Fertilization (activation)-induced 200- to 9-kDa depolymerization of polysialoglycoprotein, a distinct component of cortical alveoli of rainbow trout eggs

Polysialoglycoprotein, a novel type of glycoprotein found in the eggs of rainbow trout has been shown to undergo dramatic depolymerization (200- to 9-kDa) upon fertilization of the eggs. Molecular mechanism of this depolymerization has been elucidated to be the result of proteolysis catalyzed by a highly specific protease induced at fertilization. The low molecular weight polysialoglycoprotein obtained from the fertilized eggs accounted for about 85% of total polysialoglycoprotein and comprised glycotridecapeptides with a uniform peptide sequence which was determined to be Asp-Asp-Ala-Thr*-Ser*-Glu-Ala-Ala-Thr*-Gly-Pro-Ser-Gly, where * indicates the site of glycosylation. This glycotridecapeptide constitutes a repeating unit of the 200-kDa polysialoglycoprotein in the unfertilized eggs: (Asp) 0-2-Ala-Thr*-Ser*-Glu-Ala-Ala-Thr*-Gly-Pro-Ser-Gly-(Asp-Asp-Ala-Thr*-Ser *-Glu- Ala-Ala-Thr*-Gly-Pro-Ser-Gly)n (n = 25) (Kitajima, K., Inoue, Y., and Inoue, S. (1986) J. Biol. Chem. 261, 5262-5269). The fertilization-induced depolymerization of polysialoglycoprotein appeared to be completed within 5 min postfertilization. The same reaction was also induced by parthenogenetic activation of the eggs by immersing in fresh water or nonelectrolyte solutions. Thus the phenomenon is closely associated with the exocytosis of cortical vesicles (alveoli) of the eggs.     

Molecular cloning and characterization of cDNAs coding for apo-polysialoglycoprotein of rainbow trout eggs. Multiple mRNA species transcribed from multiple genes contain diverged numbers of exact 39-base (13-amino acid) repeats

Polysialoglycoprotein (PSGP) of unfertilized eggs of rainbow trout (Salmo gairdneri) consists of tandem repeats (about 25) of a glycotridecapeptide, Asp-Asp-Ala-Thr*-Ser*-Glu-Ala-Ala-Thr*-Gly-Pro-Ser-Gly (* denotes the attachment site of a polysialoglycan chain) (Kitajima, K., Inoue, Y., and Inoue, S. (1986) J. Biol. Chem. 261, 5262-5269). By using oligodeoxynucleotide probes based on the above sequence, we isolated a genomic clone for apoPSGP which contains 39-base pair repeats (5'-GACGACGCCACCTCTGAAGCT-GCGACCGGCCCGTCTGGC-3') encoding the tridecapeptide. Using a fragment of this genomic DNA as a probe, we next screened a cDNA library constructed with mRNA from immature ovaries of rainbow trout. Nucleotide sequencing analyses of cDNA clones thus obtained revealed that apoPSGP is encoded by multiple mRNA species consisting of diverged numbers (6-32) of the 39-base repeat encoding the tridecapeptide unit and homologous 5'- and 3'-bordering regions. The encoded protein consists of three distinct regions: the N-region consisting of a putative signal peptide and a pro-peptide, the R-region containing diverged numbers of the tandem repeat of 13-amino acid residues, and the C-region with six amino acid residues. Southern blot analysis showed that multiple mRNAs are transcribed from multiple genes for apoPSGP containing diverged numbers of the 39-base pair repeat. Thus, the genes for apoPSGP constitute a multigene family. Expression of the mRNAs is stage and organ specific, i.e. they are expressed only in immature ovaries and not in mature ovaries or in any other organ.     

