Kelthane degradation by genetically engineered Pseudomonas aeruginosa BS827 in a soil ecosystem

The aim of this study was to study the degradation of kelthane by Pseudomonas aeruginosa BS827, which carried the plasmid pBS3. This plasmid encodes naphthalene oxidation. The strain was able to survive in the presence of kelthane and to retain its degradative ability. Kelthane also stabilized the biodegradative plasmid that was preserved by 70 to 100% of the cell population. Cells deficient in Nah or Sal characters were less effective in degrading kelthane, whereas plasmid-free cells lost this ability completely. Evidently, the degradative activity of P. aeruginosa BS827 was conditioned by plasmid determinants coupled with genes of the plasmid pBS3 Nah region.     

The influence of medium composition on alkaloid biosynthesis by <Emphasis Type="Italic">Penicillium citrinum</Emphasis>

The fungus P. citrinum produces secondary metabolites, clavinet ergot alkaloids (EA), and quinoline alkaloids (quinocitrinines, QA) in medium with various carbon and nitrogen sources and in the presence of iron, copper, and zinc additives. Mannitol and sucrose are most favorable for EA biosynthesis and mannitol is most favorable for QA. Maximum alkaloid production is observed on urea. Iron and copper additives in the medium containing zinc ions stimulated fungal growth but inhibited alkaloid biosynthesis. The production of these secondary metabolites does not depend on the physiological state of culture, probably due to the constitutive nature of the enzymes involved in biosynthesis of these substances.     

Prognosis of Thyroid Nodules in Individuals Living in the Zhitomir Region of Ukraine

Objective

After the accident at the Chernobyl Nuclear Power Plant (CNPP), the incidence of thyroid cancer increased among children. Recently, a strong relationship between solid thyroid nodules and the incidence of thyroid cancer was shown in atomic bomb survivors. To assess the prognosis of benign thyroid nodules in individuals living in the Zhitomir region of Ukraine, around the CNPP, we conducted a follow-up investigation of screening data from 1991 to 2000 in the Ukraine.

Patients and Methods

Participants of this study were 160 inhabitants with thyroid nodules (nodule group) and 160 inhabitants without thyroid nodules (normal control group) intially identified by ultrasonography from 1991 to 2000. All participants were aged 0 to 10 years old and lived in the same area at the time of the accident. We performed follow-up screening of participants and assessed thyroid nodules by fine needle aspiration biopsy.

Results

Among the nodule group participants, the number and size of nodules were significantly increased at the follow-up screening compared with the initial screening. No thyroid nodules were observed among the normal control group participants. The prevalence of thyroid abnormality, especially nodules that could be cancerous (malignant or suspicious by fine needle aspiration biopsy), was 7.5% in the nodule group and 0% in the normal control group (P<0.001).

Conclusions

Our study indicated that a thyroid nodule in childhood is a prognostic factor associated with an increase in the number and size of nodules in individuals living in the Zhitomir region of Ukraine.     

Structural Proton Diffusion along Lipid Bilayers

For H⁺ transport between protein pumps, lateral diffusion along membrane surfaces represents the most efficient pathway. Along lipid bilayers, we measured a diffusion coefficient of 5.8 × 10⁻⁵ cm² s⁻¹. It is too large to be accounted for by vehicle diffusion, considering proton transport by acid carriers. Such a speed of migration is accomplished only by the Grotthuss mechanism involving the chemical exchange of hydrogen nuclei between hydrogen-bonded water molecules on the membrane surface, and the subsequent reorganization of the hydrogen-bonded network. Reconstitution of H⁺-binding sites on the membrane surface decreased the velocity of H⁺ diffusion. In the absence of immobile buffers, structural (Grotthuss) diffusion occurred over a distance of 100 μm as shown by microelectrode aided measurements of the spatial proton distribution in the immediate membrane vicinity and spatially resolved fluorescence measurements of interfacial pH. The efficiency of the anomalously fast lateral diffusion decreased gradually with an increase in mobile buffer concentration suggesting that structural diffusion is physiologically important for distances of ~10 nm.     

Genetic correlational analysis of glycogen synthase kinase-3 beta and prepulse inhibition in inbred mice

In humans, GSK-3β activity is diminished in schizophrenic patients as is prepulse inhibition of the startle response (PPI). We performed a genetic correlational analysis between published PPI values and frontal cortex GSK-3 activity analyzed in our laboratory in 10 inbred mouse strains. This methodology could indicate relevant parameters for study in an animal model. Indeed, we obtained significant correlations between the enzyme's activity and PPI measured by two different methods. This may indicate that investigation of the genetics of GSK-3β regulation holds promise for understanding some of the biochemical underpinnings of schizophrenia.     

Linear remodeling of helical virus by movement protein binding

Previously we have shown that encapsidated potato virus X (PVX) RNA was nontranslatable in vitro, but could be converted into a translatable form by binding of the PVX-coded movement protein (termed TGBp1) to one end of a polar helical PVX virion. We reported that binding of TGBp1 to coat protein (CP) subunits located at one extremity of the helical particles induced a linear destabilization of the CP helix, which was transmitted along the whole particle. Two model structures were used: (i) native PVX and (ii) artificial polar helical PVX-like particles lacking intact RNA (PVX(RNA-DEG)). Binding of TGBp1 to the end of either of these particles led to their destabilization, but no disassembly of the CP helix occurred. Influence of additional factors was required to trigger rapid disassembly of TGBp1-PVX and TGBp1-PVX(RNA-DEG) complexes. Thus: (i) no disassembly was observed unless TGBp1-PVX complex was translated. A novel phenomenon of TGBp1-dependent, ribosome-triggered disassembly of PVX was described: initiation of translation and few translocation steps were needed to trigger rapid (and presumably cooperative) disassembly of TGBp1-PVX into protein subunits and RNA. Importantly, the whole of the RNA molecule (including its 3'-terminal region) was released. The TGBp1-induced linear destabilization of CP helix was reversible, suggesting that PVX in TGBp1-PVX complex was metastable; (ii) entire disassembly of the TGBp1-PVX(RNA-DEG) complex (but not of the TGBp1-free PVX(RNA-DEG) particles) into 2.8S subunits was triggered under influence of a centrifugal field. To our knowledge, transmission of the linear destabilization along the polar helical protein array induced by a foreign protein binding to the end of the helix represents a novel phenomenon. It is tempting to suggest that binding of TGBp1 to the end of the PVX CP helix induced conformational changes in terminal CP subunits that can be linearly transferred along the whole helical particle, i.e. that intersubunit conformational changes may be transferred along the CP helix.     

