Ion conductance pathways in potato tuber (Solanum tuberosum) inner mitochondrial membrane

Single-ion channel activities were measured after reconstitution of potato tuber mitochondrial inner membranes into planar lipid bilayers. In addition to the recently described large-conductance Ca(2+)-activated potassium channel activity (Koszela-Piotrowska et al., 2009), the following mitochondrial ion conductance pathways were recorded: (i) an ATP-regulated potassium channel (mitoK(ATP) channel) activity with a conductance of 164+/-8pS, (ii) a large-conductance Ca(2+)-insensitive iberiotoxin-sensitive potassium channel activity with a conductance of 312 pS+/-23, and (iii) a chloride 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS)-inhibited channel activity with a conductance of 117 pS+/-4. In isolated non-phosphorylating potato tuber mitochondria, individual and combined potassium channel activities caused significant (up to 14mV) but not collapsing K(+)-influx-induced membrane potential depolarisation. Under phosphorylating conditions, the coupling parameters were unchanged in the presence of high K(+) level, indicating that plant K(+) channels function as energy-dissipating systems that are not able to divert energy from oxidative phosphorylation. A potato tuber K(+) channel that is ATP-, 5-hydroxydecanonic acid-, glybenclamide-inhibited and diazoxide-stimulated caused low cation flux, modestly decreasing membrane potential (up to a few mV) and increasing respiration in non-phosphorylating mitochondria. Immunological analysis with antibodies raised against the mammalian plasma membrane ATP-regulated K(+) channel identified a pore-forming subunit of the Kir-like family in potato tuber mitochondrial inner membrane. These results suggest that a mitoK(ATP) channel similar to that of mammalian mitochondria is present in potato tuber mitochondria.     

Exogenous melatonin expediently modifies proteome of maize (<Emphasis Type="Italic">Zea mays</Emphasis> L.) embryo during seed germination

Melatonin (N-acetyl-5-methoxytryptamine) has a great potential for plant biostimulation. Its role in plant physiology is intensively explored, and its important function in plant stress defence frequently underlined. Melatonin is particularly effective when applied as an additional factor of seed priming. In the presented research, hydroconditioning was chosen experimentally as optimal for maize (Zea mays L.) seeds. The following seed variants were compared: controlled non-treated, hydroprimed with water and hydroprimed with melatonin solutions 50 and 500 μM. To identify modifications in proteome of maize seeds caused by the applied hydroconditioning techniques, protein extracts of germinated seed embryos (24 h, 25 °C) were separated by 2D-PAGE. Next, obtained maps of proteomes were compared (statistically and graphically) using PDQuest software, and characteristic spots of proteins were analysed qualitatively by mass-spectrometric techniques and identified in the Mascot protein databases. Research helped to identify hydropriming-associated proteins, and for the first time those which were expressed only in the presence of melatonin. Study confirmed that suitably selected pre-sowing treatment with melatonin, by embryo proteome modification, effectively prepares plants to adverse environmental conditions. In melatonin treated seeds during the initial state of embryos growth, even under optimal conditions, additional antioxidative, detoxifying, anti-stresses proteins were synthesized. Moreover, the supply of energy from seed storage substances was pretty intensified. The presented results partially explain how melatonin acts in plant stress defence, and why plants with higher melatonin content have exhibited increased capacity for stress tolerance.     

Phylogenetic analysis of the tenascin gene family: evidence of origin early in the chordate lineage

Background  

Tenascins are a family of glycoproteins found primarily in the extracellular matrix of embryos where they help to regulate cell proliferation, adhesion and migration. In order to learn more about their origins and relationships to each other, as well as to clarify the nomenclature used to describe them, the tenascin genes of the urochordate Ciona intestinalis, the pufferfish Tetraodon nigroviridis and Takifugu rubripes and the frog Xenopus tropicalis were identified and their gene organization and predicted protein products compared with the previously characterized tenascins of amniotes.     

Photodynamic Inactivation of Candida albicans with Imidazoacridinones: Influence of Irradiance,Photosensitizer Uptake and Reactive Oxygen Species Generation

The increasing applicability of antifungal treatments, the limited range of available drug classes and the emergence of drug resistance in Candida spp. suggest the need for new treatment options. To explore the applicability of C. albicans photoinactivation, we examined nine structurally different imidazoacridinone derivatives as photosensitizing agents. The most effective derivatives showed a >10⁴-fold reduction of viable cell numbers. The fungicidal action of the three most active compounds was compared at different radiant powers(3.5 to 63 mW/cm²), and this analysis indicated that 7 mW/cm² was the most efficient. The intracellular accumulation of these compounds in fungal cells correlated with the fungicidal activity of all 9 derivatives. The lack of effect of verapamil, an inhibitor targeting Candida ABC efflux pumps, suggests that these imidazoacridinones are not substrates for ABC transporters. Thus, unlike azoles, a major class of antifungals used against Candida, ABC transporter-mediated resistance is unlikely. Electron paramagnetic resonance (EPR)-spin trapping data suggested that the fungicidal light-induced action of these derivatives might depend on the production of superoxide anion. The highest generation rate of superoxide anion was observed for 1330H, 1610H, and 1611. Singlet oxygen production was also detected upon the irradiation of imidazoacridinone derivatives with UV laser light, with a low to moderate yield, depending on the type of compound. Thus, imidazoacridinone derivatives examined in the present study might act via mixed type I/type II photodynamic mechanism. The presented data indicate lack of direct correlation between the structures of studied imidazoacridinones, cell killing ability, and ROS production. However, we showed for the first time that for imidazoacridinones not only intracellular accumulation is necessary prerequisite of lethal photosensitization of C. albicans, but also localization within particular cellular structures. Our findings present IA derivatives as efficient antifungal photosensitizers with a potential to be used in local treatment of Candida infection.