A comparative analysis of aggression in migratory and non-migratory salmonids

This paper represents a comprehensive test of the hypothesis that aggression in salmonids increases with the duration of stream residence. The intraspecific aggression of eleven juvenile salmonids was compared with their normal duration of stream residence. Salmonids maintained in 1 metre tanks and observed over two days could be separated into four groups based on statistical differences between the frequencies of aggressive behaviour. Non-anadromous Salvelinus fontinalis showed the highest levels of aggressive behaviour, followed by Oncorhynchus masou and O. mykiss (rainbow and steelhead trout). Least aggressive were the early migrants O. nerka (kokanee and sockeye salmon) and O. keta. The remaining species, O. rhodurus, O. kisutch, S. leucomaenis pluvius and Salmo trutta formed a moderately aggressive group. Aggressiveness was significantly and positively correlated with the duration of stream residence.     

The effects of introduced salmonids on two native stream‐dwelling salmonids through interspecific competition

Using an artificial stream, habitat use by two sympatric native salmonids in the presence and absence of introduced salmonid species was investigated experimentally. When only native white‐spotted charr Salvelinus leucomaenis and masu salmon Oncorhynchus masou were sympatric, they occupied different microhabitats. In the presence of introduced brown trout Salmo trutta or rainbow trout Oncorhynchus mykiss , however, white‐spotted charr and masu salmon were observed to use a similar habitat and interspecific competition between white‐spotted charr and masu salmon was initiated. The study suggested that the coexistence of native salmonids was negatively affected through interspecific competition between native and introduced salmonids.     

A proteinase associated with cortices of rainbow trout eggs and involved in fertilization-induced depolymerization of polysialoglycoproteins

A novel proteinase that acts on polysialoglycoprotein (PSGP) was found in the cortex fraction of the unfertilized eggs of rainbow trout. This enzyme (designated PSGPase) is responsible for specific depolymerization of cortical vesicular 200- to 9-kDa PSGP in vivo upon fertilization. We have succeeded in measuring the enzyme activity in an in vitro system by using 3H-labeled PSGP as the substrate. In the in vitro system PSGPase is active only at concentrations of NaCl below 40 mM and at low temperature (optimum temperature, about 16 degrees C), which are the conditions most suitable for egg activation.     

Molecular cloning and characterization of cDNAs coding for apopolysialoglycoproteins in cherry salmon (Oncorhynchus masou) eggs

Recently we have cloned the cDNAs and genomic DNAs for apopolysialoglycoproteins (apoPSGPs) of Salmo gairdneri (rainbow trout) [Sorimachi, H., Emori, Y., Kawasaki, H., Kitajima, K., Inoue, S., Suzuki, K., & Inoue, Y. (1988) J. Biol. Chem. 262, 17678-17684], and the sequence analyses have indicated that the mRNAs for apoPSGPs vary in length and contain different numbers of identical 39-bp repeating units encoding the tridecapeptide (Asp-Asp-Ala-Thr-Ser-Glu-Ala-Ala-Thr-Gly-Pro-Ser-Gly) as well as highly conserved sequences encoding pre-, pro-, and telo-peptide regions. In this study we isolated cDNA clones for yamame (cherry salmon, river resident form; Oncorhynchus masou ishikawai) apoPSGP using a genomic DNA fragment for rainbow trout apoPSGP as a probe. The nucleotide sequence analyses revealed that the structures of mRNAs for yamame apoPSGP including the noncoding regions are essentially identical to those for rainbow trout, showing 90% sequence identity. Within the repeating region, 4 bp out of the 39 were replaced, producing a different tridecapeptide, Asp-Asp-Ala-Thr-Ser-Glu-Ala-Ala-Thr-Gly-Pro-Ser-Ser. This tridecapeptide is unique to yamame and common among all cDNAs obtained from yamame. Genomic Southern blot analysis showed that the yamame apoPSGP genes constituted a multiple gene family with a similar gene organization to that of rainbow trout. Oligodeoxynucleotide probes (18 bases) synthesized based on specific sequences for the yamame repeating unit hybridized only to the yamame DNA and not to the rainbow trout DNA, and vice versa.(ABSTRACT TRUNCATED AT 250 WORDS)     

Polysialoglycoproteins of Salmonidae fish eggs. Complete structure of 200-kDa polysialoglycoprotein from the unfertilized eggs of rainbow trout (Salmo gairdneri)

