Metabolomic and physiological changes of <Emphasis Type="Italic">Chlamydomonas reinhardtii</Emphasis> (Chlorophyceae,Chlorophyta) during batch culture development

During mixotrophic batch culturing, the microalga Chlamydomonas reinhardtii goes through S-shaped growth kinetics and cells consistently transit from division to death. Photosynthesis and respiration had two simultaneous maxima at the first half of the exponential growth phase and at the border of the stationary phase. GC-MS analysis detected about 300 compounds of which about 100 were identified. Differences in metabolite profiles were observed between cells sampled at different time points of the growth curve. Several data mining methods clearly indicated that metabolomes tended to group together in a time-dependent manner. Clustering analysis revealed three major groups of metabolites varied in concentration dynamic. The alterations in lipophilic compounds and carbohydrates took place even within the same phase of culture growth, which indicated complex rearrangements in cell biochemistry and physiology. Special attention was paid to alterations in the ratios between metabolite groups. The most significant ratio changes were discovered for pools of amino and fatty acids.     

Description of the Photosynthetic Apparatus of <Emphasis Type="Italic">Fucus vesiculosus</Emphasis> L. in Early Embryogenesis

Dynamics of some photosynthetic parameters was studied in gametes, zygotes, and embryos of kelp Fucus vesiculosus L. The following indices were determined at different stages of seaweed early development: the contents of pigments and ribulose-1,5-bisphosphate carboxylase/oxygenase, the rates of photosynthesis and dark respiration, and the activities of photosystems I and II. The dynamics of photosynthetic activity in the zygotes and embryos of F. vesiculosus proved to reflect the main physiological processes of its early development.     

Compensation for the absence of the catalytically active half of DNA polymerase ε in yeast by positively selected mutations in CDC28

Current eukaryotic replication models postulate that leading and lagging DNA strands are replicated predominantly by dedicated DNA polymerases. The catalytic subunit of the leading strand DNA polymerase ε, Pol2, consists of two halves made of two different ancestral B-family DNA polymerases. Counterintuitively, the catalytically active N-terminal half is dispensable, while the inactive C-terminal part is required for viability. Despite extensive studies of yeast Saccharomyces cerevisiae strains lacking the active N-terminal half, it is still unclear how these strains survive and recover. We designed a robust method for constructing mutants with only the C-terminal part of Pol2. Strains without the active polymerase part show severe growth defects, sensitivity to replication inhibitors, chromosomal instability, and elevated spontaneous mutagenesis. Intriguingly, the slow-growing mutant strains rapidly accumulate fast-growing clones. Analysis of genomic DNA sequences of these clones revealed that the adaptation to the loss of the catalytic N-terminal part of Pol2 occurs by a positive selection of mutants with improved growth. Elevated mutation rates help generate sufficient numbers of these variants. Single nucleotide changes in the cell cycle-dependent kinase gene, CDC28, improve the growth of strains lacking the N-terminal part of Pol2, and rescue their sensitivity to replication inhibitors and, in parallel, lower mutation rates. Our study predicts that changes in mammalian homologs of cyclin-dependent kinases may contribute to cellular responses to the leading strand polymerase defects.     

Influence of phytohormones on morphology and chlorophyll a fluorescence parameters in embryos of Fucus vesiculosus L. (Phaeophyceae)

