High efficiency versus maximal performance — The cause of oxidative stress in eukaryotes: A hypothesis

Degenerative diseases are in part based on elevated production of ROS (reactive oxygen species) in mitochondria, mainly during stress and excessive work under stress (strenuous exercise). The production of ROS increases with increasing mitochondrial membrane potential (ΔΨ_m). A mechanism is described which is suggested to keep ΔΨ_m at low values under normal conditions thus preventing ROS formation, but is switched off under stress and excessive work to maximize the rate of ATP synthesis, accompanied by decreased efficiency. Low ΔΨ_m and low ROS production are suggested to occur by inhibition of respiration at high [ATP]/[ADP] ratios. The nucleotides interact with phosphorylated cytochrome c oxidase (COX), representing the step with the highest flux-control coefficient of mitochondrial respiration. At stress and excessive work neural signals are suggested to dephosphorylate the enzyme and abolish the control of COX activity (respiration) by the [ATP]/[ADP] ratio with consequent increase of ΔΨ_m and ROS production. The control of COX by the [ATP]/[ADP] ratio, in addition, is proposed to increase the efficiency of ATP production via a third proton pumping pathway, identified in eukaryotic but not in prokaryotic COX. We conclude that ‘oxidative stress’ occurs when the control of COX activity by the [ATP]/[ADP] ratio is switched off via neural signals.     

Functional diversity of ant-associated bacterial communities

It was found that ants significantly affect the physiological activity and functional diversity of soil microbial communities, and redistribution of biophilic elements (C and N) down through the profile occurs in anthills compared to the control soil, as well as their accumulation in the underground part of the ant nests. A high urease activity was revealed in ant nests and ants. Functional dissimilarities of bacterial communities in all studied objects were determined by the multisubstrate test.     

Physiological and biochemical properties of the bacterial association of <Emphasis Type="Italic">Klebsiella terrigena</Emphasis> E6 and <Emphasis Type="Italic">Bacillus firmus</Emphasis> E3

Physiological and biochemical properties of the natural rhizospheric association of Klebsiella terrigena E6 and Bacillus firmus E3 were studied. It was demonstrated that this association fixed actively molecular nitrogen at a rate of 110 nmol ethylene per 1 mg protein per h. The dynamics of bacterial population in the association and in pure cultures were studied. The properties of this association depended on the ratio of its components; the maximal nitrogen fixation was recorded at a content of B. firmus E310 amounting to 15% of the total cell number. It was demonstrated that the stability basis of this association was the specific interactions via its components via metabolites—phenol and para-hydroxybenzoic acid—as well as via nitrogen fixation, respiration, and pH of the medium. A scheme of the interactions between the components of association is shown.     

Intron-containing hairpin RNA interference vector for OBP8 show promising mortality in peach potato aphid

Myzus persicae is a devastating pest affecting potato production. Intron-containing hairpin RNA (ihpRNA) silenced the odorant-binding protein 8 (OBP8) for enhanced protection against Myzus persicae in potatoes. OBP8 was isolated from M. persicae, sequenced, with the allotment of GenBank ID. ERNAi was used to design siRNA targets from OBP8 with no off-targets. Multiple Sequence Alignment show M. persicae OBP8 resemblance with Acyrthosiphon pisum, Rhopalosiphum maidis, Aphis fabae, and Sitobion avenae. dsRNA-OBP8 (7 µg/µL) oral feeding resulted in a 69% mortality, and 58% OBP8 reduced expression 8D post-feeding compared to control. Golden Gate cloning is used for RNA interference taking advantage of type IIs restriction enzyme Eco31I. ihpRNA-OBP8 introduced by agroinfiltration in Solanum tuberosum. Transgenic S. tuberosum fed Myzus show 57.6% mortality and 49% reduction in OBP8 expression 8D post-feeding, compared to control. This work proves OBP8 as promising ihpRNA targets in potato and related crops for whom Myzus is a destructive pest.

     

Tricellulin is a tight-junction protein necessary for hearing

The inner ear has fluid-filled compartments of different ionic compositions, including the endolymphatic and perilymphatic spaces of the organ of Corti; the separation from one another by epithelial barriers is required for normal hearing. TRIC encodes tricellulin, a recently discovered tight-junction (TJ) protein that contributes to the structure and function of tricellular contacts of neighboring cells in many epithelial tissues. We show that, in humans, four different recessive mutations of TRIC cause nonsyndromic deafness (DFNB49), a surprisingly limited phenotype, given the widespread tissue distribution of tricellulin in epithelial cells. In the inner ear, tricellulin is concentrated at the tricellular TJs in cochlear and vestibular epithelia, including the structurally complex and extensive junctions between supporting and hair cells. We also demonstrate that there are multiple alternatively spliced isoforms of TRIC in various tissues and that mutations of TRIC associated with hearing loss remove all or most of a conserved region in the cytosolic domain that binds to the cytosolic scaffolding protein ZO-1. A wild-type isoform of tricellulin, which lacks this conserved region, is unaffected by the mutant alleles and is hypothesized to be sufficient for structural and functional integrity of epithelial barriers outside the inner ear.     