Polysialoglycoproteins (PSGP) we first isolated from the unfertilized eggs of rainbow trout (Salmo gairderi) and now found to be a ubiquitous component of Salmonidae fish eggs are a novel type of glycoprotein. PSGP from rainbow trout has a molecular weight of 200 X 10(3), a low protein content (about 15% w/w), and a high sialic acid (N-glycolylneuraminic acid (NeuGc] content (about 60%, w/w). In any evaluation of the biological functions of PSGP, information about the complete structure of this unique macromolecular component is relevant. We have now completed the determination of the overall structural organization of the 200-kDa PSGP, and this is the first report of the complete structural analysis of this novel class of glycoprotein: (Asp)0-2-Ala-Thr*-Ser*-Glu-(Ala-Ala-Thr*-Gly-Pro-Ser-Gly-Asp-Asp-Ala-Thr *-Ser*- Glu)n-Ala-Ala-Thr*-Gly-Pro-Ser-Gly where * indicates the amino acid residues to which oligo- and/or polysialylglycan units are attached and n = 25. Thus the most outstanding structural features of PSGP isolated from the unfertilized eggs of rainbow trout are now the occurrence of (a) tandem repeats of a tridecapeptide and (b) an alpha-2----8-linked oligo(poly)sialyl group on each of the core oligosaccharide chains, i.e. GalNAc- beta 1----4(NeuGc alpha 2----3)GalNAc beta 1----3Gal beta 1----4Gal beta 1----3[----8NeuGc alpha 2)n----6)GalNAc alpha 1----Ser (or Thr), Fuc alpha 1----3GalNAc beta 1----3Gal beta 1----4Gal beta 1----3[----8NeuGc alpha 2)n ----6)GalNAc alpha 1----Ser (or Thr), GalNAc beta 1----3Gal beta 1----4Gal beta 1----3[----8NeuGc alpha 2)n----6)GalNAc alpha 1----Ser (or Thr), Gal beta 1----4Gal beta 1----3[----8NeuGc alpha 2)n----6)GalNAc alpha 1----Ser (or Thr), and Gal beta 1----3[----8NeuGc alpha 2)n----6) GalNAc alpha 1----Ser (or Thr).     

Distribution and molecular evolution of rhamnose-binding lectins in Salmonidae: isolation and characterization of two lectins from white-spotted Charr (Salvelinus leucomaenis) eggs

L-Rhamnose-binding lectins were isolated from white-spotted charr (Salvelinus leucomaenis) eggs to understand the distribution and molecular evolution of the lectins in Salmonidae. Only two L-rhamnose-binding lectins, named WCL1 and WCL3, were isolated from white-spotted charr eggs, though three lectins, named STL1, STL2, and STL3, had been obtained from steelhead trout (Oncorhynchus mykiss) eggs. The cDNAs of WCL1 and WCL3 included 1,245 and 838 bp nucleotides with open reading frames of 933 and 651 nucleotides, respectively, and encoded for the complete amino acid sequences of mature proteins consisted of 288 (WCL1) and 195 (WCL3) residues, and signal sequences of 23 and 22 residues, respectively. WCLs were composed of three (for WCL1) or two (for WCL3) tandemly repeated homologous domains, which consisted of about 95 amino acid residues, and showed 91 and 93% sequence identities to STL1 and STL3, respectively. The mRNAs of WCL1 and WCL3 were detected exclusively in liver and ovary, respectively, however, neither a protein nor mRNA corresponding to STL2 could be identified in white-spotted charr. The phylogenetic tree of the sequences encoding carbohydrate recognition domains of 7 lectins from 4 species shows 5 functional clusters and their evolutional process. These results indicate that multiple L-rhamnose-binding isolectins have diverged by gene duplication and exon shuffling to play various biological roles in each species.     