While a variety of plant hormones from brown algae were described, there were few studies that examined the combined effects of these hormones on morphogenesis and photosynthetic physiology in developing fucoid embryos. We evaluated the effects of phytohormones to determine the extent, to which responses were similar to those of terrestrial plants. Kinetin, IAA, ABA, GA₃, and kinetin + IAA were added to seawater at a physiological concentration (1 mg/L), and embryos of Fucus vesiculosus L. were grown for 10 days. Photosynthetic activity of single embryos or embryo cells were characterized using the following fluorescence parameters: minimum fluorescence yield (F ₀), maximum quantum yield (F _v/F _m), relative maximum rate of electron transfer to photosystem II under saturation irradiances (rETR_max), photosynthetic efficiency under non-saturating irradiances (αETR) and saturation irradiance (E _k). In addition, embryo length and diameter and apical hair length and number were determined. Morphological changes associated with hormone treatments included an increase in the embryo length in the presence of IAA, an increase in the embryo diameter in the presence of IAA, kinetin, and kinetin + IAA, an increase in the maximum hair length and number in the presence of kinetin + IAA, and a decrease in the hair length and number in the presence of ABA. With respect to fluorescence parameters, significant effects of phytohormones included an increase in the F ₀ and F _v/F _m at kinetin treatment, a synergistic effect of kinetin + IAA on F _v/F _m, rETR_max, and αETR, a promotion of F _v/F _m by GA, and a decrease of the parameters by ABA. These results are consistent with the data on responses of land plants to the same hormones and suggest that brown algae have evolved regulatory mechanisms for morphogenesis and photosynthetic regulation similar to plants.     

Mechanisms of bioadhesion of macrophytic algae

During the evolution the benthic macrophytic algae developed effective mechanisms of bioadhesion enabling their attachment to almost any surface in the aqueous medium. The attachment of algal spores and zygotes includes two successive stages: the primary and the secondary (final) adhesion. Analysis of information on the composition of adhesive materials and attachment mechanisms in brown, green, and red marine macrophytes indicates that synthesis and release of adhesive substances by algal cells can be considered as a temporary intensification of cell wall synthesis. The structure of the primary adhesive material comprises a gel phase (alginate, ulvan, and agar gels) and a structuring component, i.e., a flexible network based on branched chains and/or rings of phenolic compounds, polysaccharides, or glycoproteins. Irreversible hardening of the primary adhesive material arises from phenol polymerization catalyzed by different peroxidases (brown algae) or from polymerization of glycoproteins comprising amino acids with phenolic residues (red algae). In parallel with these processes, covalent cross-links are being formed between the adhesive structural components and the gel phase polysaccharides. This results in the formation of the secondary adhesive and in eventual attachment of the organism to the substrate. The attachment mechanisms of benthic algae appear to have some features in common with the mechanisms of bioadhesion of marine invertebrates.     

Concise review of the genus Vertebrata S.F. Gray (Rhodophyta: Ceramiales)

Journal of Applied Phycology - The red algal genus Vertebrata (Ceramiales, Rhodophyta) comprises 30 species of rather small filamentous algae, differing in morphology, distribution, and ecological...     

Role of Auxin in Induction of Polarity in Fucus vesiculosus Zygotes

We studied the effects of auxin (indole-3-acetic acid) on formation of the primary polarity axis in zygotes of the brown algae Fucus vesiculosusL. Within the first 2.5 h after fertilization, the zygotes release this phytohormone in the ambient medium. The treatment of developing zygotes with the inhibitor of indole-3-acetic acid transport from the cell 2,3,5-triiodobenzoic acid at 5 mg/l arrests the auxin secretion and leads to its accumulation in the cells. This causes a significant delay in zygote polarization. The treatment of zygotes with the exogenous indole-3-acetic acid at 1 mg/l stimulates cell polarization and formation of a rhizoid protuberance. When auxin was added to the medium with triiodobenzoic acid, the inhibitory effect of the latter was eliminated. It has been proposed that the content of indole-3-acetic acid in the ambient medium is a key factor in the induction of polarity of the F. vesiculosus zygotes.     

Phytohormones in algae

In various algal taxa, essentially all known phytohormones were detected in concentrations comparable with their content in higher plants. The occurrence of diverse free and conjugated hormone forms substantiates the functioning of the complex system of metabolism and activity regulation of these compounds. In most cases, the spectrum of biological activities of algal hormones corresponds to the functions of higher plant hormones. Some physiological and biochemical processes in algal cells and tissues are under the control of several phytohormones. All these facts permit a consideration of the algal hormonal system as a full-value regulatory system.