2015 Vol. 36, No. 1
Ruminant stomach lysozyme is a long established model of adaptive gene evolution. Evolution of stomach lysozyme function required changes in the site of expression of the lysozyme c gene and changes in the enzymatic properties of the enzyme. In ruminant mammals, these changes were associated with a change in the size of the lysozyme c gene family. The recent release of near complete genome sequences from several ruminant species allows a more complete examination of the evolution and diversification of the lysozyme c gene family. Here we characterize the size of the lysozyme c gene family in extant ruminants and demonstrate that their pecoran ruminant ancestor had a family of at least 10 lysozyme c genes, which included at least two pseudogenes. Evolutionary analysis of the ruminant lysozyme c gene sequences demonstrate that each of the four exons of the lysozyme c gene has a unique evolutionary history, indicating that they participated independently in concerted evolution. These analyses also show that episodic changes in the evolutionary constraints on the protein sequences occurred, with lysozyme c genes expressed in the abomasum of the stomach of extant ruminant species showing the greatest levels of selective constraints.
The coexistence of ecologically similar species sharing sympatric areas is a central issue of community ecology. Niche differentiation is required at least in one dimension to avoid competitive exclusion. From 2012-2014, by adopting the methods of mist-nets and point counts to evaluate spatial niche partitioning and morphological differentiations, we explored the coexistence mechanisms of seven sympatric fulvettas in Ailao Mountains, Ejia town, Yunnan Province, China. The microhabitats of these seven fulvettas were significantly different in elevation, roost site height and vegetation coverage, indicating a spatial niche segregation in different levels. Approximately, 90.30% of the samples were correctly classified by linear discriminant analysis (LDA) with correct rates at 91.20%-100%, except the White-browed fulvetta (Alcippe vinipectus) (65.4%) and the Streak-throated fulvetta (A. cinereiceps) (74.6%). The seven fulvettas were classified into four guilds based on their specific morphological characters, suggesting that the species in each guild use their unique feeding ways to realize resource partitioning in the overlapped areas. These finding indicate that through multi-dimensional spatial niche segregation and divergence in resource utilizing, the inter-specific competition among these seven fulvettas is minimized, whereas, coexistence is promoted.
In reptiles, habitat selection is the process whereby suitable habitat is selected that optimizes physiological functions and behavioral performance. Here, we used the brown forest skink (Sphenomorphus indicus) as a model animal and examined whether the frequency of active individuals, environmental temperature, illumination of activity area, and habitat type vary with different age classes. We surveyed the number of active individuals and measured environmental variables at Baiyunshan Mountain in Lishui, Zhejiang, China. We found no difference in the activity frequency of adult and juvenile S. indicus; the activity pattern of active individuals was bimodal. The mean environmental temperature selected by adults was higher than that selected by juveniles. The environmental temperature of active areas measured at 0900-1000 h and 1100-1200h was higher than at 1400-1500h; illumination of the active area at 1000-1200h was also higher than at 1400h-1600 h. The number of active individuals, the environmental temperature and illumination of activity areas showed pairwise positive correlation. There was a difference in habitat type between juveniles and adults whereby juveniles prefer rock habitats. We predict that active S. indicus select optimal habitats with different environmental temperatures and types to reach the physiological needs particular to their age classes.
Lamprotula leai is one of the most commercially important freshwater pearl mussels in China, but there is limited data on its genetic diversity and population structure. In the present study, 119 individuals from four major geographical populations were investigated using 15 microsatellite loci identified via cross-species amplification. A total of 114 alleles were detected, with an average of 7.6 alleles per locus (range: 2 to 21). Among the four stocks, those from Hung-tse Lake and Poyang Lake had the lowest (0.412) and highest (0.455) observed heterozygosity respectively. The polymorphism information content (PIC) ranged from 0.374 to 0.927 (mean: 0.907). AMOVA showed that 12.56% and 44.68% genetic variances were among populations and within individuals, respectively. Pairwise Fst ranged from 0.073 to 0.146, indicating medium genetic differentiation among the populations. In aggregate, our results suggest that inbreeding is a crucial factor accounting for deviations from Hardy–Weinberg equilibrium at 12 loci. Moreover, the genetic distance among four stocks ranged from 0.192 to 0.890. Poyang Lake and Hung-tse Lake were clustered together, joined with Dongting Lake and Anqing Lake. Given that specimens from Hung-tse Lake showed the highest average allele richness, expected heterozygosity and PIC, this location may be the source of the highest quality germplasm resources and the stock from this area may be the best for future breeding efforts.
