Junzhe Zhang

An EREBP/AP2-type protein in Triticum aestivum was a DRE-binding transcription factor induced by cold, dehydration and ABA stress

Abstract.We characterize one transcription factor of DRE-binding proteins (TaDREB1) that was isolated from a drought-induced cDNA library of wheat (Triticum aestivum L.). TaDREB1 contains one conserved EREBP/AP2 domain, and shows similarity with Arabidopsis thaliana DREB family members in both overall amino-acid sequences and the secondary structure arrangement within the DNA-binding motifs. In yeast one-hybrid system, TaDREB1, can specially activate the genes fused with the promoter containing three tandemly repeated copies of the wild-type DRE sequence: TACCGACAT. In different wheat cultivars, the Ta DREB1 gene is induced by low temperature, salinity and drought; and the expression of Wcs120 that contains DRE motifs in its promoter is closely related to the expression of TaDREB1. These results suggest that TaDREB1 functions as a DRE-binding transcription factor in wheat. We also observed the dwarf phenotype in transgenic rice (T0) overexpressing TaDREB1.

A soybean gene encoding a proline-rich protein is regulated by salicylic acid, an endogenous circadian rhythm and by various stresses

Abstract.A cDNA clone of a soybean gene encoding a proline-rich protein (PRP) was characterized and designated SbPRP (Soybean Proline-rich Protein). The SbPRP protein is a putative bimodular protein of 126 amino acids with a proline-rich domain and a hydrophobic cysteine-rich domain plus a signal peptide at the N terminal. Southern analysis indicates the presence of a single copy of the SbPRP gene in the soybean genome. The SbPRP gene expression was investigated and the results demonstrate that it accumulates in leaves and epicotyls of soybean seedlings, but not in cotyledons, hypocotyls and roots. The SbPRP mRNA was also expressed in response to salicylic acid and virus infection. In addition, the SbPRP gene transcription was regulated by circadian rhythm, salt stress, drought stress and plant hormones. These results indicate that the SbPRP gene might play a role in plant responses to multiple internal and external factors.

Expression of the plasma membrane H+-ATPase gene in response to salt stress in a rice salt-tolerant mutant and its original variety

Abstract Plasma membrane (PM) H+-ATPase plays an important role in the establishment and maintenance of ion homeostasis. To investigate its expression in the rice salt-tolerant mutant M-20 and the original variety 77–170 during salt stress, a cDNA fragment corresponding to the PM H+-ATPase gene was obtained by PCR from rice japonica variety 77–170 and designated as OSA3. Sequence analysis of OSA3 revealed its high homology with two other published PM H+-ATPase genes, OSA1 and OSA2, in rice. Southern-blot analysis detected a RFLP between M-20 and 77–170, and one copy of the OSA3 gene was mapped to a position on rice chromosome 12 where a salt tolerance QTL was closely located. The expression of the PM H+-ATPase gene, as revealed by the OSA3 fragment, was compared between M-20 and 77–170. The results demonstrated that M-20 shoots accumulated less transcripts than 77–170 shoots at a later stage of salt treatment, and M-20 showed high expression at 300 mM NaCl while 77–170 reached its maximum at 200 mM NaCl. In roots, the difference in the level of the PM H+-ATPase gene expression between stressed and non-stressed plants was substantially greater in M-20 than that in 77–170. The relative abundance of PM H+-ATPase gene transcripts in M-20 roots may indicate the active role of this gene in the strict control of Na+ and Cl+ uptake into root symplast and apoplast, and further translocation into the shoot, hence leading to the reduced gene expression of M-20 shoots under salt-stress conditions.

A salt-responsive receptor-like kinase gene regulated by the ethylene signaling pathway encodes a plasma membrane serine/threonine kinase

