Effect of Bt genetic engineering on indirect defense in cotton via a tritrophic interaction

We present a tritrophic analysis of the potential non-intended pleiotropic effects of cry1Ac gene derived from Bacillus thurigiensis (Bt) insertion in cotton (DeltaPine 404 Bt Bollgard® variety) on the emission of herbivore induced volatile compounds and on the attraction of the egg parasitoid Trichogramma pretisoum (Hymenoptera: Trichogrammatidae). Both the herbivore damaged Bt variety and its non-Bt isoline (DeltaPine DP4049 variety) produced volatiles in higher quantity when compared to undamaged plants and significantly attracted the egg parasitoids (T. pretiosum) when compared to undamaged plants. However, Trichogramma pretiosum did not differentiate between the transgenic and nontransgenic varieties, suggesting that the ratios between the compounds released by herbivory damaged -Bt cotton and herbivory damaged-nonBt cotton did not change significantly. Finally, no detrimental effect of the Bt genetic engineering was detected related to the volatile compounds released by Bollgard cotton on the behavior of the natural enemy studied.     

Acclimation of barley to changes in light intensity: chlorophyll organization

Barley seedlings (Hordeum vulgare L. cv. Boone) were grown at 20°C with a 16h/8h light/dark cycle of either high (H) intensity (550 mole m^-2 s^-1) or low (L) intensity (55 mole m^-2 s^-1) white light. Plants were transferred from high to low (H L) or low to high (L H) light intensity at various times from 4 to 8 d after leaf emergence from the soil. Primary leaves were harvested at the beginning of the photoperiod and a 3 cm apical segment removed for analysis. H control plants had greater chlorophyll (Chl) per leaf area and higher Chl a/b ratios than L controls. Analysis of Chl-protein complexes revealed that H and L plants had the same percentage of total Chl (62–65%) associated with Photosystem II (PS II), but that the organization of Chl within PS II was different. H plants contained lower levels of light-harvesting complex (LHC-II) and higher levels of the PS II complex CPa compared with L plants. Leaf Chl content and Chl organization within PS II were sensitive to changes in light intensity. In H L plants, leaf Chl content decreased, Chl a/b ratio decreased, and a redistribution of Chl from CPa to LHC-II occurred during acclimation to low light. Acclimation of L H plants to high light involved an increase in leaf Chl content, an increase in Chl a/b ratio, and a decrease in LHC-II. In contrast, the level of photosystem I related Chl-protein complexes (CP1 + CP1a) was similar in all light treatments. The light acclimation process occurred slowly over a period of 6 to 8 d in H L and L H plants.Abbreviations DMF dimethylformamide - H control plants grown under high light intensity - H L plants transferred from high to low light intensity - L control plants grown under low light intensity - L H plants transferred from low to high light intensity Cooperative investigations of the United States Department of Agriculture, Agricultural Research Service, and the North Carolina Agricultural Research Service, Raleigh, NC. Paper No. 11989 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC 27695-7643, USA.     

Ischemia-Induced Changes in Extracellular Lévels of Striatal Cyclic AMP: Role of Dopamine Neurotransmission

Dopamine has been demonstrated to be involved in the development of ischemic neuronal damage in the striatum. This detrimental effect of dopamine may involve activation of second messenger systems, such as the cyclic AMP (cAMP) cascade, which may enhance the susceptibility of striatal neurons to ischemia. In the present study, we have evaluated the relationship between ischemia-induced changes in cAMP and dopamine neurotransmission. Microdialysis probes were implanted in both striata, and a D1 antagonist (SCH-23390, 100 microM) was administered through one probe and modified Ringer's solution through the other. After a stabilization period, rats (n = 6) were subjected to 20 min of ischemia by two-vessel occlusion plus hypotension. Extracellular samples were collected from both striata, before, during, and after ischemia, and analyzed for cAMP by radioimmunoassay. Ischemia induced a significant increase in extracellular cAMP (means +/- SE, fmol/microliter; baseline: 4.35 +/- 1.1, ischemia: 12.2 +/- 1.98), which was also observed at 4 h of recirculation (mean level of 8.45 +/- 1.14). Treatment with the D1 antagonist significantly inhibited the rise in extracellular cAMP during ischemia and recirculation. These results indicate that an ischemia-induced surge in dopamine and activation of D1 receptors are involved in the generation of cAMP during ischemia and recirculation. Because activation of the adenylate cyclase cascade may modulate the effects of glutamate, generation of cAMP through this pathway may play a role in facilitating the injurious effects of dopamine during ischemia.     