虹鳟spindlin基因克隆及不同倍性的表达分析

spindlin基因是减数分裂纺锤体相关因子, 为了研究spindlin基因在二倍体和三倍体雌性虹鳟减数分裂过程中出现的差异, 通过cDNA末端快速扩增(RACE)技术获得spindlin基因cDNA 4529 bp(GenBank登录号: MN378564), 其中3′非编码区(UTR)和5′非编码区(UTR)分别长3662 bp和141 bp, 开放阅读框(ORF)长726 bp, 编码241个氨基酸, 该蛋白质序列的相对分子量为28.3 kD, 理论等电点值为5.94, 无跨膜结构。同源性分析表明, 虹鳟(Oncorhynchus mykiss)与银大马哈鱼(Oncorhynchus kisutch)同源最高, 高达99.59%。系统发育进化树显示, 虹鳟与大鳞大马哈鱼(Oncorhynchus tshawytscha)和红点鲑(Salvelinus alpinus), 聚为一支。实时荧光定量(RT-PCR)结果显示, spindlin基因在二倍体雌性虹鳟卵巢、肾、肝、脾、肌、鳃、心、眼、肠和鳍组织中均有表达, 其中, 在卵巢中的表达量极显著高于其他组织(P<0.01)。对于二倍体雌性虹鳟, 在受精后240—300d (days post fertilization, dpf)发育阶段, spindlin基因在卵巢组织中的相对表达量显著下降。对于三倍体雌性虹鳟, 该基因在240—330 dpf阶段的表达量显著上升。在同一发育阶段中, spindlin基因在二倍体雌性虹鳟卵巢中的表达量较三倍体雌性虹鳟相对较高, 且均存在极显著差异(P<0.01)。通过免疫组化结果发现, 二倍体雌性虹鳟在240 dpf阶段, Spin蛋白在初级卵母细胞核内信号最强, 在270—330 dpf阶段逐渐减弱; 三倍体虹鳟卵巢在240—330 dpf发育阶段, 在卵原细胞中信号逐渐增强。减数分裂异常是性腺败育的关键原因, 研究结果表明三倍体虹鳟在减数分裂过程中出现异常与spindlin基因的低表达有关, 这可能是卵巢发育阻滞的原因之一。     

New tandem-repeating peptide structures in polysialoglycoproteins from the unfertilized eggs of kokanee salmon

New polysialoglycoproteins, designated PSGP(On), were isolated from the fertilized and unfertilized eggs of the kokanee salmon, Oncorhynchus nerka adonis. The polysialylglycan chains consisting of alpha-2,8-linked O-acetylated poly(N-glycolylneuraminyl) chains have recently been characterized. We have now determined the complete amino acid sequence of the tandem-repeating units of PSGP(On) from the unfertilized eggs of kokanee salmon and found that the following two distinct forms are present in PSGP(On) in almost identical amounts: [formula: see text] and [formula: see text] where * denotes the O-glycosylation site and mean value of m, n = about 20. Upon fertilization these high-molecular-weight forms of PSGP(On) were proteolytically cleaved to the corresponding repeating units, low-molecular-weight PSGP(On), by the action of a specific protease (PSGPase) at the position two residues set C-terminally to the Pro residue and N-terminally to the Asp residue, i.e. -Pro-Ser-Xaa-Asp-: [formula: see text] and [formula: see text].     

Use of a bacteriophage-derived endo-N-acetylneuraminidase and an equine antipolysialyl antibody to characterize the polysialyl residues in salmonid fish egg polysialoglycoproteins. Substrate and immunospecificity studies