NTHK1 is a salt-inducible ethylene receptor gene in tobacco. Transgenic tobacco plants for this gene show reduced ethylene sensitivity. Using cDNA microarray analysis, we were able to identify those genes that have different expression levels between NTHK1 transgenic plants and wild-type plants under salt stress conditions. One of these, AtLecRK2, which encodes a receptor-like kinase with an extracellular lectin-like domain, was characterized in detail in the present study. AtLecRK2 contains a signal peptide, an extracellular lectin-like domain, a single transmembrane domain and a cytoplasmic protein kinase domain. AtLecRK2 is transcribed in the root, flower and leaf but not in the stem. In wild-type Arabidopsis, salt stress induced the transcription level of AtLecRK2, whereas in the transgenic NTHK1 Arabidopsis induction of the AtLecRK2 transcript was inhibited and retarded. AtLecRK2 was constitutively overexpressed in the ethylene-overproducer mutant, eto1-1, and could be induced by ethylene. However, in the ethylene-insensitive mutant, ein2-1, the salt-induced expression pattern of AtLecRK2 was the same as that in wild-type plants. The results demonstrate that the induction of AtLecRK2 in response to salt stress is regulated by the ethylene signaling pathway. The induction was inhibited by the ethylene receptor, NTHK1, while it was independent of EIN2. The kinase activity of AtLecRK2 was also studied. We found that that AtLecRK2 can be autophosphorylated and has serine/threonine kinase activities. The subcellular localization of AtLecRK2-GFP in onion epidermal cells indicates that AtLecRK2 is localized on the plasma membrane.

L-theanine protects the APP (Swedish mutation) transgenic SH-SY5Y cell against glutamate-induced excitotoxicity via inhibition of the NMDA receptor pathway.

As a natural analogue of glutamate, l-theanine is the unique amino acid derivative in green tea. Although its underlining mechanisms are not yet clear, it has been suggested that l-theanine treatment may prove beneficial to patients with neurodegenerative diseases. In this study, we investigated the neuroprotective effect and its mechanism of l-theanine in an in vitro model of Alzheimers disease by using the human APP (Swedish mutation) transgenic SH-SY5Y cell. Amyloid beta (Abeta) neurotoxicity was triggered by l-glutamate in this cell line. Additionally, l-theanine significantly attenuated l-glutamate-induced apoptosis at similar levels to those seen with the NMDA receptor inhibitor MK-801 in the stably expressing APP Swedish mutation SH-SY5Y cells which over-generated Abeta. Meanwhile, the activation of c-Jun N-terminal kinase and caspase-3 induced by l-glutamate was suppressed by l-theanine. We also found that cells treated with l-theanine showed decreased production of nitric oxide resulting from the down-regulated protein levels of inducible nitric oxide synthase (iNOS) and neuronal nitric oxide synthase (nNOS). These results indicate that the inhibition of the NMDA subtype of glutamate receptors and its related pathways is the crucial point of the neuroprotective effect of l-theanine in the cell model. Thus, our present study supports the notion that l-theanine may provide effective prophylaxis and treatment for Alzheimers disease.

A two-component gene (NTHK1) encoding a putative ethylene-receptor homolog is both developmentally and stress regulated in tobacco

Abstract The full-length of a two-component gene NTHK1 (Nicotiana tabacum histidine kinase-l) was isolated from tobacco (N. tabacum var. Xanthi) using a previously obtained NTHK1 cDNA fragment as a probe. Sequence analysis revealed that NTHK1 shared high homology with LeETR4 from tomato and encoded an ethylene- receptor homolog. The predicted NTHK1 protein had a putative signal peptide, three transmembrane domains, a histidine kinase domain and a receiver domain. The putative autophosphorylation site at His378 and the phosphate receiver site at Asp689 were also identified. By using the in situ hybridization technique, NTHK1 mRNA was detected during flower organ development. It is also highly expressed in the processes of pollen formation and embryo development. The expression of NTHK1 in response to wounding and other stresses was investigated using competitive RT-PCR. The results demonstrated that NTHK1 was inducible upon wounding (cutting). Floating of the cut leaf pieces in 0.5× MS, with shaking, led to a relatively rapid and strong expression. This phenomenon was confirmed by the in situ hybridization results. In addition to the up-regulation by wounding, NTHK1 expression was also induced following NaCl and PEG treatment, indicating a possible role for NTHK1 in multiple stress responses.

Comparative Pulmonary Toxicity of Two Ceria Nanoparticles with the Same Primary Size