Multidrug resistant (MDR) pathogen infections are serious threats to hospitalized patients because of the limited therapeutic options. A novel group of antibiotic candidates, antimicrobial peptides (AMPs), have recently shown powerful activities against both Gram-negative and Gram-positive bacteria. Unfortunately, the viability of using these AMPs in clinical settings remains to be seen, since most still need to be evaluated prior to clinical trials and not all of AMPs are potent against MDR clinical isolates. To find a connection between the characteristics of several of these AMPs and their effects against MDR pathogens, we selected 14 AMPs of animal origin with typical structures and evaluated their in vitro activities against clinical strains of extensive drug-resistant Acinetobacter baumannii, methicillin-resistant Staphylococcus aureus, extended spectrum β-lactamase-producing Pseudomonas aeruginosa and extended spectrum β-lactamase-producing Escherichia coli. Our results showed that these peptides' hydrophilic/hydrophobic characteristics, rather than their secondary structures, may explain their antibacterial effects on these clinical isolates. Peptides that are amphipathic along the longitudinal direction seemed to be effective against Gram-negative pathogens, while peptides with hydrophilic terminals separated by a hydrophobic intermediate section appeared to be effective against both Gram-negative and Gram-positive pathogens. Among these, cathelicidin-BF was found to inhibit all of the Gram-negative pathogens tested at dosages of no more than 16 mg/L, killing a pandrug-resistant A. baumannii strain within 2 h at 4×MICs and 4 h at 2×MICs. Tachyplesin III was also found capable of inhibiting all Gram-negative and Gram-positive pathogens tested at no more than 16 mg/L, and similarly killed the same A. baumannii strain within 4 h at 4×MICs and 2×MICs. These results suggest that both cathelicidin-BF and tachyplesin III are likely viable targets for the development of AMPs for clinical uses.
To explore the neural mechanisms mediating aging-related visual function declines, we compared the expressions of brain-derived neurotrophic factor (BDNF) and its high affinity receptor-tyrosine kinase B (TrkB) between young and old adult cats. Nissl staining was used to display neurons in each layer of the lateral geniculate nucleus (LGN). The BDNF- and TrkB receptor-immunoreactive neurons were labeled immunohistochemically, observed under optical microscope and photographed. Their neuronal density and immunoreactive intensity were measured. Results showed that the mean density of the Nissl stained neurons in each LGN layer were comparable between old and young adult cats, and their BDNF and TrkB proteins were widely expressed in all LGN layers. However, compared with young adult cats, both the density and optical absorbance intensity of BDNF- and TrkB-immunoreactive cells in each LGN layer in old cats were significantly decreased. These findings indicate that the decreased expressions of BDNF and TrkB proteins in the LGN may be an important factor inducing the compromised inhibition in the central visual nucleus and the functional visual decline in senescent individuals.
It is well known that excessive long-term alcohol consumption is harmful, especially in pregnant women. In the present study, the Kunming white mouse was used as an animal model and indirect immunofluorescence was performed to analyze the toxic effects of alcohol on early pre-implantation embryos. H3K9 acetylation immunofluorescence could not be detected in MII oocytes. H3K9 acetylation levels in the treatment group were higher than in the control group during the morula stage, and contrary to results during the blastocyst stage. Other stages showed no obvious differences for in vivo embryos. For in vitro embryos, almost no difference was found between the two experimental groups across all stages, and both groups showed increasing H3K9 acetylation levels (except at the 2-cell stage). This study shows that H3K9 acetylation levels in early pre-implantation embryos are notably impacted by excessive alcohol ingestion by females. These data are the first step in understanding the epigenetic mechanism of alcohol toxicity in early pre-implantation mouse embryos.
Since 1980, the white-browed crake (Porzana cinerea) has been experiencing an expansion from south of the Isthmus of Kra, northward to China. Recently, this species was observed in several locations throughout Southwest China, including Ningming and Baise, Guangxi (2012, 2013), and Xichang, Sichuan (2013). These sightings are the first distribution record of this species in mainland China, suggesting that the white-browed crake is following a natural species dispersal northward into mainland China from Southeast Asia.