Genetic dissection of aroma volatile compounds from the essential oil of peach fruit: QTL analysis and identification of candidate genes using dense SNP maps

Volatile organic compounds (VOCs) in plants are involved in aroma and pest resistance. These compounds form a complex mixture whose composition is specific to species and often to varieties. Despite their importance as essential factors that determine peach fruit quality, understanding of molecular, genetic, and physiological mechanisms underlying aroma formation is limited. The aim of this study was the identification in peach of quantitative trait loci (QTLs) for fruit VOCs to understand their genetic basis using an F1 population of 126 seedlings deriving from the cross between “Bolero” (B) and “OroA” (O), two peach cultivars differing in their aroma profile. Dense single nucleotide polymorphism (SNP) and SSR maps covering the eight linkage groups of the peach genome were constructed by genotyping with the International Peach SNP Consortium peach SNP array v1, and data for 23 VOCs with high or unknown “odor activity value” were obtained by gas chromatography–mass spectrometry analysis of fruit essential oil in the years 2007 and 2008. A total of 72 QTLs were identified, most consistent in both years. QTLs were identified for the 23 VOCs studied, including three major QTLs for nonanal, linalool, and for p-menth-1-en-9-al stable in both years. Collocations between candidate genes and major QTLs were identified taking advantage of the peach genome sequence: genes encoding two putative terpene synthases and one lipoxygenase (Lox) might be involved in the biosynthesis of linalool and p-menth-1-en-9-al, and nonanal, respectively. Implications for marker-assisted selection and future research on the subject are discussed.     

Inhibition of copper absorption by zinc

Copper and zinc interact at the intestinal mucosal level, affecting copper absorption. Amino acids, such as histidine, may affect the absorption of these two elements by chelating these cations. The two mechanisms could have additive potential. This possibility was investigated using a duodenal-jejunal single-pass perfusion procedure in anesthetized rats. Copper absorption and tissue retention from solutions containing 0.1 mM copper were determined in the presence of either no zinc or equimolar zinc, or at a zinc/copper ratio of 10/1, either without histidine or with histidine at a 10/1 or 20/1 ratio to copper. Copper removal from the intestinal lumen was decreased by zinc, and further reduced by increasing concentrations of histidine. There was a greater accumulation of copper in the small intestine, reaching a maximum with a 10-fold excess of histidine. With zinc at a 10/1 ratio to copper, the addition of a 10- or 20-fold molar excess of histidine further decreased the net uptake of copper from the perfusate while greater copper accumulation in the tissue occurred. Histidine thus enhances the inhibitory effects of zinc on copper absorp|tion, suggesting the application of convergent mechanisms for diminishing copper uptake. This could be relevant for the treatment of Wilson’s disease.     

Modeling post-translational modifications and cancer-associated mutations that impact the heterochromatin protein 1α-importin α heterodimers

Heterochromatin protein 1α (HP1α) is a protein that mediates cancer-associated processes in the cell nucleus. Proteomic experiments, reported here, demonstrate that HP1α complexes with importin α (IMPα), a protein necessary for its nuclear transport. This data is congruent with Simple Linear Motif (SLiM) analyses that identify an IMPα-binding motif within the linker that joins the two globular domains of this protein. Using molecular modeling and dynamics simulations, we develop a model of the IMPα-HP1α complex and investigate the impact of phosphorylation and genomic variants on their interaction. We demonstrate that phosphorylation of the HP1α linker likely regulates its association with IMPα, which has implications for HP1α access to the nucleus, where it functions. Cancer-associated genomic variants do not abolish the interaction of HP1α but instead lead to rearrangements where the variant proteins maintain interaction with IMPα, but with less specificity. Combined, this new mechanistic insight bears biochemical, cell biological, and biomedical relevance.     

Seasonality and interspecific competition shape individual niche variation in co‐occurring tetra fish in Neotropical streams

