Timiryazev Institute of Plant Physiology

Decades ago, the introduction of GC-MS marked a significant advancement in primary plant metabolite studies. Here, in our review, we will delve into critical aspects of the workflow, spanning the selection of an analytical platform, sample preparation, analytical acquisition, and data processing and interpretation. The exceptional separation capabilities of GC, characterized by remarkable chromatographic resolution, render it ideal for analysis of the complex plant metabolome, including the separation of isomeric compounds. The diversity of analytical platforms allows the investigation of plant metabolomes using targeted and non-targeted approaches. GC-MS, equipped with efficient extraction methods and reliable derivatization protocols for semi- and non-volatile compounds, enables qualitative and quantitative analysis of these molecules. The stability of derivatives forms the foundation for the robustness and reproducibility of GC-MS methods, and their mass spectra provide characteristic fragments for confident identification and sensitive quantification of individual metabolites. There has been key progress in the advancement of GC-MS approaches to studying plant metabolism. However, the presence of artifacts during GC-MS analysis, particularly during derivatization, is a challenge that requires careful validations, which frequently necessitate additional investigations. The feasible solutions that were achieved to overcome the limitations in GC-MS-based studies are a particular focus of the present discussion.

Manganese (Mn) is a crucial micronutrient for plants. The impaired function of the oxygen-evolving complex in Photosystem II (PSII) due to Mn deficiency is believed to result in the overproduction of reactive oxygen species and the induction of an enzymatic antioxidant system. In our study, we investigated the effects of progressive Mn deficiency (the difference in Mn content between the needles of control and Mn-deficient plants increased from 17-fold at the beginning of the experiment to 59-fold at the end) on the activities of superoxide dismutase (SOD), catalase, ascorbate peroxidase, and guaiacol peroxidase in the roots and needles of Scots pine seedlings. We found that the soluble protein content in plant organs under Mn deficiency was maintained at a level comparable to that of the control. Regardless of the severity of Mn deficiency, the needles of the Mn-deficient plants presented twofold lower SOD activity than the needles of the control plants. These differences were observed even when Mn deficiency did not negatively affect plant growth. Additionally, the total SOD activity in the needles of both plant groups was determined solely by the activity of the Cu/Zn-containing SOD isozymes. Compared with the control plants, Mn deficiency did not result in an increase in any of the studied H2O2-degrading enzymes in the needles of the seedlings. In contrast, the needles of the Mn-deficient plants presented a lower level of guaiacol peroxidase activity. Despite the inhibition of root growth, Mn deficiency led to changes in the balance of the enzymatic antioxidant system in plant roots. The data obtained suggest that the lack of activation of SOD and other antioxidant enzymes in Scots pine seedlings against the background of progressive Mn deficiency is due to the reduced ability of PSII to generate ROS under these conditions.

The International Conference on “Photosynthesis and Hydrogen Energy Research” was inaugurated in 2004 in Trois Rivières, Canada, as “Photosynthesis and Post-Genomics Era”. It was conceived by its founders, Suleyman I. Allakhverdiev (Russia), Vyacheslav (Slava) Klimov (Russia), Robert Carpentier (Canada), and Prasanna Mohanty (India) to be an alternating conference to the bigger International Congress on Photosynthesis, which was then held every three years. The name was changed to the International Conference on Photosynthesis (ICP) in 2011. In 2013, “Hydrogen Production” was added, and then finally the current name, “International Conference on Photosynthesis and Hydrogen Energy Research for Sustainability”, was used in 2015. The conferences over the last twenty years have been held in three continents – North America, Europe, and Asia – and have been very successful in attracting participants with the latest ideas in photosynthesis, hydrogen production, and energy sustainability. Here we describe all 12 conferences, with details of the major events of each conference.Major points of the conference were: (1) Recent advances in the understanding of the basic mechanisms of water splitting (photosystem II) and the reactions around photosystem I in photosynthetic organisms. (2) The role of hydrogen production in photosynthesis. (3) The role of innovations in photosynthesis and hydrogen production in the development of global sustainability.

The influence of crown illumination on leaf damage of horse chestnut species (Aesculus hippocastanum L., Aesculus glabra Willd, Aesculus flava Aiton, Aesculus pavia L., Aesculus × carnea Hayne, Aesculus parviflora Walter, Aesculus chinensis Bunge) affected by ohrid leaf miner (Cameraria ohridella Deschka & Dymić) was studied using some accessions from the arboretum botanical tree collection. A. hippocastanum, A. glabra, A. flava had the lowest chl a content in the foliage on the sunlit side of the crown, while in A. pavia, A. parviflora and A. chinensis this indicator was the highest. The chl a content in the leaves of A. hippocastanum and A. flava under shaded conditions was 1.3 and 2.4 times higher than in the sunlit part, while in A. pavia, A. parviflora and A. chinensis the chl a content on the shaded side was 1.2, 1.6 and 1.3 times lower. The quantitative content of chl b in the sunlit part of the crown in A. hippocastanum and A. flava was significantly higher than in the other species. Moreover, while A. flava and A. parviflora had the highest chl b content in the foliage of the shaded part of the crown, A. glabra and A. × carnea had the lowest. Similarly, differences in proline levels were found in the leaves of different horse chestnut species on the sunny side of the crown. Higher proline levels in less infested species were identified. Water content imbalances due to feeding by leaf miners were most characteristic of the severely affected species. Chlorophyll fluorescence determination revealed high photochemical activity with an effective defense system in resistant species, while non-resistant species exhibited weak defense mechanisms in both sunlight and shade. To assess horse chestnut species the hyperspectral analysis indices (DSWI and SIPI) were also successfully applied. Changes in chl a and chl b content, proline levels, and leaf water-holding properties can be used to assess the resistance of horse chestnut species using classical physiological and biochemical methods. Hyperspectral analysis indices (DSWI and SIPI) can also be successfully applied.

