Halina Ślesak

Oxygen and Hydrogen Peroxide in the Early Evolution of Life on Earth: In silico Comparative Analysis of Biochemical Pathways

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 Earths primordial environment.

Exogenous carbohydrate utilisation by explants of Brassica napus cultured in vitro

The influence of carbohydrate type (sucrose, maltose, glucose and fructose) used as carbon source in the medium on particular carbohydrates content in hypocotyls of Brassica napus cv. Topas during in vitro culture was studied. The variability in sugar composition in the explants depending on carbon source in the medium and duration of culture was found. The type of sugar did not influence the growth of cultured tissues during the first 15–20 days of culture. Sugars in the medium were main source of substrates for sucrose synthesis in growing explants. Significant re-synthesis of sucrose in the hypocotyls after the uptake of hexoses was found. Maltose was detected only in traces in tissues cultured on media devoid of this sugar. In the case of glucose and fructose, medium was the main source of these monosaccharides for tissues. In explants cultured on maltose-based medium, glucose content was lower comparing to hypocotyls cultured on sucrose medium. The highest fresh weight (FW) was noticed on the media supplied with sucrose and glucose. Changes in sugar content in culture media were also studied. Autoclaving hydrolysed ∼7% of the initial sucrose into glucose and fructose. The most distinct changes were noticed in the media supplied with sucrose and maltose. Glucose- and fructose-based media remained stable during whole period of culture.

Are extracellular matrix surface network components involved in signalling and protective function

Endosperm is an interesting model for in vitro experiments, because of its unique origin, development and ploidy level. Here we used Actinidia deliciosa endosperm-derived callus to investigate morphology, histology and chemistry of extracellular matrix (ECM) structures in morphogenically stable tissue from long - term culture. SEM and TEM analysis showed that ECM is a heterogenous layer which consists of amorphous, dark – staining material, osmiophilic granules and reticulated fibres outside the outer callus cell wall. This structure may serve as a structural marker of morphogenic competence in endosperm – derived callus, because of its presence on the surface of callus forming morphogenic domains and its disappearance during organ growth. Based on immunolabelling, histochemistry, solvent and enzyme treatments, we suggest that pectins and lipids are components of the ECM layer. These results might indicate protective, water retention and/or cell communication functions for this ECM layer. Addendum to: Popielarska-Konieczna M, Kozieradzka-Kiszkurno M, Świerczyńska J, Góralski G, Ślesak H, Bohdanowicz J. Ultrastructure and histochemical analysis of extracellular matrix surface network in kiwifruit endosperm-derived callus culture. Plant Cell Rep 2008; 27:1137-45.

The effect of genotype on a barley scutella culture. Histological aspects

Cereals are known to be recalcitrant to the induction of morphogenesis in vitro and the majority of the methods used are callus-mediated and species/genotype-dependent. In the present investigation, a method of morphogenesis induction from immature scutella of selected barley cultivars was used, and particular attention was paid to histology in the initial stages of the regeneration process in order to confirm whether it occurs directly or indirectly (via callus formation). The length of the period from inoculating scutella on the medium to obtaining plantlets depended on the cultivar and the individual scutellum of the barley and varied between 2.5–4 months. The regeneration efficiency and viability of barley scutella was revealed to be highly genotype dependent. The average number of regenerated plants per regenerating scutellum was highest in the case of cv Granal (3.7). A histological analysis of the cultured explants showed both non-morphogenic and morphogenic callus formation. Two types of indirect morphogenetic response were observed: organogenesis (shoot bud formation) and somatic embryogenesis. This is the first report concerning an analysis of in vitro regeneration from immature scutella of barley cultivars (Stratus, Ryton, Granal and Binal).

Orobanche grenieri (Orobanchaceae), a Southwestern European Species Newly Found in Asia

We report occurrences of Orobanche grenieri (Orobanchaceae) in the Lesser Caucasus in southern Georgia (western Asia), and in Badakhshan in Tajikistan (central Asia). These localities are more than 3000 and 5000 km apart from its previously known distribution areas in Spain and France, respectively. We used morphological evidence as well as nuclear ribosomal ITS and plastid rbcL sequences to test the taxonomic assignment of the Georgian plants to O. grenieri and to determine their phylogenetic position. We list the features that differentiate O. grenieri from morphologically similar species, provide illustrations, a distribution map, and we propose an IUCN conservation status for the Georgian populations.

RubisCO early oxygenase activity : a kinetic and evolutionary perspective

RubisCO (D‐ribulose 1,5‐bisphosphate carboxylase/oxygenase) is Earths main enzyme responsible for CO2 fixation via carboxylation of ribulose‐1,5‐bisphosphate (RuBP) into organic matter. Besides the carboxylation reaction, RubisCO also catalyzes the oxygenation of RuBP by O2, which is probably as old as its carboxylation properties. Based on molecular phylogeny, the occurrence of the reactive oxygen species (ROS)‐removing system and kinetic properties of different RubisCO forms, we postulated that RubisCO oxygenase activity appeared in local microoxic areas, yet before the appearance of oxygenic photosynthesis. Here, in reviewing the literature, we present a novel hypothesis: the RubisCO early oxygenase activity hypothesis. This hypothesis may be compared with the exaptation hypothesis, according to which latent RubisCO oxygenase properties emerged later during the oxygenation of the Earths atmosphere. The reconstruction of ancestral RubisCO forms using ancestral sequence reconstruction (ASR) techniques, as a promising way for testing of RubisCO early oxygenase activity hypothesis, is presented.