Invasion of Ceratomyxa shasta (Myxozoa) and comparison of migration to the intestine between susceptible and resistant fish hosts

The myxozoan parasite Ceratomyxa shasta infects salmonids causing ceratomyxosis, a disease elicited by proliferation of the parasite in the intestine. This parasite is endemic to the Pacific Northwest of North America and salmon and trout strains from endemic river basins show increased resistance to the parasite. It has been suggested that these resistant fish (i) exclude the parasite at the site of invasion and/or (ii) prevent establishment in the intestine. Using parasites pre-labeled with a fluorescent stain, carboxyfluorescein succinimidyl diacetate (CFSE), the gills were identified as the site of attachment of C. shasta in a susceptible fish strain. In situ hybridization (ISH) of histological sections was then used to describe the invasion of the parasites in the gill filaments. To investigate differences in the progress of infection between resistant and susceptible fish, a C. shasta-susceptible strain of rainbow trout (Oncorhynchus mykiss) and a C. shasta-resistant strain of Chinook salmon (Oncorhynchus tshawytscha) were sampled at consecutive time points following exposure at an endemic site. Using ISH in both species, the parasite was observed to migrate from the gill epithelium into the gill blood vessels where replication and release of parasite stages occurred. Quantitative PCR verified entry of the parasite into the blood. Parasite levels in blood increased 4 days p.i. and remained at a consistent level until the second week when parasite abundance increased further and coincided with host mortality. The timing of parasite replication and migration to the intestine were similar for both fish species. The field exposure dose was unexpectedly high and apparently overwhelmed the Chinook salmon’s defenses, as no evidence of resistance to parasite penetration into the gills or prevention of parasite establishment in the intestine was observed.     

Genomic heritability estimation for the early life‐history transition related to propensity to migrate in wild rainbow and steelhead trout populations

A previous genomewide association study (GWAS) identified SNP markers associated with propensity to migrate of rainbow and steelhead trout (Oncorhynchus mykiss) in a connected population with free access to the ocean in Upper Yakima River (UYR) and a population in Upper Mann Creek (UMC) that has been sequestered from its access to the ocean for more than 50 years. Applying genomic heritability estimation using the same dataset, we found that smoltification in the UYR population were almost completely determined by additive effects, with 95.5% additive heritability and 4.5% dominance heritability, whereas smoltification in the UMC population had substantial dominance effects, with 0% additive heritability and 39.3% dominance heritability. Dominance test detected one SNP marker ({"type":"entrez-nucleotide","attrs":{"text":"R30393","term_id":"937054","term_text":"R30393"}}R30393) with significant dominance effect on smoltification (P = 1.98 × 10⁻⁷). Genomic-predicted additive effects completely separated migratory and nonmigratory fish in the UYR population, whereas genomic-predicted dominance effects achieved such complete separation in the UMC population. The UMC population had higher genomic additive and dominance correlations than the UYR population, and fish between these two populations had the least genomic correlations. These results suggested that blocking the free access to the ocean may have reduced genetic diversity and increased genomic similarity associated with the early life-history transition related to propensity to migrate.     

A putative serine protease,SpSsp1, from Saprolegnia parasitica is recognised by sera of rainbow trout, Oncorhynchus mykiss

Saprolegniosis, the disease caused by Saprolegnia sp., results in considerable economic losses in aquaculture. Current control methods are inadequate, as they are either largely ineffective or present environmental and fish health concerns. Vaccination of fish presents an attractive alternative to these control methods. Therefore we set out to identify suitable antigens that could help generate a fish vaccine against Saprolegnia parasitica. Unexpectedly, antibodies against S. parasitica were found in serum from healthy rainbow trout, Oncorhynchus mykiss. The antibodies detected a single band in secreted proteins that were run on a one-dimensional SDS-polyacrylamide gel, which corresponded to two protein spots on a two-dimensional gel. The proteins were analysed by liquid chromatography tandem mass spectrometry. Mascot and bioinformatic analysis resulted in the identification of a single secreted protein, SpSsp1, of 481 amino acid residues, containing a subtilisin domain. Expression analysis demonstrated that SpSsp1 is highly expressed in all tested mycelial stages of S. parasitica. Investigation of other non-infected trout from several fish farms in the United Kingdom showed similar activity in their sera towards SpSsp1. Several fish that had no visible saprolegniosis showed an antibody response towards SpSsp1 suggesting that SpSsp1 might be a useful candidate for future vaccination trial experiments.     

