular mechanisms of postharvest senescence during storage as well as the DEPs that show promise as targets for controlling senescence-induced quality deterioration of Z. latifolia. PRACTICAL APPLICATIONS: Postharvest senescence is the most important factor that causes fast quality deterioration of Zizania latifolia. The understanding of the processes leading to postharvest senescence of Z. latifolia is essential in enhancing the commercial value and extending the shelf life of the product. It is currently believed that the mitochondrial metabolism is closely related to postharvest senescence. For this, the changes of proteome in Z. latifolia mitochondria treated with or without (control) 1-MCP and ETH during storage at room temperature were investigated. Results showed that a variety of physiobiochemical responses occur during postharvest senescence of Z. latifolia. 1-MCP treatment significantly inhibited the changes of these physiobiochemical processes, finally, retarding the postharvest senescence of Z. latifolia. ETH treatment had opposite effects on proteome changes compared with 1-MCP treatment. Taken together, these results enrich the understanding of the molecular mechanisms of postharvest senescence of Z. latifolia.

Spiroplasma eriocheiris Invasion Into Macrobrachium rosenbergii Hemocytes Is Mediated by Pathogen Enolase and Host Lipopolysaccharide and β-1, 3-Glucan Binding Protein

Spiroplasma eriocheiris is a crustacean pathogen, without a cell wall, that causes enormous economic loss. Macrobrachium rosenbergii hemocytes are the major targets during S. eriocheiris infection. As wall-less bacteria, S. eriocheiris, its membrane protein should interact with host membrane protein directly and firstly when invaded in host cell. In this investigation, six potential hemocyte receptor proteins were identified firstly that mediate interaction between S. eriocheiris and M. rosenbergii. Among these proteins, lipopolysaccharide and β-1, 3-glucan binding protein (MrLGBP) demonstrated to bind to S. eriocheiris using bacterial binding assays and confocal microscopy. Four spiroplasma ligand proteins for MrLGBP were isolated and identified. But, competitive assessment demonstrated that only enolase of S. eriocheiris (SeEnolase) could be a candidate ligand for MrLGBP. Subsequently, the interaction between MrLGBP and SeEnolase was confirmed by co-immunoprecipitation and co-localization in vitro. After the interaction between MrLGBP and SeEnolase was inhibited by antibody neutralization test, the virulence ability of S. eriocheiris was effectively reduced. The quantity of S. eriocheiris decreased in Drosophila S2 cells after overexpression of MrLGBP, compared with the controls. In addition, RNA interference (RNAi) knockdown of MrLGBP made M. rosenbergii more sensitive to S. eriocheiris infection. Further studies found that the immune genes, including MrLGBP and prophenoloxidase (MrproPO), MrRab7A, and Mrintegrin α1 were significantly up-regulated by SeEnolase stimulation. After SeEnolase pre-stimulation, the ability of M. rosenbergii resistance to S. eriocheiris was significantly improved. Collectively, this investigation demonstrated that MrLGBP and pathogen SeEnolase involved in mediating S. eriocheiris invasion into M. rosenbergii hemocytes.

Integrated Analysis of Transcriptomic, miRNA and Proteomic Changes of a Novel Hybrid Yellow Catfish Uncovers Key Roles for miRNAs in Heterosis

Heterosis is a complex biological phenomenon in which hybridization produces offspring that exhibit superior phenotypic characteristics compared with the parents. Heterosis is widely utilized in agriculture, for example in fish farming; however, its underlying molecular basis remains elusive. To gain a comprehensive and unbiased molecular understanding of fish heterosis, we analyzed the mRNA, miRNA, and proteomes of the livers of three catfish species, Pelteobagrus fulvidraco, P. vachelli, and their hybrid, the hybrid yellow catfish "Huangyou-1" (P. fulvidraco ♀ × P. vachelli ♂). Using next-generation sequencing and mass spectrometry, we show that the nonadditive, homoeolog expression bias and expression level dominance pattern were readily identified at the transcriptional, post-transcriptional, or protein levels, providing the evidence for the widespread presence of dominant models during hybridization. A number of predicted miRNA-mRNA-protein pairs were found and validated by qRT-PCR and PRM assays. Furthermore, several diverse key pathways were identified, including immune defense, metabolism, digestion and absorption, and cell proliferation and development, suggesting the vital mechanisms involved in the generation of the heterosis phenotype in progenies. We propose that the high parental expression of genes/proteins (growth, nutrition, feeding, and disease resistance) coupled with low parental miRNAs of the offspring, are inherited from the mother or father, thus indicating that the offspring were enriched with the advantages of the father or mother. We provide new and important information about the molecular mechanisms of heterosis, which represents a significant step toward a more complete elucidation of this phenomenon.

iTRAQ-Based Quantitative Proteomic Profiling of Staphylococcus aureus Under Different Osmotic Stress Conditions