Polysialoglycoproteins (PSGP), a class of glycoproteins containing oligo(poly)sialylglycan chains, are the major glycoprotein components in cortical alveoli of a number of Salmonidae fish eggs. Lake trout, Salvelinus namaycush, egg PSGP (PSGP(Sn)) differs from rainbow trout, Salmo gairdneri, egg PSGP (PSGP(Sg)) in its sialic acid composition; the former contains both N-acetyl- and N-glycolyl-D-neuraminic acid residues, designated Neu5Ac and Neu5Gc, while the latter contains only Neu5Gc residues. Fragmentation analysis of oligo(poly)sialyl chains in lake trout PSGP(Sn) has established that there are two distinct types of oligo(poly)sialyl structures in this PSGP molecule, namely alpha-2,8-linked oligo/poly(Neu5Ac) and alpha-2,8-linked oligo/poly(Neu5Gc). No hybrid structure having both Neu5Ac and Neu5Gc residues in the fragment oligosialic acids was detected. These two distinct PSGP preparations from eggs of lake trout and rainbow trout have been used to compare their immunoreactivity with anti-polysialyl antibodies (H.46) and sensitivity to a bacteriophage-derived (Escherichia coli K1F) endo-N-acetylneuraminidase (Endo-N). H.46 was found to cross-react only with lake trout PSGP(Sn) in immunodiffusion assays but not with rainbow trout PSGP(Sg), indicating that H.46 is a specific probe for alpha-2,8-linked poly(Neu5Ac) but not for poly(Neu5Gc). In contrast, Endo-N was found to catalyze the hydrolysis of both alpha-2,8-linked poly (Neu5Ac) and poly(Neu5Gc), so that this enzyme can be used as a diagnostic reagent for detecting both types of polysialic acids. H.46 was used in indirect immunofluorescence experiments to localize PSGP(Sn) in cortical alveoli isolated from lake trout eggs.     

Isolation of a Loma salmonae variant: biological characteristics and host range

A Salvelinus -infecting variant of Loma salmonae , derived from naturally-infected Chinook salmon Oncorhynchus tshawytscha by serial passage through brook trout Salvelinus fontinalis , has been isolated and amplified. Loma salmonae SV ( Salvelinus -variant) has a high preference for species of Salvelinus (brook trout and Arctic charr S. alpinus ) and low virulence and preference for species of Oncorhynchus (rainbow trout O. mykiss , Chinook salmon, cohoSalmon O. kisutch ) or Salmo (Atlantic salmon Salmo salar ). Although this variant of L. salmonae was different from the original, the differences do not justify describing it as a new species, although definitive determination is pending.     

Feeding behaviour in some teleosts is triggered by single amino acids primarily through olfaction

The present study investigated behavioural responses of naïve rainbow trout Oncorhynchus mykiss , lake charr Salvelinus namaycush , lake whitefish Coregonus clupeaformis and goldfish Carassius auratus to food extracts as well as selected amino acids (at 10⁻⁶ M) and related chemicals in a flow‐through behaviour trough. Cysteine, the most potent olfactory stimulating amino acid determined electrophysiologically, enhanced locomotor activity, an initial arousal behaviour, in all species examined, in exactly the same fashion as did food extracts. The increased locomotor activity was followed by distinct species‐specific search behavioural patterns: 1) bottom searching in rainbow trout; 2) surfacing and jumping in lake charr; 3) exploratory behaviour against the trough window in lake whitefish; 4) gravel pecking in goldfish. Olfactory‐stimulating neutral amino acids alanine and serine and gustatory‐stimulating imino acid proline were effective, to varying degrees, in eliciting feeding behaviour. Arginine and glutamate suppressed the locomotor activity in rainbow trout, but triggered feeding behaviour in the other species. Agmatine, a decarboxylated arginine, stimulated feeding behaviour in all species tested, except rainbow trout. The observed behavioural responses were in close accordance with the electrophysiological threshold and specificity. Together, the present data demonstrate that single amino acids and closely related chemicals initiate feeding behaviour primarily by olfaction, and interchangeably and complemented by gustation, in naive fishes.     

