Brassinosteroids (BRs), a class of plant steroid hormones, play a significant role in the amelioration of various biotic and abiotic stresses. In order to further explore and elaborate their roles in plants subjected to chilling stress, suspension cultured cells of Chorispora bungeana with or without 24-epibrassinolide (EBR) application were exposed to 4 and 0°C for 5 days. The EBR treated cells exhibited higher viability after exposure to low temperatures compared with the control. Under chilling stress, reactive oxygen species (ROS) levels and lipid peroxidation were increased in the cultured cells, which were significantly inhibited by EBR application. The activities of antioxidative enzymes such as ascorbate peroxidase (APX), catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) were increased during chilling treatments, and these increases were more significant in the EBR applied suspension cells. The EBR treatment also greatly enhanced contents of ascorbic acid (AsA) and reduced glutathione (GSH) under chilling stress. From these results, it can be concluded that EBR could play the positive roles in the alleviation of oxidative damage caused by ROS overproduction through enhancing antioxidant defense system, resulting in improving the tolerance of C. bungeana suspension cultures to chilling stress.

Trehalose is a chemical chaperone known to protect a variety of organisms against cold stress. Members of the genus Arthrobacter, which belongs to the Actinomycetales group, exhibit strong resistance to stress conditions, but exactly how trehalose synthesis is regulated in conditions of cold stress is still unknown. Here, we report that Arthrobacter strain A3, which was isolated from the alpine permafrost, has only two trehalose synthesis pathways (OtsA/B and TreS), while other Arthrobacter spp. have three. Mutants and immunoblot analyses indicate that trehalose is mainly synthesized via OtsA at low temperatures in Arthrobacter strain A3. Therefore, we have focused on the regulation of OtsA expression during cold shock. The results indicated that both low temperature and accumulation of trehalose can inhibit OtsA expression. The elongation factor Tu, which binds to OtsA, stabilizes the expression of OtsA in the cold.

In this study, six bacterial community structures were analyzed from the Dunde ice core (9.5-m-long) using 16S rRNA gene cloning library technology. Compared to the Muztagata mountain ice core (37-m-long), the Dunde ice core has different dominant community structures, with five genus-related groups Blastococcus sp./Propionibacterium, Cryobacterium-related., Flavobacterium sp., Pedobacter sp., and Polaromas sp. that are frequently found in the six tested ice layers from 1990 to 2000. Live and total microbial density patterns were examined and related to the dynamics of physical-chemical parameters, mineral particle concentrations, and stable isotopic ratios in the precipitations collected from both Muztagata and Dunde ice cores. The Muztagata ice core revealed seasonal response patterns for both live and total cell density, with high cell density occurring in the warming spring and summer months indicated by the proxy value of the stable isotopic ratios. Seasonal analysis of live cell density for the Dunde ice core was not successful due to the limitations of sampling resolution. Both ice cores showed that the cell density peaks were frequently associated with high concentrations of particles. A comparison of microbial communities in the Dunde and Muztagata glaciers showed that similar taxonomic members exist in the related ice cores, but the composition of the prevalent genus-related groups is largely different between the two geographically different glaciers. This indicates that the micro-biogeography associated with geographic differences was mainly influenced by a few dominant taxonomic groups.

Gut microbiota has become a topical issue in unraveling the research mechanisms underlying disease onset and progression. As an important and potential “organ,” gut microbiota plays an important role in regulating intestinal epithelial cell differentiation, proliferation, metabolic function and immune response, angiogenesis and host growth. More recently, zebrafish models have been used to study the interactions between gut microbiota and hosts. It has several advantages, such as short reproductive cycle, low rearing cost, transparent larvae, high genomic similarity to humans, and easy construction of germ-free (GF) and transgenic zebrafish. In our review, we reviewed a large amount of data focusing on the close relationship between gut microbiota and host health. Moreover, we outlined the functions of gut microbiota in regulating intestinal epithelial cell differentiation, intestinal epithelial cell proliferation, metabolic function, and immune response. More, we summarized major factors that can influence the composition, abundance, and diversity of gut microbiota, which will help us to understand the significance of gut microbiota in regulating host biological functions and provide options for maintaining the balance of host health.