Species Pseudomonas brassicacearum was described both as plant growth-promoting (PGP) rhizobacterium and necrotrophic opportunistic phytopathogen. An important PGP property of this rhizobacterium is the activity of 1-aminocyclopropane-1-carboxylate (ACC) deaminase, which reduces abiotic stress in plants. Tomatoes are an important but drought-sensitive agricultural crop. Growth and physiological and biochemical responses of well-watered and water-limited tomatoes to such kind of rhizobacteria were addressed using Ps. brassicacearum Am3 or its ACC deaminase deficient mutant T8-1. The counts of the introduced P. brassicacearum Am3 and T8-1 in the tomato rhizosphere at the end of experiment were similar under both water regimes. The applied drought and inoculations did not yield differences in the content of water, chlorophyll, indole-3-acetic and indole-3-lactic acids in leaves. Drought reduced stomatal conductance and inhibited shoot growth, whereas only wild type Am3 maintained shoot biomass on the level of well-watered plants. Strain Am3 lowered difference in the contents of thiobarbithuric acid reactive substances (expressed as malondialdehyde equivalents) between well-watered and droughted plants. This strain also decreased abscisic acid content in roots, as well as hydrogen peroxide, salicylic and indole-carboxylic acid contents in leaves of water-limited plants. The mutant T8-1 decreased content of abscisic and indole-3-lactic acids in roots and abscisic and indole-3-carboxylic acids in leaves of water-limited plants. Thus, under water-limitation Ps. brassicacearum Am3 having high ACC deaminase activity exhibited the properties of PGPR and stimulated plant growth, but the deficiency of ACC deaminase in T8-1 redirected the action of bacteria towards saprophytic or even deleterious effects.

The positional distribution of fatty acids (FAs) in Vischeria punctata strain IPPAS H-242 during nitrogen starvation was analysed, and 22 individual FAs were identified in total lipids, TAGs, and native sn-1,2-diacylglycerols, comprising both saturated and polyunsaturated FAs. The predominant FAs were 14:0, 16:0, 16:1n-7, 18:1n-9, and 20:5n-3, accounting for more than 98.5% of the total FAs. TAGs demonstrated unique regioselectivity, with stearic, oleic, and eicosapentaenoic acids acylating the molecules at sn-1 and sn-3 positions. Instead, the sn-2 position was acylated with myristic, palmitic (8.4% and 40.1%, respectively) and palmitoleic (50.6%) acids, resulting in a total contribution of 99.1% from these three FAs. Palmitic, palmitoleic, and oleic acids made up 7.5, 73.9, and 13.1% of the sn-1(3) positions, respectively, or 94.5% in total. The molecular types of TAGs that accumulated in the cells of the microalga Vischeria punctata were as follows: UUU, 41.3%, and USU, 39.2%; TAGs of the UUS and USS types accounted for 9.4% and 9.0%, respectively. Tripalmitoleoyl-triacylglycerol, sn-1,3-dipalmitoleoyl-2-palmitoyl-glycerol, rac-1-oleoyl-2,3-dipalmitoleoyl-glycerol, and rac-1-oleoyl-2-palmitoyl-3-palmitoleoyl-glycerol were found as the most common molecular species of TAGs. Thus, Vischeria punctata strain IPPAS H-242 may be considered as a potential producer of structured TAGs with palmitic acid at the sn-2 position and palmitoleic acid at the sn-1 and sn-3 positions. The subsequent hydrolysis of such TAGs by pancreatic lipase produces palmitoleic acid and sn-2-palmitoylglycerol that have significant nutraceutical value and serve as a source of digestible palmitic acid for infant nutrition.

Moderate concentrations of Na+ ions in the growth medium have positive effects on growth and performance characteristics of the C4 euhalophyte Suaeda altissima, optimizing functioning of both, stomata and photosynthetic apparatus. Effects of salinity on the morphology, ion relations, and gas exchange of the leaves in the euhalophyte Suaeda altissima (L.) Pall. were investigated with emphasis on the guard and epidermal cells. The presence of NaCl in the nutrient solution (NS) at both growth-stimulating (250mM) and growth-inhibiting (750mM) concentrations resulted in increased leaf succulence, net photosynthetic rate (Pn), and instantaneous water use efficiency (WUEi), and reduced stomatal conductance (gs), stomatal density on the leaf surface, and transpiration rate (E). X-ray microanalyses revealed Na and Cl accumulation in the guard and epidermal cells of leaves under salinity conditions. However, Na and Cl contents differed by not much in plants grown at 250 and 750mM NaCl, indicating a mechanism preventing accumulation of Na+ and Cl- ions in cells paving leaf surface at high NaCl concentrations. Examination of gs and E as functions of CO2 concentration in the leaf gas exchange chamber revealed better ability to regulate these parameters in 250mM NaCl-grown plants than in 750mM NaCl-grown or control plants. The study of Pn dependent on CO2 concentration in leaf intercellular space revealed direct stimulating effect of NaCl on photosynthesis. We hypothesize that S. altissima, a species having anatomy and ultrastructure features of C4 plants, improves its performance characteristics under saline conditions, optimizing not only the functioning of the stomata complex but also the process of CO2 assimilation, including the C4 fixation pathway.