Congxin Xie

Dissecting the role of transforming growth factor-β1 in topmouth culter immunobiological activity: a fundamental functional analysis

Transforming growth factor-β1 (TGF-β1) has been proven to function primarily in mammalian immunobiological activity, but information regarding the immune role of TGF-β1 in teleosts is limited. In the present study, we describe the cDNA cloning and characterization of the TGF-β1 molecule in the topmouth culter. TGF-β1 is highly expressed in immune-related tissues of the culter, including the thymus, head kidney, and spleen. The recombinant culter TGF-β1 (cTGF-β1) was successfully expressed and purified in vitro, and the effects of cTGF-β1 on the mRNA expression of pro-inflammatory cytokines, such as TNF-α and IL-1β, in the absence or presence of LPS was determined in culter peripheral blood leukocytes. cTGF-β1 was found to have bipolar properties in inflammatory reactions. Additionally, to assess the immune role of teleost TGF-β1 in vivo, the expression of TGF-β1 in the culter thymus and spleen tissues induced by poly I:C were also examined. The expression of TGF-β1 was obviously up-regulated, as shown in the cell lines. However, the peak time of cTGF-β1 expression in the cell lines occurred significantly earlier than in the organic tissues under the same inducer, suggesting that the response of the teleost TGF-β1 molecule to exogenous infection depends on a more complicated signalling pathway in vivo than in vitro.

Analysis of genetic diversity in Glyptosternum maculatum (Sisoridae, Siluriformes) populations with AFLP markers

We determined the genetic diversity of geographic populations from three spawning grounds (Nyang River, Lhasa River, Shetongmon Reach of Yarlung Zangbo River) of Glyptosternum maculatum with amplified fragment length polymorphism (AFLP) markers. Five primer combinations detected 332 products, 51 of them (15.4%) were polymorphic in at least one population. The Shetongmon population was found to be the richest in genetic diversity as was indicated by the percentage of polymorphic loci and heterozygosity, followed by the Nyang population and the Lhasa population. The pair-wise genetic distance between populations were all very close, ranging from 0.0015 to 0.0042 with an average of 0.0024. The genetic distance was not proportional to the geographic distance. The analysis of molecular variance demonstrated that all variation occurred within populations. The average estimated fixation index (Fst) of three populations across all polymorphic loci was −0.0184, indicating the absence of genetic differences among the three sampled populations. The differentiation among populations was not significant, and population structure was weak. Our observations will help identify the genetic relationship among populations as the first approach to understand the genetic diversity of Glyptosternum maculatum.

Effects of resource availability and hydrological regime on autochthonous and allochthonous carbon in the food web of a large cross-border river (China)

Resource availability and flooding disturbance restrict the amount of energy available to the upper trophic level consumers and thus determine the trophic structure and energy mobilization in river food webs. In this study, we evaluated the availability of primary and secondary food resources, food web structure (determined by δ13C and δ15N) and relative contributions of autochthonous and allochthonous particulate carbon to aquatic consumers in the Irtysh River, which spans from northwest China to Kazakhstan and suffers from a long frozen period. Despite higher density and biomass, epilithic algae did not make large contributions to aquatic consumers due to the restriction of flow velocity, water depth and turbidity. Aquatic invertebrates specialized in utilization of terrestrial carbon sources, whereas fish varied from aquatic to riparian plants. Different resource use of aquatic consumers across the three reaches in the Irtysh River was ascribed to the spatial distribution of species and resource availability determined by flooding, flood scouring and dam construction. The trophic positions and food chain length at the upper reach were higher than those at the middle and lower reaches. These findings suggest that allochthonous carbon had an advantage over autochthonous carbon in supporting aquatic food webs of the Irtysh River. Higher availability of allochthonous particulate carbon might be relevant to intensive forest cover and high energy flood events in the Irtysh River.

The complete mitochondrial genome of Schizothorax pseudaksaiensis (Cypriniformes: Cyprinidae).

Abstract The complete mitochondrial genome of Schizothorax pseudaksaiensis was cloned and sequenced in the present study. The genome was 16,582 bp in size, which had a mostly conserved structural organization in comparison with that of other teleost fish. It consisted of 37 genes (13 protein-coding genes, 22 transfer RNA genes and 2 ribosomal RNA genes), and 2 main non-coding regions (the control region and the origin of the light strand replication). All protein-coding genes started with ATG except for COX1, which began with GTG. However, the termination codons of 13 protein-coding genes varied with TAA, TA, T or TAG. The overall base composition of S. pseudaksaiensis in descending order was A 30.18%, C 27.08%, T 25.37% and G 17.37%, with a slight A + T bias. The complete mitochondrial genome sequence may provide useful information for phylogenetic analysis and studies of population genetics of S. pseudaksaiensis.