Ceria nanoparticles (nano-ceria) have recently gained a wide range of applications, which might pose unwanted risks to both the environment and human health. The greatest potential for the environmental discharge of nano-ceria appears to be in their use as a diesel fuel additive. The present study was designed to explore the pulmonary toxicity of nano-ceria in mice after a single exposure via intratracheal instillation. Two types of nano-ceria with the same distribution of a primary size (3–5 nm), but different redox activity, were used: Ceria-p, synthesized by a precipitation route, and Ceria-h, synthesized by a hydrothermal route. Both Ceria-p and Ceria-h induced oxidative stress, inflammatory responses and cytotoxicity in mice, but their toxicological profiles were quite different. The mean size of Ceria-p agglomerates was much smaller compared to Ceria-h, thereby causing a more potent acute inflammation, due to their higher number concentration of agglomerates and higher deposition rate in the deep lung. Ceria-h had a higher reactivity to catalyzing the generation of reactive oxygen species (ROS), and caused two waves of lung injury: bronchoalveolar lavage (BAL) inflammation and cytotoxicity in the early stage and redox-activity-evoked lipid peroxidation and pro-inflammation in the latter stage. Therefore, the size distribution of ceria-containing agglomerates in the exhaust, as well as their surface chemistry are essential characteristics to assess the potential risks of using nano-ceria as a fuel additive.

Where Does the Transformation of Precipitated Ceria Nanoparticles in Hydroponic Plants Take Place

Cerium oxide nanoparticles (CeO2 NPs) have been found to be partly biotransformed from Ce(IV) to Ce(III) in plants, yet the transformation process and mechanism are not fully understood. Here, we try to clarify the specific site and necessary conditions for the transformation of precipitated CeO2 NPs in hydroponic cucumber plants. Three different treatment modes were adopted according to whether the NPs were incubated with roots all the time or not. Results showed that exposure modes significantly affect the translocation and transformation of CeO2 NPs. In the normal exposure mode, Ce was present as a Ce(IV) and Ce(III) mixture in the roots and shoots, and the proportion of Ce(III) in the shoots was enhanced obviously with the increase of exposure time. The results of short-time incubation and petiole exposure modes suggested that CeO2 NPs could not be reduced within a short incubation time (3 h) or be further reduced inside the plant tissues. It was deduced that root surfaces are the sites, and the physicochemical interaction between the NPs and root exudates at the nanobio interface is the necessary condition for the transformation of CeO2 NPs in plant systems. These results will contribute to understanding the transformation mechanism of CeO2 and other metal-based NPs and properly evaluate their ecological effects.

Toxicity and transformation of graphene oxide and reduced graphene oxide in bacteria biofilm

Impact of graphene based material (GNMs) on bacteria biofilm has not been well understood yet. In this study, we compared the impact of graphene oxide (GO) and reduced graphene oxide (rGO) on biofilm formation and development in Luria-Bertani (LB) medium using Escherichia coli and Staphylococcus aureus as models. GO significantly enhanced the cell growth, biofilm formation, and biofilm development even up to a concentration of 500mg/L. In contrast, rGO (≥50mg/L) strongly inhibited cell growth and biofilm formation. However, the inhibitory effects of rGO (50mg/L and 100mg/L) were attenuated in the mature phase (>24h) and eliminated at 48h. GO at 250mg/L decreased the reactive oxygen species (ROS) levels in biofilm and extracellular region at mature phase. ROS levels were significantly increased by rGO at early phase, while they returned to the same levels as control at mature phase. These results suggest that oxidative stress contributed to the inhibitory effect of rGO on bacterial biofilm. We further found that supplement of extracellular polymeric substances (EPS) in the growth medium attenuated the inhibitory effect of rGO on the growth of developed biofilm. XPS results showed that rGO were oxidized to GO which can enhance the bacterial growth. We deduced that the elimination of the toxicity of rGO at mature phase was contributed by EPS protection and the oxidation of rGO. This study provides new insights into the interaction of GNMs with bacteria biofilm.

Inorganic nitrogen wet deposition: Evidence from the North-South Transect of Eastern China

We examined the spatio-temporal variation of dissolved inorganic nitrogen (DIN) deposition in eight typical forest ecosystems of Eastern China for three consecutive years. DIN deposition exhibited an increasing gradient from north to south, with N-NH4(+) as the predominant contributor. DIN deposition in precipitation changed after interaction with the forest canopy, and serious ecological perturbations are expected in this region. DIN deposition presented seasonal fluctuations, which might be ascribed to agricultural activity, fossil-fuel combustion and environmental factors (i.e., wind direction, soil temperature). Notably, N fertilizer use (FN), energy consumption (E), and precipitation (P) jointly explained 84.3% of the spatial variation in DIN deposition, of which FN (27.2%) was the most important, followed by E (24.8%), and finally P (9.3%). The findings demonstrate that DIN deposition is regulated by precipitation mainly via anthropogenic N emissions, and this analysis provides decision-makers a novel view for N pollution abatement.