Eleven polymorphic microsatellite loci for the salmonid trematode Plagioporus shawi

We isolated and characterized 11 microsatellite loci from Plagioporus shawi, a parasitic trematode of salmonid fishes (Oncorhynchus spp.). Extensive polymorphism (expected heterozygosities ranging from 0.476 to 0.981 and number of alleles from 10 to 55) was found in a sample of 94 trematodes from 24 infected cutthroat trout (Oncorhynchus clarki) individuals. Nine of the 11 loci will be useful for future genetic studies on within population dynamics of P. shawi.     

Mating systems and predictors of relative reproductive success in a Cutthroat Trout subspecies of conservation concern

Mating systems and patterns of reproductive success in fishes play an important role in ecology and evolution. While information on the reproductive ecology of many anadromous salmonids (Oncorhynchus spp.) is well detailed, there is less information for nonanadromous species including the Yellowstone Cutthroat Trout (O. clarkii bouvieri), a subspecies of recreational angling importance and conservation concern. Using data from a parentage‐based tagging study, we described the genetic mating system of a migratory population of Yellowstone Cutthroat Trout, tested for evidence of sexual selection, and identified predictors of mating and reproductive success. The standardized variance in mating success (i.e., opportunity for sexual selection) was significantly greater for males relative to females, and while the relationship between mating success and reproductive success (i.e., Bateman gradient) was significantly positive for both sexes, a greater proportion of reproductive success was explained by mating success for males (r ² = 0.80) than females (r ² = 0.59). Overall, the population displayed a polygynandrous mating system, whereby both sexes experienced variation in mating success due to multiple mating, and sexual selection was variable across sexes. Tests for evidence of sexual selection indicated the interaction between mating success and total length best‐predicted relative reproductive success. We failed to detect a signal of inbreeding avoidance among breeding adults, but the group of parents that produced progeny were on average slightly less related than adults that did not produce progeny. Lastly, we estimated the effective number of breeders (N _b) and effective population size (N _e) and identified while N _b was lower than N _e, both are sufficiently high to suggest Yellowstone Cutthroat Trout in Burns Creek represent a genetically stable and diverse population.     

Influence of immune‐relevant genotype on the reproductive success of a salmonid alternative mating strategy

Major histocompatibility complex (MHC) and immune‐relevant gene markers were used to evaluate differences in reproductive success (RS) among naturally spawning coho salmon Oncorhynchus kisutch mate pairs involving an alternative male reproductive phenotype, known as jacks. These mate pairs included both hatchery‐reared and wild origin fish such that three classes were evaluated in two consecutive years (2005 and 2006) using a previously constructed multigenerational genetic pedigree: wild × wild (W × W), hatchery × hatchery (H × H) and wild × hatchery (W × H). Oncorhynchus kisutch jack mate pairs mated randomly based on immune‐relevant genotype in both years; a result consistent with the opportunistic mating strategy of jacks. An association between greater number of alleles shared at three immune‐relevant gene markers and increased RS was found for: W × H mate pairs in 2005 (BHMS429), W × H pairs in 2006 (SsalR016TKU) and W × W pairs in 2006 (OMM3085). No correlation between immune gene diversity and RS was found for H × H pairs in either year. The results suggest that the influence of immune‐relevant genotype on mating success may be different for jacks when compared with previous studies of large adult male O. kisutch.     

Ultrastructure of the retinal pigment epithelium in the young masu salmon Oncorhynchus masou

The ultrastructure of retinal pigment epithelium (RPE) cells in the masu salmon Oncorhynchus masou fry was studied. The physiological state of the pigment was dependent on the level of light/dark adaptation. Similar morphological properties were observed in the response of the RPE cells to light and a magnetic field.     

Fatty‐Acid Profile of Total and Polar Lipids in Cultured Rainbow Trout (Oncorhynchus mykiss) Raised in Freshwater and Seawater (Croatia) Determined by Transmethylation Method

Fatty acids from total lipids and polar lipids in cultured rainbow trout (Oncorhynchus mykiss) raised in seawater (SW) and freshwater (FW) were identified and quantified from the muscle samples in January, April, and July. The highest total lipid and polar lipid amounts were found in April. July contents of total lipids were low, but percent of the polyunsaturated fatty acids (PUFAs) was high in SW and FW environment (particularly n‐3 PUFAs). Variety of 17 fatty acids was identified by GC‐FID after transmethylation. The predominant fatty acids in rainbow trout from SW and FW were: docosahexaenoic acid among n‐3 PUFAs, palmitic acid among saturated fatty acids (SFAs), and oleic acid among monounsaturated fatty acids (MUFAs). Appreciably higher n‐3/n‐6 ratio was found in total lipids in April (6.40, FW fish) and in polar lipids in July (18.76; SW fish). High n‐3/n‐6 ratio in total lipids and polar lipids of rainbow trout from SW and FW, besides beneficial n‐3/n‐6 ratio in the commercial fish food, could be characteristic for the local environmental conditions (Croatia).     

