Photosynthetic and Respiratory Capacity of Foliose Lichen Lobaria pulmonaria throughout the Annual Cycle

Russian Journal of Plant Physiology - Lichens are unique phototrophic organisms whose physiology of stress tolerance attracts much attention. Parameters of photosynthetic and respiratory activities...     

Bud dormancy breaking affects respiration and energy balance of bilberry shoots in the initial stage of growth

Respiration and heat production in the shoots of bilberry (Vaccinium myrtillus L.) were studied at the beginning of growth after breaking bud dormancy by means of transfer of the shoots to indoor conditions (November–April) and upon natural sprouting in spring (May). The buds released from dormancy at the beginning of winter sprouted slower and showed lower respiratory activity than the buds that started growing in May. In May, cytochrome respiratory pathway in sprouting buds was 1.3 times more active than energetically ineffective alternative pathway, whereas activity of cytochrome pathway in December was 1.4 times lower as compared with the alternative. In November–December, the rate of heat evolution by the buds was 3–5 times lower than in April–May. In case of early breaking of bud dormancy, the share of respiration energy dissipated as heat was 30% on average. In the buds whose growth was induced later, the value of this parameter was twice as much. The ratio between heat evolution and respiration depended on temperature. High temperature more intensely activated heat evolution than respiration, which caused a decrease in the level of metabolic energy available for growth. In the temperature range of 5–15°C characteristic of the beginning of vegetation, the share of respiration energy dissipated as heat was 2–3 times lower than at 20–30°C, which reflects a great adaptability of V. myrtillus to climatic conditions of the region. Our data suggest that progression through a full cycle of winter dormancy is physiologically important for shoot growth. Early dormancy release brought about changes in respiration and energy balance of the shoots in the initial stage of extra-bud growth.     

Study of visual pigment rhodopsin supramolecular organization in photoreceptor membrane by small-angle neutron scattering method with contrast variation

Supramolecular organization of rhodopsin in the photoreceptor membrane was investigated by small-angle neutron scattering method. The experiments, which were performed with mixtures of heavy/light water as solvent (contrast variation method), were aimed at obtaining information about the lipid and protein components of the photoreceptor disc membrane separately. It was shown that the packaging density of the rhodopsin molecules in the photoreceptor membrane was unusually high: the distance between the centers of the molecules was approximately 56 Å. The probability of the monomeric state of rhodopsin molecules in the photoreceptor membrane, according to the data obtained, is rather high.     

Sugar Lego: gene composition of bacterial carbohydrate metabolism genomic loci

Background

Bacterial carbohydrate metabolism is extremely diverse, since carbohydrates serve as a major energy source and are involved in a variety of cellular processes. Bacterial genes belonging to same metabolic pathway are often co-localized in the chromosome, but it is not a strict rule. Gene co-localization in linked to co-evolution and co-regulation. This study focuses on a large-scale analysis of bacterial genomic loci related to the carbohydrate metabolism.

Results

We demonstrate that only 53% of 148,000 studied genes from over six hundred bacterial genomes are co-localized in bacterial genomes with other carbohydrate metabolism genes, which points to a significant role of singleton genes. Co-localized genes form cassettes, ranging in size from two to fifteen genes. Two major factors influencing the cassette-forming tendency are gene function and bacterial phylogeny. We have obtained a comprehensive picture of co-localization preferences of genes for nineteen major carbohydrate metabolism functional classes, over two hundred gene orthologous clusters, and thirty bacterial classes, and characterized the cassette variety in size and content among different species, highlighting a significant role of short cassettes. The preference towards co-localization of carbohydrate metabolism genes varies between 40 and 76% for bacterial taxa. Analysis of frequently co-localized genes yielded forty-five significant pairwise links between genes belonging to different functional classes. The number of such links per class range from zero to eight, demonstrating varying preferences of respective genes towards a specific chromosomal neighborhood. Genes from eleven functional classes tend to co-localize with genes from the same class, indicating an important role of clustering of genes with similar functions. At that, in most cases such co-localization does not originate from local duplication events.

Conclusions

Overall, we describe a complex web formed by evolutionary relationships of bacterial carbohydrate metabolism genes, manifested as co-localization patterns.

Reviewers

This article was reviewed by Daria V. Dibrova (A.N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia), nominated by Armen Mulkidjanian (University of Osnabrück, Germany), Igor Rogozin (NCBI, NLM, NIH, USA) and Yuri Wolf (NCBI, NLM, NIH, USA).

     

Ontogenetic aspects of plant respiration (by the example of <Emphasis Type="Italic">Rubus chamaemorus</Emphasis> L.)

Respiration, content of soluble carbohydrates and phenolics, level of lipid peroxidation, and activity of peroxidase and polyphenoloxidase were investigated in the leaves of cloudberry (Rubus chamaemorus L.) in different stages of shoot development. Age dependence of respiration was wave like with peaks associated with the periods of vegetative growth and fruit bearing. Prior to the onset of fruit bearing, respiration was clearly suppressed, while the content of soluble carbohydrates rose. In the course of development, contribution of cytochrome pathway to total respiration changed more drastically than participation of energy-wise ineffective alternative pathway. Activation of residual (nonmitochondrial) respiration observed in the postgenerative period directly correlated with a rise in activity of polyphenoloxidase and peroxidase in the leaves. The results show that ontogenetic changes in leaf respiration are complex and depend on genetically predetermined processes of plant growth and development. Behavior of respiration and its components predictably reflects changes in the direction and intensity of overall metabolism of plants associated with strict order of alternation of regular age states.     

Activities of respiratory pathways and the pool of nonstructural carbohydrates in greening leaves of spring wheat seedlings

Seedlings of spring wheat (Triticum aestivum L.) were used to study the dynamics of leaf respiration, the respiratory pathway ratio, and relation of activities of these pathways to the content of soluble carbohydrates in the leaf during greening of seedlings for 48 h under continuous photosynthetically active light (190 μmol/(m² s)). Changes in leaf respiration during de-etiolation were closely related to modulation of the alternative respiratory pathway (AP) activity. The rate of cytochrome respiratory pathway (CP) depended directly on the carbohydrate content and growth rate. These relations suggest that the substrate regulation of CP activity during greening is mediated by the energy needs for growth and is effectively regulated by the mechanism of respiratory control. The highest rates of AP were observed after a 6-h exposure of seedlings to light. The proportion of CP/AP at this stage was close to unity. The temporal pattern of AP activity during de-etiolation was independent on the content of soluble carbohydrates. Hence, in addition to substrate regulation of AP, there are other intricate mechanisms of AP involvement. Our results are in accordance to the state that the alternative respiratory pathway participates in maintaining homeostasis in phototrophic cells during development of the photosynthetic function.