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Intricate, dynamic, and absolutely unavoidable ageing affects cells and organisms through their entire lifetime. Driven by diverse mechanisms all leading to compromised cellular functions and finally to death, this process is a challenge for researchers. The molecular mechanisms, the general rules that it follows, and the complex interplay at a molecular and cellular level are yet little understood. Here, we present our results showing a connection between the linker histones, the higher-order chromatin structures, and the process of chronological lifespan of yeast cells. By deleting the gene for the linker histone in Saccharomyces cerevisiae we have created a model for studying the role of chromatin structures mainly at its most elusive and so far barely understood higher-order levels of compaction in the processes of yeast chronological lifespan. The mutant cells demonstrated controversial features showing slower growth than the wild type combined with better survival during the whole process. The analysis of the global chromatin organization during different time points demonstrated certain loss of the upper levels of chromatin compaction in the cells without linker histone. The results underlay the importance of this histone for the maintenance of the chromatin loop structures during ageing.

SummaryThe leaf epidermis structure of six Crataegus species from Bulgaria has been studied by light and scanning electron microscopy. Cyclocytic stomatal type, different types of simple single trichomes, cuticle ornamentation and waxes are determined. The results allow clear delimitation and identification of the species. Some conjectures about the relationships on inter-and intrageneric level and references of epidermal structure with adaptation to various ecological conditions are discussed.

Bioactive substances that are found in many natural plant extracts are very important for the cosmetics, pharmaceutical industry and biotechnology. Especially interesting for these industries are the substances that possess cell revitalizing and anti-ageing properties. The endemic plant Haberlea rhodopensis is known for its ability to withstand drought and to revitalize when returned to optimal conditions after a long time in desiccation. It is a mere fact that this plant not only can completely resurrect from a dried state but is also able to bring back the natural biochemical compositions of its cells. As a result H. rhodopensis offers a wide field for investigation of the exact mechanisms of the revitalization process as well as broadens the search for unique bioactive chemical substances in its cells. Here, by using the yeast Saccharomyces cerevisiae as a model we have demonstrated that methanol extracts from the plant H. rhodopensis hold specific properties to revitalize and ameliorate cellular growth as well as to balance intracellular metabolic states. Our results add valuable knowledge on the effects of natural compounds on ageing and reinforce the idea of using yeast as a model organism in the development of rapid tests for studying the efficacy of different bioactive substances.

Certain evidence has been collected about the imperative role of chromatin remodeling complexes (CRCs)

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