In the Universe, oxygen is the third most widespread element, while on Earth it is the most abundant one. Moreover, oxygen is a major constituent of all biopolymers fundamental to living organisms. Besides O 2 , reactive oxygen species (ROS), among them hydrogen peroxide (H 2 O 2 ), are also important reactants in the present aerobic metabolism. According to a widely accepted hypothesis, aerobic metabolism and many other reactions/pathways involving O 2 appeared after the evolution of oxygenic photosynthesis. In this study, the hypothesis was formulated that the Last Universal Common Ancestor (LUCA) was at least able to tolerate O 2 and detoxify ROS in a primordial environment. A comparative analysis was carried out of a number of the O 2 -and H 2 O 2 -involving metabolic reactions that occur in strict anaerobes, facultative anaerobes, and aerobes. The results indicate that the most likely LUCA possessed O 2 -and H 2 O 2 -involving pathways, mainly reactions to remove ROS, and had, at least in part, the components of aerobic respiration. Based on this, the presence of a low, but significant, quantity of H 2 O 2 and O 2 should be taken into account in theoretical models of the early Archean atmosphere and oceans and the evolution of life. It is suggested that the early metabolism involving O 2 /H 2 O 2 was a key adaptation of LUCA to already existing weakly oxic zones in Earth's primordial environment.

Artemisia vulgaris L. (common mugwort) is a species with great importance in the history of medicine and was called the “mother of herbs” in the Middle Ages. It is a common herbaceous plant that exhibits high morphological and phytochemical variability depending on the location where it occurs. This species is well known almost all over the world. Its herb—Artemisiae vulgaris herba—is used as a raw material due to the presence of essential oil, flavonoids, and sesquiterpenoids lactones and their associated biological activities. The European Pharmacopoeia has listed this species as a potential homeopathic raw material. Moreover, this species has been used in traditional Chinese, Hindu, and European medicine to regulate the functioning of the gastrointestinal system and treat various gynecological diseases. The general aim of this review was to analyze the progress of phytochemical and pharmacological as well as professional scientific studies focusing on A. vulgaris. Thus far, numerous authors have confirmed the beneficial properties of A. vulgaris herb extracts, including their antioxidant, hepatoprotective, antispasmolytic, antinociceptive, estrogenic, cytotoxic, antibacterial, and antifungal effects. In addition, several works have reviewed the use of this species in the production of cosmetics and its role as a valuable spice in the food industry. Furthermore, biotechnological micropropagation of A. vulgaris has been analyzed.

It is widely accepted that cyanobacteria-dependent oxygen that was released into Earth's atmosphere ca. 2.5 billion years ago sparked the evolution of the aerobic metabolism and the antioxidant system. In modern aerobes, enzymes such as superoxide dismutases (SODs), peroxiredoxins (PXs), and catalases (CATs) constitute the core of the enzymatic antioxidant system (EAS) directed against reactive oxygen species (ROS). In many anaerobic prokaryotes, the superoxide reductases (SORs) have been identified as the main force in counteracting ROS toxicity. We found that 93% of the analyzed strict anaerobes possess at least one antioxidant enzyme, and 50% have a functional EAS, that is, consisting of at least two antioxidant enzymes: one for superoxide anion radical detoxification and another for hydrogen peroxide decomposition. The results presented here suggest that the last universal common ancestor (LUCA) was not a strict anaerobe. O 2 could have been available for the first microorganisms before oxygenic photosynthesis evolved, however, from the intrinsic activity of EAS, not solely from abiotic sources.

The study used Actinidia deliciosa endosperm-derived callus to investigate aspects of the morphology, histology and chemistry of extracellular matrix (ECM) structures in morphogenically stable tissue from long-term culture. SEM showed ECM as a membranous layer or reticulated fibrillar and granular structure linking the peripheral cells of callus domains. TEM confirmed that ECM is a distinct heterogeneous layer, up to 4 mum thick and consisting of amorphous dark-staining material, osmiophilic granules and reticulated fibres present outside the outer callus cell wall. ECM covered the surface of cells forming morphogenic domains and was reduced during organ growth. This structure may be linked to acquisition of morphogenic competence and thus may serve as a structural marker of it in endosperm-derived callus. ECM was also observed on senescent cells in contact with the morphogenic area. Treatment of living calluses with chloroform and washing with ether-methanol led to partial destruction of the extracellular layer. Digestion with pectinase removed the membranous layer almost completely and exposed thick fibrillar strands and granular remnants. Digestion with protease did not visibly affect the surface layer. Indirect immunofluorescence showed low-methylesterified pectic epitopes labelled by JIM5 monoclonal antibody. Immunolabelling, histochemistry, and solvent and enzyme treatments suggested pectins and lipids as components of the surface layer. These compounds may indicate protective, water retention and/or cell communication functions for this external layer.

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