The complete mitogenome sequence of Ptychobarbus dipogon (Cypriniformes: Cyprinidae)

Abstract The complete mitochondrial genome of Ptychobarbus dipogon is 16,787 bp in length, consisting of 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes and 2 non-coding regions: control region (CR) and origin of light-strand replication (OL). The gene order of P. dipogon mitogenome is similar to those observed in most other vertebrates. The complete mitogenome sequence of P. dipogon can provide useful data for further studies on population structure, phylogenetics and conservation genetics of this species.

Isolation and characterization of fifteen polymorphic tetranucleotide microsatellite loci in Schizopygopsis younghusbandi Regan

Schizopygopsis younghusbandi Regan is an important endemic fish in Tibet, China. Its wild population has been rapidly declining for the past few decades due to overfishing, dam construction and invasion of exotic fishes. To conserve natural resources and develop breeding stocks of S. younghusbandi, fifteen polymorphic tetranucleotide microsatellite loci were isolated and characterized in 45 individuals collected from the Yarlung Tsangpo River in Tibet. The number of alleles per locus ranged from 6 to 32 with an average of 17.87. The expected heterozygosity and Shannon–Wiener diversity index ranged from 0.454 to 0.951 and from 0.931 to 3.201, respectively. These microsatellite loci will be useful for future population genetic analysis and resource conservation of S. younghusbandi.

Age and growth of Schizothorax waltoni (Cyprinidae: Schizothoracinae) in the Yarlung Tsangpo river, China

ABSTRACT To better understand the biology of Schizothorax waltoni, the age structure and growth characteristics of S. waltoni were examined. The standard length (SL) range was 41–642 mm and the body weight (BW) range was 1.1–3788.1 g. Otoliths continually grew with increasing SL and increasing age, but asymmetrically over time. One annulus was formed each year, between April and July. Estimated age range was 4–37 yr for males, 4–40 yr for females, and 1–9 yr for those of undetermined sex. The SL–BW relationship was described as BW = 1.365 × 10−5 SL2.984 for females, BW = 1.238 × 10−5 SL2.999 for males, and BW = 3.664 × 10−5 SL2.800 for undetermined specimens. The von Bertalanffy function was used to model the observed length-at-age data as Lt = 644.3 {1 − exp [−0.084(t − 0.247)]} for females, and Lt = 586.2 {1 − exp [−0.084(t + 2.250)]} for males. Females grew faster than males. Knowledge of this species’ characteristics of slow growth and a long life will be useful for establishing reasonable management practices for its conservation.

Complete mitochondrial genome of Abramis brama orientalis Berg (cypriniformes, Cyprinidae, Leuciscinae).

Abstract In this study, we cloned and sequenced the complete mitochondrial genome of Abramis brama orientalis Berg. The genome was 16,610 bp (LR) in length and consisted of 13 protein-coding genes, 22 tRNA genes, 2 ribosomal RNA genes and 2 main non-coding regions [the control region (CR) and the origin of the light strand replication], the gene composition and order of which was similar to those reported from other fish mitochondrial genomes. The overall base composition of the heavy strand was T 26.7%, C 26.5 %, A 30.0% and G 16.8%, with a slight A + T bias of 56.7%. This mitogenome sequence data would play an important role in population genetics and phylogenetic analysis of the Leuciscinae.

Reproductive biology of Schizopygopsis younghusbandi Regan 1905 (Cyprinidae: Schizothoracinae) in the middle reaches of Yarlung Tsangpo River, China

The reproductive biology of Schizopygopsis younghusbandi (Cyprinidae: Schizothoracinae) was studied by 719 individuals that collected from August 2008 to August 2009 in the middle reaches of Yarlung Tsangpo River, China. We coupled monthly variations of the gonadosomatic index (GSI), monthly proportions of the macroscopic maturity stages with size distribution of oocytes to evaluate spawning seasons. Taken as a set, these results indicated that S. younghusband i spawned from March to April with high degree of the spawning synchronicity. The standard lengths and the ages at 50% maturity for male were 222 mm and 4.4 year, and 308 mm and 7.0 year for female. In addition, the estimated mean fecundity and mean relative fecundity were 18682 and 57.8 eggs per g body weight. The fecundity of S. younghusbandi increased linearly with increasing of standard length and body weight. This study provides details about the S. younghusbandi reproduction suggesting that may be this species is vulnerable to exploitation in the middle reaches of Yarlung Tsangpo River.

The complete mitochondrial genome of Perca schrenkii (Perciformes: Percidae)

Abstract The complete mitochondrial genome of Perca schrenkii was obtained in the present study. The total length of the mitogenome was 16 536 bp in accordance with other teleost fish. It consisted of 37 genes (13 protein-coding genes, 22 transfer RNA genes and 2 ribosomal RNA genes) and 2 main non-coding regions (the control region and the origin of the light strand replication). All protein-coding genes started with ATG except for COX1, which began with GTG. However, the termination codons of 13 protein-coding genes were varied with TAA, TA, T or TAG. The overall base composition in descending order was T 27.9%, C 27.7%, A 27.1% and G 17.4%, with a slight A + T bias. The complete mitochondrial genome sequence may provide important information for phylogenetic analysis and studies on the population genetics of P. schrenkii.