Testing the polar auxin transport model with a selective plasma membrane H+-ATPase inhibitor

Auxin is unique among plant hormones in that its function requires polarized transport across plant cells. A chemiosmotic model was proposed to explain how polar auxin transport is derived by the H⁺ gradient across the plasma membrane (PM) established by PM H⁺-adenosine triphosphatases (ATPases). However, a classical genetic approach by mutations in PM H⁺-ATPase members did not result in the ablation of polar auxin distribution, possibly due to functional redundancy in this gene family. To confirm the crucial role of PM H⁺-ATPases in the polar auxin transport model, we employed a chemical genetic approach. Through a chemical screen, we identified protonstatin-1 (PS-1), a selective small-molecule inhibitor of PM H⁺-ATPase activity that inhibits auxin transport. Assays with transgenic plants and yeast strains showed that the activity of PM H⁺-ATPases affects auxin uptake as well as acropetal and basipetal polar auxin transport. We propose that PS-1 can be used as a tool to interrogate the function of PM H⁺-ATPases. Our results support the chemiosmotic model in which PM H⁺-ATPase itself plays a fundamental role in polar auxin transport.     

Multi-bit biomemory consisting of recombinant protein variants, azurin

In this study a protein-based multi-bit biomemory device consisting of recombinant azurin with its cysteine residue modified by site-directed mutagenesis method has been developed. The recombinant azurin was directly immobilized on four different gold (Au) electrodes patterned on a single silicon substrate. Using cyclic voltammetry (CV), chronoamperometry (CA) and open circuit potential amperometry (OCPA) methods the memory function of the fabricated biodevice was validated. The charge transfer occurs between protein molecules and Au electrode enables a bi-stable electrical conductivity allowing the system to be used as a digital memory device. Data storage is achieved by applying redox potentials which are within the range of 200mV. Oxidation and open circuit potentials with current sensing were used for writing and reading operations respectively. Applying oxidation potentials in different combinations to each Au electrodes, multi-bit information was stored in to the azurin molecules. Finally, the switching robustness and reliability of the proposed device has been examined. The results suggest that the proposed device has a function of memory and can be used for the construction of nano-scale multi-bit information storage device.     

Regulation of lipopolysaccharide-induced inflammatory response by heat shock protein 27 in THP-1 cells

HSP27 is a member of the small HSP family which has been linked to different signaling pathways regulating critical cellular functions. But the role of HSP27 in LPS-induced inflammatory signaling pathways is still unclear. In the present study, both overexpression and RNA interference experiments indicated that HSP27 increased LPS-induced expression of iNOS and COX-2 and release of NO/PGE2 through enhancing NF-κB but not MAPK activation. The effects of HSP27 on LPS-induced iNOS/COX-2 expression and relative signaling cascade were closely related with the phosphorylation of HSP27. Further studies have shown that HSP27-regulated LPS-induced activation of NF-κB by interacting with TRAF6 and increasing the association of TRAF6-IKKγ. This could be a probable mechanism by which HSP27 modulates LPS-induce inflammatory signaling pathways. Thus, HSP27 may play a potential role in regulating inflammatory responses in immunologic system.     

Molecular cloning and expression of key gene encoding hypothetical DNA polymerase from B. mori parvo-like virus

BmPLV-Z is the abbreviation for Bombyx mori parvo-like virus (China isolate). This is a novel virus with two single-stranded linear DNA molecules, viz., VD1 (6543 bp) and VD2 (6022 bp), which are encapsidated respectively into separate virions. Analysis of the deduced amino acid sequence of VD1-ORF4 indicated the existence of a putative DNA-polymerase with exonuclease activity, possibly involved in the replication of BmPLV-Z. In the present study, a recombinant baculovirus was constructed to express the full length of the protein encoded by the VD1-ORF4 gene (3318 bp). In addition, a 2163-bp fragment amplified from the very same gene was cloned into prokaryotic expression vector pET-30a and expressed in E.coli Rosetta 2 (DE3) pLysS. The expressed fusion protein was employed to immunize New Zealand white rabbits for the production of an antiserum, afterwards used for examining the expression of the protein encoded by VD1-ORF4 gene in Sf-9 cells infected with recombinant baculovirus. Western blot analysis of extracts from thus cells infected revealed a specific band of about 120 kDa, thereby indicating that the full length protein encoded by the VD1-ORF4 gene had been successfully and stably expressed in Sf-9 cells.     

Syntheses and crystal structures of three diorganoltin(IV) macrocycles

Three novel macrocyclic diorganotin(IV) compounds of the type: {[R₁₀(SnO)₃(SnOH)₂]H_nXO_m}₂ · L (n=1, m=4, R=PhCH₂, X=P, L=0, 1; n=0, m=4, R=PhCH₂, X=S, L=4H₂O, 2; n=0, m=3, R=n-Bu, X=N, L=0, 3) were synthesized by the reaction of (PhCH₂)₂SnCl₂ with Na₂H_nXO₄ (n=1, X=P; n=0, X=S) or (n-Bu)₂SnCl₂ with NaNO₃. All the compounds 1, 2 and 3 are characterized by elemental, IR and X-ray diffraction analyses. X-ray data reveal that a macrocyclic structure with two centrosymmetric ladders of hydrolysis exists in the crystals of the three compounds. The geometry about each tin atom involved is trigonal bipyramidal.     

High Temperature and Salinity Enhance Soil Nitrogen Mineralization in a Tidal Freshwater Marsh

Soil nitrogen (N) mineralization in wetlands is sensitive to various environmental factors. To compare the effects of salinity and temperature on N mineralization, wetland soils from a tidal freshwater marsh locating in the Yellow River Delta was incubated over a 48-d anaerobic incubation period under four salinity concentrations (0, 10, 20 and 35‰) and four temperature levels (10, 20, 30 and 40°C). The results suggested that accumulated ammonium nitrogen (NH₄ ⁺-N) increased with increasing incubation time under all salinity concentrations. Higher temperatures and salinities significantly enhanced soil N mineralization except for a short-term (≈10 days) inhibiting effect found under 35‰ salinity. The incubation time, temperature, salinity and their interactions exhibited significant effects on N mineralization (P<0.001) except the interactive effect of salinity and temperature (P>0.05), while temperature exhibited the greatest effect (P<0.001). Meanwhile, N mineralization processes were simulated using both an effective accumulated temperature model and a one-pool model. Both models fit well with the simulation of soil N mineralization process in the coastal freshwater wetlands under a range of 30 to 40°C (R² = 0.88–0.99, P<0.01). Our results indicated that an enhanced NH₄ ⁺-N release with increasing temperature and salinity deriving from the projected global warming could have profound effects on nutrient cycling in coastal wetland ecosystems.