Effect of Deficiency of Dietary Nitrogen on Cellulose Digestibility and Nitrogen-Fixing Flora Activity in Sibling Vole Microtus rossiaemeridionalis

The effect of feed composition on nitrogen-fixing activity of the symbionts living in the digestive tract of sibling vole Microtus rossiaemeridionalis was experimentally studied. In the control, the rodents were allowed to select any of three feeds: protein-rich, protein-free with low cellulose content, and protein-free with high cellulose content. The voles consumed the food in a proportion corresponding to 16% of protein and about 6% of cellulose. Exclusion of the protein-rich food considerably increased cellulose consumption (up to 12%) and digestibility (from 35 to 64%). The changes in the consumed feed composition were reflected in localization of nitrogenase activity in the digestive tract: the control level of nitrogen-fixing activity in the cecum was three times that in the proventriculus, while an inverse proportion was observed in the experimental groups. In all cases, the colon was the major locus of nitrogen fixation.     

The Formation of Artificial Nitrogen-Fixing Symbioses with Rape (Brassica napusvar. napus) Plants in Nonsterile Soil

The treatment of rape plants grown in nonsterile soil with 2,4-dichlorophenoxyacetic acid (auxin-like growth-promoting substance) or their inoculation with the bacterial association Micrococcussp. + Rhodococcussp. and/or with the mixed nitrogen-fixing culture Azotobacter nigricans+ Bacillussp. led to the formation of paranodules on the rape roots. The introduced bacteria were detected both in the intercellular space and inside the cells of the paranodules and the rape roots. The nitrogen-fixing activity of the paranodulated plants was two times higher than that of the inoculated plants lacking paranodules and five times higher than that of the control (i.e., not inoculated) plants. The paranodulation led to a 40% increase in the crop yield of rape plants and provided for a statistically significant increase in the total nitrogen as well as protein nitrogen contents of the plants.     

Revisiting Kadenbach: Electron flux rate through cytochrome c‐oxidase determines the ATP‐inhibitory effect and subsequent production of ROS

Mitochondrial respiration is the predominant source of ATP. Excessive rates of electron transport cause a higher production of harmful reactive oxygen species (ROS). There are two regulatory mechanisms known. The first, according to Mitchel, is dependent on the mitochondrial membrane potential that drives ATP synthase for ATP production, and the second, the Kadenbach mechanism, is focussed on the binding of ATP to Cytochrome c Oxidase (CytOx) at high ATP/ADP ratios, which results in an allosteric conformational change to CytOx, causing inhibition. In times of stress, ATP‐dependent inhibition is switched off and the activity of CytOx is exclusively determined by the membrane potential, leading to an increase in ROS production. The second mechanism for respiratory control depends on the quantity of electron transfer to the Heme aa3 of CytOx. When ATP is bound to CytOx the enzyme is inhibited, and ROS formation is decreased, although the mitochondrial membrane potential is increased.     

Investigation of karyotypic composition and evolution in <Emphasis Type="Italic">Lilium</Emphasis> species belonging to the section martagon

Analyzing chromosomal traits is one of the pragmatic ways to establish evolutionary and genetic database of plants that has complicated phylogenetic system. There are some conflicts on the exact phylogeny and evolutionary pathway of Lilium, and section martagon is the most complicated part among them. In this study, chromosomal traits of martagon lily species are described. All martagon lilies were analyzed with FISH (Fluorescence in situ hybridization) technique, followed by detailed karyotyping. Each species showed 2n = 2x = 24 of chromosome complement. Size of chromosomes ranged from 451.04 to 680.06 µm. 5S and 45S ribosomal DNA, general molecular markers in modern evolutionary research were used as probe in this study. Variation in rDNA loci and chromosome translocation were observed in Lilium hansonii; the highest number of 45S rDNA loci was detected in Lilium hansonii, followed by other martagon lilies, in similar locations but with differences, and chromosome translocation was observed from one individual of Lilium hansonii. Additionally, Lilium tsingtauense from Jeju-do Island, Korea was detected with two extra chromosomes. These kind of genetic variations through karyotyping indicate ongoing genetic variations in martagon lilies. In this study, precise analysis of chromosome traits in Lilium species belonging to section martagonperformed to contribute to better comprehension of the evolutionary pathway and establishment of cytogenetic database for further plant breeding research.