Olfactory gene expression in migrating adult sockeye salmon Oncorhynchus nerka

Expression of 12 olfactory genes was analysed in adult sockeye salmon Oncorhynchus nerka nearing spawning grounds and O. nerka that had strayed from their natal migration route. Variation was found in six of these genes, all of which were olfc olfactory receptors and had lower expression levels in salmon nearing spawning grounds. The results may reflect decreased sensitivity to natal water olfactory cues as these fish are no longer seeking the correct migratory route. The expression of olfactory genes during the olfactory‐mediated spawning migration of Pacific salmon Oncorhynchus spp. is largely unexplored and these findings demonstrate a link between migratory behaviours and olfactory plasticity that provides a basis for future molecular research on salmon homing.     

不同月龄虹鳟肝显微及超微结构特征

应用多种组织化学方法和透射电镜技术,对同一生长条件下8月龄、20月龄及30月龄虹鳟（Oncorhynchus mykiss）肝显微结构和超微结构特征进行研究。结果表明：不同月龄虹鳟肝被膜均为单层扁平上皮,厚度变化明显;肝细胞为单核,8月龄细胞排列不明显,20月龄及30月龄形成完整双层管式排列,胆管及其周围结缔组织随月龄发育尤为明显,血窦分支吻合成网状,窦壁内皮细胞扁平,胞质孔较多,窦腔内巨噬细胞具有典型胞质突,但并没有观察到Kupffer细胞;各月龄组肝星状细胞发育完善,胞突彼此相连;汇管区分为胆管孤管型、胆管动脉型、胆管静脉型、胆管动静脉型4种,8月龄以胆管孤管型为主,20月龄以胆管动脉型为主,30月龄以胆管动脉型、胆管动脉静脉型为主。因此,性成熟前虹鳟肝组织结构与其生理发育密切相关,胆管系统结构形式随月龄变化明显,肝细胞排列逐渐完善,Disse间隙胶原纤维及网状纤维含量逐渐增加,与被膜、中央静脉及汇管区结缔组织互相延伸,构成肝完整骨架,有利于调节肝细胞正常生理功能。     

A Tn7-Like Transposon Is Present in the glmUS Region of the Obligately Chemoautolithotrophic Bacterium Thiobacillus ferrooxidans

The region downstream of the Thiobacillus ferrooxidans ATCC 33020 atp operon was examined, and the genes encoding N-acetylglucosamine-1-uridyltransferase (glmU) and glucosamine synthetase (glmS) were found. This atpEFHAGDC-glmUS gene order is identical to that of Escherichia coli. The T. ferrooxidans glmS gene was shown to complement E. coli glmS mutants for growth on minimal medium lacking glucosamine. A Tn7-like transposon, Tn5468, was found inserted into the region immediately downstream of the glmS gene in a manner similar to the site-specific insertion of transposon Tn7 within the termination region of the E. coli glmS gene. Tn5468 was sequenced, and Tn7-like terminal repeat sequences as well as several open reading frames which are related to the Tn7 transposition genes tnsA, tnsB, tnsC, and tnsD were found. Tn5468 is the closest relative of Tn7 to have been characterized to date. Southern blot hybridization indicated that a similar or identical transposon was present in three T. ferrooxidans strains isolated from different parts of the world but not in two Thiobacillus thiooxidans strains or a Leptospirillum ferrooxidans strain. Since T. ferrooxidans is an obligately acidophilic autotroph and E. coli is a heterotroph, ancestors of the Tn7-like transposons must have been active in a variety of physiologically different bacteria so that their descendants are now found in bacteria that occupy very different ecological niches.     