Rapid amplification of cDNA ends was performed to isolate cold-regulated CbCOR15 (EF208112) from Chorispora bungeana. This alpine species is distributed in subnival areas. Transcripts were detected in the leaves, but not the roots, of plants acclimated to cold temperatures. Expression was induced at high levels at both 4°C and −4°C. In comparing its deduced protein sequence to that of AtCOR15a (cold-regulated 15a in Arabidopsis thaliana), the N terminus had less homology than the C terminus while still containing a region analogous to the chloroplast-targeted signal peptide of AtCOR15a. We also introduced CbCOR15, with the CaMV 35S promoter, into tobacco. Second-generation (T1) plants had significantly increased tolerance to chilling, as determined by their electrolyte leakage, chlorophyll content, and relative water content. Further freezing-stress experiments showed that the tolerance of transgenic lines was significantly greater than that of the nontransgenics. Although the degree of chilling and freezing tolerance in the transgenic plants was not directly correlated with the accumulated levels of CbCOR15, we could conclude that this gene confers cold tolerance.

The ability of iron to accept and donate electrons makes it important for plant growth, but it can also damage plants when they are under environmental stress. Ferritin, a protein encoded by the gene Fer, catalyzes the oxidation of Fe(2+) and subsequent storage of Fe(3+) within the mineral core. Ferritin may reduce the adverse effects of iron on Chorispora bungeana Fisch. & C.A. May during the course of cold stress. C. bungeana is a rare alpine subnival plant species that is highly resistant to a freezing environment. We have isolated and characterized the ferritin cDNA (CbFer) from C. bungeana. It is 975 bp in length with an open reading frame of 260 amino acids, corresponding to a protein of predicted molecular mass of 29.17 kDa and an isoelectric point of 5.44. Amino acid analysis of the polypeptides indicated that CbFer codes for a ferritin subunit plus a chloroplast-targeting transit peptide. Reverse transcription polymerase chain reaction analysis confirmed that CbFer was a tissue-specific gene since the expression could only be detected in leaves. The gene expression patterns were investigated in relation to cold stress (4 degrees C and -4 degrees C) and to various exogenous signals, including excessive iron, hydrogen peroxide (H(2)O(2)), and nitrogen monoxidum (NO). The amount of CbFer mRNA increased in response to low temperatures and gene expression at -4 degrees C was both more distinct and quicker than that at 4 degrees C. Two exogenous signals, excessive iron and H(2)O(2), upregulated the expression of the CbFer gene, but NO had no effect. The CbFer gene may play an important role in response to cold stress, while the expression of the gene during stress may be influenced by major and minor factors such as iron and H(2)O(2), respectively.

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The pathologic characteristics and toxicity mechanism of Pseudomonas aeruginosa are different in strains with different Type III secretion system (T3SS) genes. The T3SS gene based genotyping of P. aeruginosa strains is important to understand its virulence and predict the clinical outcomes. In this study, a rapid and automatable method for T3SS genotyping was developed using magnetic enrichment multiplex PCR and chemiluminescence. Three P. aeruginosa standard strains were analyzed using this method. The results showed that the chemiluminescent intensity of exoT, exoY, and exoS of these strains were 10 times greater than that of the control, and that their Q values were greater than 2.1. These results were consistent with the regular PCR and electrophoresis results, indicating that the method was reliable. Out of the 22 clinical isolates tested using this method, 100%, 72.7%, 95.5%, and 4.5% of the isolates contained exoT, exoY, exoS, and exoU genes, respectively. The isolates harbored either exoS or exoU gene, but not both. All genotyping results of the isolates were consistent with the information obtained using regular PCR and electrophoresis.