Effect of sweet cherry genes PaLACS2 and PaATT1 on cuticle deposition,composition and permeability in Arabidopsis

The cuticular membrane (CM) of sweet cherry (Prunus avium L.) fruit is severely strained during development. Strain results from a cessation of CM deposition during early development and is possibly caused by a downregulation of genes involved in CM synthesis. The objectives of our study were to investigate the effects of ectopic expression of two sweet cherry genes, PaLACS2 (a putative long-chain acyl-CoA synthetase) and PaATT1 (a putative cytochrome P450 monooxygenase), in Arabidopsis thaliana (L.). Effects on the expression of endogenous LACS2, ATT1 and LACS1 genes, wax and cutin composition, and cuticle permeability were investigated in 13 transgenic lines. Of these, six lines are selected for presentation based on the magnitude of the response. The amount of cutin increased in the PaLACS2 overexpression line C-L-29 and in the complemented lacs2-1 knockout mutant line l-L-14, but overexpression had no effect on cutin composition or wax. Wax deposition decreased in the complemented knockout lines l-L-14 and l-L-21. Overexpressing PaATT1 in A. thaliana line C-A-6 had no significant effect on cutin and wax deposition. In the complemented knockout lines a-A-7 and a-A-12, cutin deposition increased, whereas wax deposition was unaffected. The permeability of the cuticle for water and toluidine blue decreased in the PaLACS2 and PaATT1 complemented knockout lines. The results suggest that (1) PaLACS2 and PaATT1 expressed in A. thaliana are involved in cutin biosynthesis, and (2) their functions are consistent with those of a typical long-chain acyl-CoA synthetase (PaLACS2) and of a cytochrome P450 monooxygenase (PaATT1).     

Vascular connections between the receptacle and empty achenes in sunflower (Helianthus annuus L.)

Empty achenes in sunflower, particularly in the centre of the capitulum, may be caused by poor vascularization. This hypothesis was tested by microscopic examination and translocation experiments. Phloem and xylem were identified by fluorescence of aniline-blue-stained callose and autofluorescence, respectively. Vascular strands that extended from the receptacle into empty achenes were regularly found in longitudinal sections. The phloem-mobile probe, carboxyfluorescein, was translocated from the receptacle to the pericarp and the testa of empty achenes. Similarly, (14)CO(2)-derived (14)C-photoassimilates moved into empty achenes. The observations suggest that empty achenes are both structurally and functionally connected with the vascular system of the receptacle. Hence, deficient vascular connections do not prevent seed filling in sunflower.     

Stereospecific hydrolysis of 3-(4-methoxyphenyl)glycidic ester in supercritical carbon dioxide by immobilized lipase

In the hydrolysis of racemic 3-(4-methoxyphenyl)glycidic acid methyl ester by immobilized Mucor miehel lipase in supercritical CO₂ the initial hydrolysis rate of the (2S,3R)-form was faster than the rate of the (2R,3S) -form. The stereoisomeric excess of the (2R,3S)-form reached 87 % at 53 % total conversion level. The water content of the reaction mixture and the initial concentration of the 3-(4-methoxyphenyl) glycidic acid methyl ester had no effect on isomeric purity. The reaction rate in supercritical CO₂ was considerably faster than in toluene/water -mixture.     

Short-term exercise affects cardiac function ex vivo partially via changes in calcium channel levels,without influencing hypoxia sensitivity

Journal of Physiology and Biochemistry - Exercise is known to improve cardiac recovery following coronary occlusion. However, whether short-term exercise can improve cardiac function and hypoxia...     

Stress responses to polycyclic aromatic hydrocarbons in Arabidopsis include growth inhibition and hypersensitive response-like symptoms

Polycyclic aromatic hydrocarbons (PAHs) are of global environmental concern because they cause many health problems including cancer and inflammation of tissue in humans. Plants are important in removing PAHs from the atmosphere; yet, information on the physiology, cell and molecular biology, and biochemistry of PAH stress responses in plants is lacking. The PAH stress response was studied in Arabidopsis (Arabidopsis thaliana) exposed to the three-ring aromatic compound, phenanthrene. Morphological symptoms of PAH stress were growth reduction of the root and shoot, deformed trichomes, reduced root hairs, chlorosis, late flowering, and the appearance of white spots, which later developed into necrotic lesions. At the tissue and cellular levels, plants experienced oxidative stress. This was indicated by localized H2O2 production and cell death, which were detected using 3, 3'-diaminobenzidine and trypan blue staining, respectively. Gas chromatography-mass spectrometry and fluorescence spectrometry analyses showed that phenanthrene is internalized by the plant. Gene expression of the cell wall-loosening protein expansin was repressed, whereas gene expression of the pathogenesis related protein PR1 was induced in response to PAH exposure. These findings show that (i) Arabidopsis takes up phenanthrene, suggesting possible degradation in plants, (ii) a PAH response in plants and animals may share similar stress mechanisms, since in animal cells detoxification of PAHs also results in oxidative stress, and (iii) plant specific defence mechanisms contribute to PAH stress response in Arabidopsis.     

Sal-type ABC-F proteins: intrinsic and common mediators of pleuromutilin resistance by target protection in staphylococci

The first member of the pleuromutilin (PLM) class suitable for systemic antibacterial chemotherapy in humans recently entered clinical use, underscoring the need to better understand mechanisms of PLM resistance in disease-causing bacterial genera. Of the proteins reported to mediate PLM resistance in staphylococci, the least-well studied to date is Sal(A), a putative ABC-F NTPase that—by analogy to other proteins of this type—may act to protect the ribosome from PLMs. Here, we establish the importance of Sal proteins as a common source of PLM resistance across multiple species of staphylococci. Sal(A) is revealed as but one member of a larger group of Sal-type ABC-F proteins that vary considerably in their ability to mediate resistance to PLMs and other antibiotics. We find that specific sal genes are intrinsic to particular staphylococcal species, and show that this gene family is likely ancestral to the genus Staphylococcus. Finally, we solve the cryo-EM structure of a representative Sal-type protein (Sal(B)) in complex with the staphylococcal 70S ribosome, revealing that Sal-type proteins bind into the E site to mediate target protection, likely by displacing PLMs and other antibiotics via an allosteric mechanism.