Six diagnostic single nucleotide polymorphism markers for detecting introgression between cutthroat and rainbow trouts

Ten primer pairs were screened to develop single nucleotide polymorphism (SNP) TaqMan assays that will distinguish California golden trout and some rainbow trouts (Oncorhynchus mykiss sspp., O. m. aguabonita) from the Paiute and Lahontan cutthroat trouts (Oncorhynchus clarkii seleniris, O. c. henshawi). From these 10 primer pairs, one mitochondrial and five nuclear fixed SNP differences were discovered and developed into TaqMan assays. These six assays will be useful for characterizing and monitoring hybridization between these groups. Additional Oncorhynchus clarkii sspp. and Oncorhynchus mykiss sspp. were assayed to determine if these assays are useful in closely related species.     

What is the primary function of the early teleost gill? Evidence for Na+/NH+4 exchange in developing rainbow trout (Oncorhynchus mykiss)

Post-hatch fishes lack a functional gill and use cutaneous surfaces for exchange with the surrounding environment. The ionoregulatory hypothesis posits that ionoregulation is the first physiological process to be limited by cutaneous exchange, necessitating its shift to the gills. We hypothesized that the ontogeny of branchial ammonia excretion (J_amm) is coupled to Na⁺ uptake () in accordance with the current model for exchange in freshwater. Using divided chambers, branchial and cutaneous J_amm, and oxygen consumption (MO₂) by larval rainbow trout were assessed. Following hatch, the skin accounted for 97% and 86% of total J_amm and , respectively. J_amm and shifted to the gills simultaneously at 15 days post-hatch (dph) and were highly correlated (R² = 0.951) at the gills, but not the skin, over development. Contrastingly, MO₂ shifted significantly later at 27 dph, in agreement with the ionoregulatory hypothesis. Moreover, the mRNA expression and/or enzymatic activity of Rhesus proteins, Na⁺/H⁺-exchanger, H⁺-ATPase, Na⁺/K⁺-ATPase and carbonic anhydrase, all key components of the -exchange system, increased in the gills over larval development. We propose that the ontogeny of branchial occurs as exchange and provide evidence for a novel element to the ionoregulatory hypothesis, the excretion of potentially lethal metabolic ammonia.     

Impacts of introduced Spartina alterniflora along an elevation gradient at the Jiuduansha Shoals in the Yangtze Estuary,suburban Shanghai,China

Although much research has focused upon the negative impacts of invasive Spartina alterniflora upon salt marshes dominated by other Spartina spp., little is known about its impacts upon native Scirpus mariqueter marshes. In 1997, S. alterniflora was introduced to the Jiuduansha Shoals, Yangtze Estuary, China, to accelerate the formation of marsh habitat via accretionary processes, with the larger goal of drawing waterfowl away from wetlands near the Pudong International Airport, Shanghai, China. In 2000, a nature reserve was established on the Jiuduansha Shoals, making the impact upon the native S. mariqueter community a high priority for research. Our objective was to quantify the impacts of introduced S. alterniflora and Phragmites australis to the native S. mariqueter-dominated community at this site in four elevation zones, as compared with a nearby natural shoal. We found that species diversity was greater in the lower elevations with the engineering, through elimination of the natural dominance of S. mariqueter. We also found that diversity was lessened in the higher elevations, due to rapid growth and exclusion by the planted S. alterniflora in conjunction with the native P. australis. Moreover, we found that the growth of the native S. mariqueter was stimulated when S. alterniflora was planted nearby. It is quite likely that the net effect of these ecological processes will be to accelerate further accretion, leading to an eventual replacement of the S. mariqueter-dominated community in the long-term. Future management approaches should focus upon harvesting, grazing, and perimeter-ditching the S. alterniflora to avoid this situation.     

Novel Ree1 regulates the expression of ENO1 via the Snf1 complex pathway in Saccharomyces cerevisiae

Using cDNA microarray analysis, we found that the mRNA of YJL217W and several other genes related to cell wall organization and biogenesis were up-regulated by galactose in Saccharomyces cerevisiae early during the induction process. YJL217W is also known as REE1 (Regulation of Enolase I). Both the Gal4 regulatory region and the Mac1 binding domain were found on the upstream region of REE1, and the expression of REE1 was up-regulated by galactose but not by glucose. The up-regulation of REE1 by galactose was not observed in the Δgal4 strain. From the two-hybrid analysis, we found that Ree1 physically interacted with Gal83. Furthermore, from 2-D gel electrophoresis we found that the deletion of REE1 resulted in the up-regulation of Eno1. From Western blotting, we learned that the expression of Eno1 in the Δree1 strain was different from that in wild-type strains and that Eno1 expression was not changed by glucose stimulation. Taken together, these results suggest that Ree1p functions in the galactose metabolic pathway via the Gal83 protein and that it may control the level of Eno1p, which is also affected by the Snf1 complex, in S. cerevisiae.     