Failure of interspecies androgenesis in salmonids

Androgenetic development of salmonid embryos was induced in recipient oocytes from the same or other species (intra- or interspecies androgenesis). Parameters for induced androgenesis were investigated in brown trout Salmo trutta and brook trout Salvelinus fontinalis . Reciprocal androgenetic and control crosses were conducted among fishes from three genera: Oncorhynchus (rainbow trout, O. mykiss ), Salmo (brown trout) and Salvelinus (brook trout), and within two genera: Salmo (brown trout and Atlantic salmon, S. salar ) and Salvelinus (brook trout and Arctic charr, S. alpinus ). Live hatched androgenetic progenies were obtained in all intraspecies variants, where oocytes and sperm originated from the same species. Interspecies androgenesis resulted in no viable larvae, despite the fact that most hybrid controls and intraspecies androgenetic individuals were viable. When recipient oocytes originated from other genera (interspecific intergeneric androgenesis), embryonic development ceased in early developmental stages, except for haploid controls of brook trout produced in eggs of brown trout. Survival of embryos to the eyed-egg stage was relatively high in the intrageneric androgenesis experiment. Nevertheless, none of these embryos survived to hatching. Some of the presumed Atlantic salmon individuals developing in brown trout eggs contained maternal DNA, questioning the accuracy of enucleation using irradiation. The inability to induce interspecific androgenesis among the examined salmonid species may have been the result of substantial kariotypical and developmental differences between spermatozoal donors and oocyte recipients, causing an incompatibility between maternal cytoplasmic regulatory factors and the paternal nuclear genome.     

Redd superimposition by introduced rainbow trout,oncorhynchus mykiss, on native charrs in a japanese stream

Spawning redd superimposition of introduced, spring-spawning rainbow trout,Oncorhynchus mykiss, on native, fall-spawning Dolly varden,Salvelinus malma, and white-spotted charr,S. leucomaenis, were examined in a small stream in Hokkaido, Japan. The stream reaches in which Dolly Varden and white-sported charr redds were observed in fall 1997 greatly overlapped with the reaches in which rainbow trout redds were recorded in spring 1998. Spawning microhabitats were also similar between trout and the two charr species. Thirteen and 3% of Dolly Varden and white-spotted charr redds, respectively, were superimposed by rainbow trout redds. The eggs or alevins in the disturbed charr redds were potentially damaged because charrs were not likely to have emerged from the redds before the superimposition occurred. In sufficiently great abundance, introduced rainbow trout may negatively impact native charr populations by dislodging the latter’s spawning redds.     

Does light intensity affect self‐feeding and food wastage in group‐held rainbow trout and white‐spotted charr?

The self‐feeding rhythms of rainbow trout Oncorhynchus mykiss and white‐spotted charr Salvelinus leucomaenis were studied when group‐held fishes ( n  = 10 per group) were fed using self‐feeders under two different light intensities (50 lx, 16 μW cm⁻² and 700 lx, 215 μW cm⁻²) during the light phase of the light‐dark cycle. Food wastage was also measured. At 50 lx, all groups of rainbow trout learned to operate the self‐feeder within 4 days, whereas it took up to 25 days for all groups at 700 lx. In contrast, all groups of white‐spotted charr learned self‐feeding within 17 days, irrespective of light intensity. These results, although non‐significant, suggest that lower light intensities can stimulate instrumental learning in rainbow trout, but not white‐spotted charr. In rainbow trout, the total number of trigger actuations for the entire experimental period was significantly higher at 50 rather than 700 lx, although this may have been related to delayed learning at 700 lx. There was no significant effect in white‐spotted charr. Growth rate (assessed using the thermal growth coefficient) was also higher in rainbow trout but not white‐spotted charr at 50 rather than 700 lx, although this difference was non‐significant. Light intensity had no significant effect on food wastage in either rainbow trout or white‐spotted charr, and it did not appear to affect the proportion of trigger actuations during the light phase. Clear diurnal feeding rhythms were observed in both species and these were classified into four categories: uniform, dawn, dusk and crepuscular. At 50 lx, fish from both species generally fed in temporally localized periods at either dawn and dusk, whilst feeding was predominantly uniform during the light phase at 700 lx.     