Staphylococcus aureus (S. aureus) is an extremely halotolerant pathogenic bacterium with high osmotic stress tolerance, and it is frequently encountered in aquatic production and preservation. However, the mechanism underlying the extremely high osmotic stress tolerance of S. aureus remains unclear. In this study, the isobaric tags for relative and absolute quantification (iTRAQ) method was used to identify the differentially expressed proteins (DEPs) under different sodium chloride (NaCl) concentrations. Compared with the control group (0% NaCl), the 10 and 20% NaCl groups had 484 DEPs and 750 DEPs, respectively. Compared with the 10% NaCl group, the 20% NaCl group had 361 DEPs. Among the DEPs, proteins involved in fatty acid synthesis, proline/glycine betaine biosynthesis and transportation, stress tolerance, cell wall biosynthesis and the TCA cycle were upregulated, whereas proteins associated with biofilm formation and pathogenic infections were downregulated. The results obtained in this study indicate that under extremely high osmotic stress, modification of the cell membrane structure, increased biosynthesis and transportation of osmotic protectants, and redistribution of energy metabolism contribute to the osmotic stress tolerance of S. aureus, and the infectious ability of the bacteria may be limited. The aim of this study was to provide new insight into how S. aureus tolerates the high-salt conditions involved in aquatic production and preservation.

Proteomic and metabolomic responses in hepatopancreas of whiteleg shrimp Litopenaeus vannamei infected by microsporidian Enterocytozoon hepatopenaei

Enterocytozoon hepatopenaei (EHP) causes hepatopancreatic microsporidiosis (HPM) in shrimp. HPM is not normally associated with shrimp mortality, but is associated with significant growth retardation. In this study, the responses induced by EHP were investigated in hepatopancreas of shrimp Litopenaeus vannamei using proteomics and metabolomics. Among differential proteins identified, several (e.g., peritrophin-44-like protein, alpha2 macroglobulin isoform 2, prophenoloxidase-activating enzymes, ferritin, Rab11A and cathepsin C) were related to pathogen infection and host immunity. Other proteomic biomarkers (i.e., farnesoic acid o-methyltransferase, juvenile hormone esterase-like carboxylesterase 1 and ecdysteroid-regulated protein) resulted in a growth hormone disorder that prevented the shrimp from molting. Both proteomic KEGG pathway (e.g., "Glycolysis/gluconeogenesis" and "Glyoxylate and dicarboxylate metabolism") and metabolomic KEGG pathway (e.g., "Galactose metabolism" and "Biosynthesis of unsaturated fatty acids") data indicated that energy metabolism pathway was down-regulated in the hepatopancreas when infected by EHP. More importantly, the changes of hormone regulation and energy metabolism could provide much-needed insight into the underlying mechanisms of stunted growth in shrimp after EHP infection. Altogether, this study demonstrated that proteomics and metabolomics could provide an insightful view into the effects of microsporidial infection in the shrimp L. vannamei.

Proteomic analysis of the potential mechanism of fading of aroma-related esters in "Nanguo" pears after long-term refrigeration

Low-temperature storage is a key method for delaying the ripening of "Nanguo" pears. However, the aroma of "Nanguo" pears fades after long-term refrigeration. We investigated the potential mechanism of fading of aroma in "Nanguo" pears by analyzing differentially expressed proteins in pears stored at room temperature, which had higher level of aromatic esters and those stored at low temperature, having lower esters. We observed that 293 kinds of proteins were down-regulated and 377 were up-regulated. Gene ontology analysis showed that proteins in the "catalytic activity," "metabolic process," "organelle," and "membrane" proteins were affected by low temperature. KEGG analysis showed that the differentially expressed proteins were involved in oxidative phosphorylation, carbon and fatty acid metabolism. Real-time PCR showed that transcription levels of nine selected genes correlated with differentially expressed proteins. The results revealed that the expression of potentially aroma-related proteins, which are important in further research on improving aroma quality of "Nanguo" pears. PRACTICAL APPLICATIONS: "Nanguo" pears aroma is an important character for attracting consumers and many proteins are involved in the synthesis of aroma. However, their aroma is lost after cold storage and the quality of fruits is affected by low temperature. It is, therefore, of great significance to study the potential proteins that regulate the aroma of refrigerated "Nanguo" pears. In addition, the study results could provide basic and scientific data for the study of improving the aroma quality and genetic improvement of "Nanguo" pears.