The drivers of intraspecific niche variation and its effects on species interactions are still unclear, especially in species‐rich Neotropical environments. Here, we investigated how ecological opportunity and interspecific competition affect the degree of individual trophic specialization and the population niche breadth in tetra fish. We studied the four ecologically similar species (Psalidodon aff. gymnodontus, P. aff. paranae, P. bifasciatus, and Bryconamericus ikaa) in subtropical headwater streams (three sites with two co‐occurring species and three sites with only one species). We sampled fish in two contrasting seasons (winter/dry and summer/wet) and quantified their trophic niches using gut content analysis. Psalidodon bifasciatus was the only species distributed over all the sampled streams. We observed seasonal differences in population trophic niche breadth of P. bifasciatus just when this species co‐occurred with P. aff. gymnodontus. These findings confirm the complex nature of the effects of interspecific competition, depending, for instance, on the identity of the competitor. The degree of individual specialization of P. bifasciatus was higher in the winter, and it was not influenced by the presence of another species. Conversely, the other two Psalidodon species studied presented greater individual specialization in the summer, when fish consumed a higher proportion of allochthonous items (terrestrial insects and seeds), and there were no effects only for B. ikaa. Herein, our results suggest that seasonality in food‐resource availability is a major driver of niche variation and it has the potential to play an important role in how these similar tetra species interact and coexist. Abstract in Portuguese is available with online material.     

Vacuolar H+-ATPase in human breast cancer cells with distinct metastatic potential: distribution and functional activity

Tumor cells thrive in a hypoxic microenvironment with an acidic extracellular pH. To survive in this harsh environment, tumor cells must exhibit a dynamic cytosolic pH regulatory system. We hypothesize that vacuolar H⁺-ATPases (V-ATPases) that normally reside in acidic organelles are also located at the cell surface, thus regulating cytosolic pH and exacerbating the migratory ability of metastatic cells. Immunocytochemical data revealed for the first time that V-ATPase is located at the plasma membrane of human breast cancer cells: prominent in the highly metastatic and inconspicuous in the lowly metastatic cells. The V-ATPase activities in isolated plasma membranes were greater in highly than in lowly metastatic cells. The proton fluxes via V-ATPase evaluated by fluorescence spectroscopy in living cells were greater in highly than in lowly metastatic cells. Interestingly, lowly metastatic cells preferentially used the ubiquitous Na⁺/H⁺ exchanger and HCO₃^–-based H⁺-transporting mechanisms, whereas highly metastatic cells used plasma membrane V-ATPases. The highly metastatic cells were more invasive and migratory than the lowly metastatic cells. V-ATPase inhibitors decreased the invasion and migration in the highly metastatic cells. Altogether, these data indicate that V-ATPases located at the plasma membrane are involved in the acquisition of a more metastatic phenotype. metastasis; intracellular pH; migration; sodium ion/hydrogen ion exchanger; bicarbonate transport     

Synthetic lethal hubs associated with vincristine resistant neuroblastoma

Chemotherapy of cancer experiences a number of shortcomings including development of drug resistance. This fact also holds true for neuroblastoma utilizing chemotherapeutics as vincristine. We performed a comparative analysis of molecular and cellular mechanisms associated with vincristine resistance utilizing cell line as well as human tissue data. Differential gene expression analysis revealed molecular features, processes and pathways afflicted with drug resistance mechanisms in general, and specifically with vincristine significantly involving actin associated features. However, specific mode of resistance as well as underlying genotype of parental, vincristine sensitive cells apparently exhibited significant heterogeneity. No consensus profile for vincristine resistance could be derived, but resistance-associated changes on the level of individual neuroblastoma cell lines as well as individual patient profiles became clearly evident. Based on these prerequisites we utilized the concept of synthetic lethality aimed at identifying hub proteins which when inhibited promise to induce cell death due to a synthetic lethal interaction with down-regulated, chemoresistance associated features. Our screening procedure identified synthetic lethal hub proteins afflicted with actin associated processes holding synthetic lethal interactions to down-regulated features individually found in all chemoresistant cell lines tested, therefore promising an improved therapeutic window. Verification of such synthetic lethal hub candidates in human neuroblastoma tissue expression profiles indicated the feasibility of this screening approach for addressing vincristine resistance in neuroblastoma.     

Mycoplasma genitalium mg200 and mg386 genes are involved in gliding motility but not in cytadherence

Isolation and characterization of transposon-generated Mycoplasma genitalium gliding-deficient mutants has implicated mg200 and mg386 genes in gliding motility. The proposed role of these genes was confirmed by restoration of the gliding phenotype in deficient mutants through gene complementation with their respective mg386 or mg200 wild-type copies. mg200 and mg386 are the first reported gliding-associated mycoplasma genes not directly involved in cytadherence. Orthologues of MG200 and MG386 proteins are also found in the slow gliding mycoplasmas, Mycoplasma pneumoniae and Mycoplasma gallisepticum, suggesting the existence of a unique set of proteins involved in slow gliding motility. MG200 and MG386 proteins share common features, such as the presence of enriched in aromatic and glycine residues boxes and an acidic and proline-rich domain, suggesting that these motifs could play a significant role in gliding motility.