C2H2 zinc finger-SET histone methyltransferase is a plant-specific chromatin modifier

Histone modification represents a universal mechanism for regulation of eukaryotic gene expression underlying diverse biological processes from neuronal gene expression in mammals to control of flowering in plants. In animal cells, these chromatin modifications are effected by well-defined multiprotein complexes containing specific histone-modifying activities. In plants, information about the composition of such co-repressor complexes is just beginning to emerge. Here, we report that two Arabidopsis thaliana factors, a SWIRM domain polyamine oxidase protein, AtSWP1, and a plant-specific C2H2 zinc finger-SET domain protein, AtCZS, interact with each other in plant cells and repress expression of a negative regulator of flowering, FLOWERING LOCUS C (FLC) via an autonomous, vernalization-independent pathway. Loss-of-function of either AtSWP1 or AtCZS results in reduced dimethylation of lysine 9 and lysine 27 of histone H3 and hyperacetylation of histone H4 within the FLC locus, in elevated FLC mRNA levels, and in moderately delayed flowering. Thus, AtSWP1 and AtCZS represent two main components of a co-repressor complex that fine tunes flowering and is unique to plants.     

Biological systems of the host cell involved in Agrobacterium infection

Genetic transformation of plants by Agrobacterium, which in nature causes neoplastic growths, represents the only known case of trans‐kingdom DNA transfer. Furthermore, under laboratory conditions, Agrobacterium can also transform a wide range of other eukaryotic species, from fungi to sea urchins to human cells. How can the Agrobacterium virulence machinery function in such a variety of evolutionarily distant and diverse species? The answer to this question lies in the ability of Agrobacterium to hijack fundamental cellular processes which are shared by most eukaryotic organisms. Our knowledge of these host cellular functions is critical for understanding the molecular mechanisms that underlie genetic transformation of eukaryotic cells. This review outlines the bacterial virulence machinery and provides a detailed discussion of seven major biological systems of the host cell–cell surface receptor arrays, cellular motors, nuclear import, chromatin targeting, targeted proteolysis, DNA repair, and plant immunity – thought to participate in the Agrobacterium‐mediated genetic transformation.     

Plant defense pathways subverted by Agrobacterium for genetic transformation

The soil phytopathogen Agrobacterium has the unique ability to introduce single-stranded transferred DNA (T-DNA) from its tumor-inducing (Ti) plasmid into the host cell in a process known as horizontal gene transfer. Following its entry into the host cell cytoplasm, the T-DNA associates with the bacterial virulence (Vir) E2 protein, also exported from Agrobacterium, creating the T-DNA nucleoprotein complex (T-complex), which is then translocated into the nucleus where the DNA is integrated into the host chromatin. VirE2 protects the T-DNA from the host DNase activities, packages it into a helical filament and interacts with the host proteins, one of which, VIP1, facilitates nuclear import of the T-complex and its subsequent targeting to the host chromatin. Although the VirE2 and VIP1 protein components of the T-complex are vital for its intracellular transport, they must be removed to expose the T-DNA for integration. Our recent work demonstrated that this task is aided by an host defense-related F-box protein VBF that is induced by Agrobacterium infection and that recognizes and binds VIP1. VBF destabilizes VirE2 and VIP1 in yeast and plant cells, presumably via SCF-mediated proteasomal degradation. VBF expression in and export from the Agrobacterium cell lead to increased tumorigenesis. Here, we discuss these findings in the context of the “arms race” between Agrobacterium infectivity and plant defense.Key words: Arabidopsis, defense response, proteasomal degradation, bacterial infection, F-box proteinAgrobacterium infection of plants consists of a chain of events that usually starts in physically wounded tissue which produces Plant defense pathways subverted by Agrobacterium for genetic transformation small phenolic molecules, such as acetosyringone (AS).¹ These phenolics serve as chemotactic agents and activating signals for the virulence (vir) gene region of the Ti plasmid.^2,3 The vir gene products then process the T-DNA region of the Ti plasmid to a single-stranded DNA molecule that is exported with several Vir proteins into the host cell cytoplasm, in which it forms a the T-DNA nucleoprotein complex (T-complex).^4,5 The plant responds to the coming invasion by expressing and activating several defense-related proteins,⁵ such as VBF⁶ and VIP1,⁷ aimed at suppressing the pathogen. However, the Agrobacterium has evolved mechanisms to take advantage of these host defense proteins.⁸ Some of the unique strategies for achieving this goal include (1) the use of VIP1 to bind the T-complex—via the VIP1 interaction with the T-DNA packaging protein VirE2,^9,10—and assist its nuclear import⁷ and chromatin targeting,¹¹ and (2) the use of VBF to mark VIP1 and its associated VirE2 for proteasomal degradation, presumably for uncoating the T-complex prior to the T-DNA integration into the plant genome.^6,12 Here, we examine these subversion strategies in the context of “arms race” between Agrobacterium and plants.