The structural and proteomic analysis of Spiroplasma eriocheiris in response to colchicine

Spiroplasma eriocheiris, a pathogen that causes mass mortality of Chinese mitten crab Eriocheir sinensis, is a wall less bacteria and belongs to the Mollicutes. This study was designed to investigate the effects of colchicine on S. eriocheiris growth, cell morphology, and proteins expression. We found that in the presence of colchicine, the spiroplasma cells lost their helicity, and the length of the cells in the experimental group was longer than that of the control. With varying concentrations of the colchicine treatment, the total time to achieve a stationary phase of the spiroplasma was increased, and the cell population was decreased. The virulence ability of S. eriocheiris to E. sinensis was effectively reduced in the presence of colchicine. To expound the toxical mechanism of colchicine on S. eriocheiris, 208 differentially expressed proteins of S. eriocheiris were reliably quantified by iTRAQ analysis, including 77 up-regulated proteins and 131 down-regulated proteins. Especially, FtsY, putative Spiralin, and NADH oxidase were down-regulated. F₀F₁ ATP synthase subunit delta, ParB, DNABs, and NAD(FAD)-dependent dehydrogenase were up-regulated. A qRT-PCR was conducted to detect 7 expressed genes from the iTRAQ results during the incubation. The qRT-PCR results were consistent with the iTRAQ results. All of our results indicate that colchicine have a strong impact on the cell morphology and cellular metabolism of S. eriocheiris.

iTRAQ-based quantitative proteomic analysis of Procambarus clakii hemocytes during Spiroplasma eriocheiris infection

As a new-found aquaculture pathogen, Spiroplasma eriocheiris, has resulted in inconceivable economic losses in aquaculture. In the infection of S. eriocheiris, the Procambarus clakii hemocytes have indicated to be major target cells. What was designed to examine in our study is the hemocytes' immune response at the protein levels. Before the pathogen was injected and after 192 h of post-injection, the differential proteomes of the crayfish hemocytes were analyzed immediately by isobaric tags for relative and absolute quantization (iTRAQ) labeling, followed by liquid chromatogramphytandem mass spectrometry (LC-MS/MS). This research had identified a total of 285 differentially expressed proteins. Eighty-three and 202 proteins were up-regulated and down-regulated, respectively, caused by the S. eriocheiris infection. Up-regulated proteins included alpha-2-macroglobulin (α2M), vitellogenin, ferritin, etc. Down-regulated proteins, involved with serine protease, peroxiredoxin 6, 14-3-3-like protein, C-type lectin, cdc42 homolog precursor, etc. The prophenoloxidase-activating system, antimicrobial action involved in the immune responses of P. clarkii is considered to be damaged due to S. eriocheiris infection. The present work could lay the foundation for future research on the proteins related to the susceptibility/resistance of P. clarkii to S. eriocheiris. In addition, it is helpful for our understanding molecular mechanism of disease processes in crayfishes.

The function of serpin-2 from Eriocheir sinensis in Spiroplasma eriocheiris infection

Serpin families classified serine protease inhibitors regulate various physiological processes. However, there is not study on the role of serpin in immune responses against Spiroplasma eriocheiris as a novel causative pathogen in the Chinese mitten crab, Eriocheir sinensis. In our study, quantitative real-time PCR (qRT-PCR) revealed that the mRNA transcripts of Esserpin-2 were ubiquitous in every tissue, relative higher expression in hepatopancreas, gill and hemocytes, while the intestine, muscle, heart and nerve showed relative lower expression. Followed by infection with S. eriocheiris, the transcripts of Esserpin-2 were significantly down-regulated from 1 d to 7 d. After double-stranded RNA injection, the transcripts of Esserpin-2 dramatically declined from 48 h to 96 h. The transcripts of proPO were found to be obviously increased after Esserpin-2 silenced, meanwhile, LGBP with no significant difference. The copy number of S. eriocheiris and subsequently the mortality of crabs in a silencing Esserpin-2 group were significantly less than control groups during infection. The subcellular localization experiment suggested that recombinant Esserpin-2 was mainly located in the cytoplasm. Finally, over-expression assay in Drosophila S2 cells indicated that Esserpin-2 could increase copies of S. eriocheiris and result in cell death. These findings demonstrated that Esserpin-2 involved in the innate immune mechanism of E. sinensis in response to S. eriocheiris infection.

Proteomic analysis of peel browning of 'Nanguo' pears after low-temperature storage

BACKGROUND

Postharvest ripening of the 'Nanguo' pear (Pyrus ussuriensis Maxim.) can be impeded by low-temperature storage. However, pears after long-term refrigeration are prone to peel browning when returned to room temperature conditions. This study investigated the browning mechanism of 'Nanguo' pear stored at a low temperature by analysing the differentially expressed proteins between healthy fruit and fruit with peel browning.

RESULTS

The results showed that 181 proteins underwent statistically significant changes. A categorisation of the disparately accumulated proteins was performed using gene ontology annotation. The results showed that the 'metabolic process', 'cellular process', 'catalytic activity', and 'binding' proteins were the most affected after low-temperature storage. Further analysis revealed that the differentially expressed proteins, which are related to peel browning, are primarily involved in the phenylpropanoid pathway, linoleic acid pathways, fatty acid biosynthesis pathway, glutathione metabolism pathway, photosynthesis pathway, oxidative phosphorylation pathway, and glycolysis pathway.

CONCLUSION

This study reveals that there are variations in key proteins in 'Nanguo' pear after low-temperature storage, and the identification of these proteins will be valuable in future functional genomics studies, as well as provide protein resources that can be used in the efforts to improve pear quality. © 2016 Society of Chemical Industry.