A Minisatellite Sequence within the Propeptide Region of the Vacuolar Carboxypeptidase Y Gene of Schizosaccharomyces pombe

We describe the presence of a minisatellite sequence that displays length polymorphisms in the fission yeast Schizosaccharomyces pombe. The minisatellite sequence was found to reside within the propeptide region of the vacuolar carboxypeptidase Y gene. The minisatellite sequence, which was found only at a single locus, was mitotically stable and displayed length polymorphisms between the two varieties of S. pombe (S. pombe var. pombe and S. pombe var. malidevorans). The minisatellite sequence, however, appeared to be species specific and was absent in other members of the Schizosaccharomyces genus. This report constitutes the first experimental demonstration of the presence of such sequences in yeasts.     

Autoregulation of the partition genes of the mini-F plasmid and the intracellular localization of their products in Escherichia coli

The sopAB operon and the sopC sequence, which acts as a centromere, are essential for stable maintenance of the mini-F plasmid. Immunoprecipitation experiments with purified SopA and SopB proteins have demonstrated that these proteins interact in vitro. Expression studies using the lacZ gene as a reporter revealed that the sopAB operon is repressed by the cooperative action of SopA and SopB. Using immunofluorescence microscopy, we found discrete fluorescent foci of SopA and SopB in cells that produce both SopA and SopB in the presence of the sopC DNA segment, but not in the absence of sopC, suggesting the SopA-SopB complex binds to sopC segments. SopA was exclusively found to colocalize with nucleoids in cells that produced only SopA, while, in the absence of SopA, SopB was distributed in the cytosolic spaces.     

Members of the amylovora group of Erwinia are cellulolytic and possess genes homologous to the type II secretion pathway

A cellulase-producing clone was isolated from a genomic library of the Erwinia rhapontici (Millard) Burkholder strain NCPPB2989. The corresponding gene, named celA, encodes an endoglucanase (EC?3.2.1.4) with the extremely low pH optimum of 3.4 and a temperature optimum between 40 and 50?°C. A single ORF of 999?nt was found to be responsible for the Cel activity. The corresponding protein, named CelA, showed 67% identity to the endoglucanase Y of E. chrysanthemi and 51.5% identity to the endoglucanase of Cellulomonas uda, and thus belongs to the glycosyl hydrolase family?8. The celA gene, or its homologue, was found to be present in all E. rhapontici isolates analysed, in E. chrysanthemi, and in E. amylovora. The presence of plant cell wall-degrading enzymes in the amylovora group of Erwinia spp. had not previously been established. Furthermore, the DNA of both E. rhapontici and E. amylovora was found to exhibit homology to genes encoding the type?II (GSP) secretion pathway, which is known to be responsible for extracellular targeting of cellulases and pectinases in Erwinia spp. that cause soft rotting, such as E. carotovora and E. chrysanthemi. Secretion of the CelA protein by E. rhapontici could not be verified. However, the CelA protein itself was found to include the information necessary for heterologous secretion by E. chrysanthemi.     

PLIN1 deficiency affects testicular gene expression at the meiotic stage in the first wave of spermatogenesis

PLIN1, a lipid droplet associated protein, has been implicated in playing a key role in the regulation of lipolysis and lipid storage in adipocytes. PLIN1 is found to be highly expressed in Leydig cells of testis, suggesting a potential role in steroidogenesis and spermatogenesis. In this study, we showed that PLIN1 was expressed in testis and that its mRNA levels declined significantly with development. To investigate the role of PLIN1, we take advantage of PLIN1-null mice. We found that the number of seminiferous tubules containing round spermatids was significantly increased at P21 (postnatal day 21). Furthermore, microarray analysis showed that there were 538 differentially expressed genes between PLIN1-null and wild-type mice at P21. The up-regulated genes in knockout mice were enriched in spermatogenesis by Gene Ontology classification. Among them, Prm1 and Wbp2nl are important for spermatogenesis which were confirmed by real-time PCR. Unexpectedly, the levels of serum testosterone and serum 17β-estradiol as well as steroidogenic genes are not altered in the PLIN1-null mice. Compared to the wild-type mice, no significant difference of fertility was found in the PLIN1-null mice. Therefore, these findings indicated that PLIN1 disruption leads to the increase of round spermatid-containing seminiferous tubules at the meiotic stage of the first wave of spermatogenesis through regulating spermatogenic related genes.