A divergent non-classical class I gene conserved in salmonids

 Complementary DNA for two class I genes of the rainbow trout, Oncorhynchus mykiss, were characterized. MhcOnmy-UBA*01 is similar to Onmy-UA-C32 and the classical major histocompatibility complex class I genes of other fish species, whereas Onmy-UAA*01 is divergent from all class I genes so far characterized. Onmy-UAA*01 is expressed at lower levels than Onmy-UBA*01. Although Onmy-UAA*01 exhibits restriction fragment length polymorphism on Southern blotting, the encoded protein is highly conserved. Two allotypes, which differ only by substitution at amino acid position 223 of the α₃ domain, have been defined. Onmy-UAA*01 has an exon-intron organization like other class I genes and contains a Tc1-like transposon element in intron III. Orthologues of Onmy-UAA*01 have been characterized in four other species of salmonid. Between four species of Oncorhynchus, UAA*01 proteins differ by only 2–6 amino acids, whereas comparison of Oncorhynchus with Salmo trutta (brown trout) reveals 14–16 amino acid differences. The Onmy-UAA*01 gene has properties indicative of a particularly divergent non-classical class I gene. Received: 22 September 1998 / Revised: 24 November 1998     

Complex evolution of vitellogenin genes in salmonid fishes

Vitellogenins (Vtg) are usually encoded by small multigene families containing up to six genes. With 20 tandemly arranged genes, the rainbow trout ( Oncorhynchus mykiss) is an exception to this rule. PCR amplification, cloning and sequence analysis of Vtg genes in other salmonid species revealed the existence of two paralogous gene clusters, designated Vtg-A and Vtg-B. Southern hybridization showed that the number of genes varies from 2 to 30 copies from one species to another, as well as between the two gene clusters. All Coregonus, Thymallus, Salmo and Salvelinus species studied have both gene clusters, while Oncorhynchus species possess only the Vtg-A locus. Phylogenetic trees constructed from Vtg sequences revealed conflicting nodes with the consensus tree based on morphological and anatomical data. Vtg sequences support the grouping ( Salmo, ( Salvelinus, Oncorhynchus)) instead of the accepted consensus ( Salvelinus, ( Salmo, Oncorhynchus)). Structural data on gene organization also support the contention that Salvelinus and Oncorhynchus are sister taxa. Evolutionary implications for the Vtg gene clusters in salmonids are discussed.     

The role of alpha 2-macroglobulin in furunculosis: a comparison of rainbow trout and brook trout.

1. The molecular basis for the high survival rate of rainbow trout, Oncorhynchus mykiss, infected with furunculosis was investigated. 2. Alpha 2-macroglobulin (alpha 2M), a major serum protease inhibitor, was partially purified from rainbow trout and brook trout, Salvelinus fontinalis, sera; the latter species shows marked disease susceptibility. 3. It is shown that a 10-fold species-based difference in alpha 2M inhibitory activity exists against a furunculosis associated bacterial protease. 4. A possible basis for the observed disparity is discussed. 5. Results suggest that the high mol. wt form of teleost (trout) albumin is a dimer composed of two 85,000 subunits.     

Organization and primary sequence of multiple genes coding for the apopolysialoglycoproteins of rainbow trout

We have shown that the mRNAs for apopolysialoglycoproteins (apoPSGP) of rainbow trout contain various numbers of a repetitive sequence of 39 base-pairs encoding mature apoPSGP, and that this sequence is bordered by highly homologous 5' and 3' regions encoding pre-, pro- and telopeptides. These mRNAs are thought to be transcribed from different genes that constitute a large multiple gene family (more than 100 members). Here, we have determined the structures of several members of the apoPSGP gene family. The results show that two of three genomic DNA fragments contain two independent apoPSGP genes in the same orientation with unrelated sequences intervening. Five characterized genes have essentially the same organization and sequence. Each gene has four exons, and CAAT and TATA sequences were found in the 5'-flanking regions. However, two noteworthy differences were observed among the five genes; a diversity in the number of the 39 base-pair repeats, also observed among the cDNA clones, and a one-base polymorphism in the 39 base-pair repeat, which causes an amino acid change. This polymorphism was not detected among the cDNA clones obtained. The boundary positions of the genes are various and contain no transposon-like structures. The variation in the number of repeats and the absence of a rule for bordering positions of the genes suggest that apoPSGP genes may have been amplified by gene duplications, unequal recombination, and selection of chromosomes having larger numbers of apoPSGP genes.