Vol 66, No 3 (2019)

In land plants, at least five groups of photoreceptors perceive information about light conditions and diurnal rhythm, as well as about ambient temperature, presence of pathogens or competing neighbors, direction of the gravity vector and other factors. The photoreceptor toolkit allows plants to integrate environmental information and “make decisions” necessary for survival and successful reproduction, i.e., whether to enter or exit dormancy, accelerate or stop growth, promote or delay flowering; choose the direction of growth, induce or suppress the formation of side shoots, as well as regulate the synthesis of volatile substances affecting the growth of neighbors or pathogens. These photoreceptors include phytochromes, cryptochromes, phototropins, the ZTL (ZEITLUPE) family proteins, and the ultraviolet-B receptor UVR8. In spite of the diversity of plants photoreceptors, their functionality follows several “common rules.” Transformation of the information on light quality and quantity into metabolic and morphogenetic responses occurs via controlled degradation of transcription factors mediated by interactions of the active form of a photoreceptor and the СОР1-SPA1 E3-ubiquitine ligase complex in the nucleus. Apart from interacting with СОР1, the active forms of photoreceptors in the nucleus can directly bind to transcription factors and trigger their degradation. Phytochromes belong to the largest (the molecular mass of a monomer is ca. 125 kD) and most sophisticated plant photoreceptors. In addition to the abovementioned mechanisms, they also regulate alternative splicing and the selection of alternative promoters for thousands of plant genes. The interaction of phytochrome with jasmonate signaling is of special interest, as phytochromes regulate the jasmonate-mediated cessation of growth in response to stress. This review focuses on data revealing the potential for the application of novel information on plant photoreceptors for the generation of crop varieties capable of high performance under stress conditions.

The peculiarities of the prevalence of C₄ species in the relief of the Kyzylkum Desert were revealed based on botanical and geographical descriptions. In the lowlands (0–50 m above sea level), a predominance of C₃ halophytes was found, while halophytes with C₄ photosynthesis began to predominate at medium elevations (50–200 m above sea level). Above 200 m above sea level, a sharp decline in the contribution of halophilic flora to the biodiversity of native vegetation was detected. Thus, the penetration of halophytes above 200 m is limited by the presence of C₄ photosynthesis as an adaptive characteristic to soil desalinization. A decrease in the succulence of leaf morphology in edificatory perennial plants of the Kyzylkum Desert (tamarix, saxaul, and camel thorn) was noted with a decrease in soil salinization. In the summer dry period, C₄ photosynthesis provides a competitive advantage over C₃ halophytes for survival on desalinated soils of elevated parts of the terrain desiccated during the summer. It was concluded that the acquisition of C₄ photosynthesis by halophilic species is an adaptation of the photosynthesis of halophilic flora to seasonal desalinization and drying of the soil of the elevated parts of the Kyzylkum Desert.

Leaf traits, the rate of gas exchange, and biomass were examined in five plurizonal species (Alisma plantago-aquatica L., Carex acuta L., Eleocharis palustris (L.) Roem. et Schult., Phalaris arundinacea L., and Typha angustifolia L.) of emergent plants growing in wetlands of forest (Middle Urals) and steppe (South Urals) zones. It was found that changes in the leaf thickness, leaf mass per area (LMA), the transpiration rate, and characteristics of the pigment complex associated with a rise in aridity were species-specific. Structural reorganization of the leaves of wetland plants growing in conditions of steppe wetland showed a general pattern of an increase in leaf density (1.2–2 times) and a reduction in leaf area (by 42–54%). This trend was accompanied by a reduction in the photosynthesis rate per 1 m² (1.2–3.4 times) or per 1 mg of chlorophyll (by 29–63%). In two species, P. arundinacea and T. angustifolia, we detected a decrease in stomatal conductance by 2 and 4.8 times, respectively, in more arid conditions. Analysis of interspecific relations between plant productivity and leaf parameters has shown that plant biomass positively correlated with leaf area (r = 0.84, P < 0.01) and with the photosynthesis rate per leaf area unit (r = 0.97, P < 0.001) both in the regions of the Middle and South Urals. On the whole, structural changes in the leaves associated with adaptation of plant water relations to semiarid climate lead to a decrease in photosynthetic activity of leaves and, therefore, a decline of plant height and productivity of emergent plants growing in steppe wetland.

Impact of relative air humidity (RAH) and watering mode on responses of cucumber (Cucumis sativus L.) plants to a daily short-term (2 h) temperature decrease to 10^oC (DROP treatment) was investigated. Plants were grown at comparably high (80%) or low (30%) RAH under conditions of normal watering or in the mode of artificially created “periodic drought.” It was found that RAH and watering mode exhibit strong quantitative and qualitative influence on plant responses to DROP treatment. Under high RAH, DROP treatment exhibits significant morphogenetic effect increasing plant biomass and compactness. Under the conditions of low RAH, effects of DROP treatment on plant compactness were leveled due to strong morphogenetic effect of the RAH itself and significant decrease in DROP-treated plant biomass under “drought”. Watering mode influenced on the effect of DROP treatment in a different manner depending on RAH. At high RAH, DROP treatment, together with “drought,” led to increase in plant compactness as well as their chilling tolerance. Besides, these plants became more tolerant to water stress induced by low temperature (4°C). At low RAH, no increase in compactness of DROP-treated plants was observed.

Water hyacinth (Eichhornia crassipes (Mart.) Solms), an invasive plant, is used to control algae-polluted water, but the mechanism among which is not clear. In this study, the allelopathic effects of water hyacinth on the growth of Microcytis aeruginosa were investigated. The physiological changes of M. aeruginosa such as chlorophyll content, superoxide dismutases (SODs), peroxidases (PODs), total protein contents (TPCs), and MDA contents were also determined. Our results showed that higher density of water hyacinth extracts and ethyl acetate fractions all showed significant allelopathic inhibition on the growth of M. aeruginosa. The ethyl acetate fraction considerably reduced the algae chlorophyll content. The higher concentration used of ethyl acetate fraction, the lower the chlorophyll content of algae. The activity of SODs and PODs were quite reduced after 10-day treatment by ethyl acetate fraction. The TPCs and MDA contents were also found to be decreased after 4-day treatment. It is inferred that water hyacinth inhibited the algal growth by released allelochemicals and affected diversity of biochemical and physiological attributes, and also lead to the membrane injury in the M. aeruginosa cells.

Soil salinity is a major constraint in crop production. Of the different strategies to cope with salt stress, a cross-tolerance strategy is inexpensive and easy to adopt. In this study, we investigated heat shock-induced salinity tolerance mechanism in lentil (Lens culinaris Medik cv. BARI Lentil-7). Six-day-old seedlings were exposed to 100 mM NaCl with or without 4-h heat shock (HS) (40 ± 1°C) for three days. The results showed that 100 mM NaCl reduced chlorophyll content, caused severe oxidative damage by reducing antioxidants, increased the toxic methylglyoxal (MG) content and disrupted ion homeostasis by increasing Na⁺ in the shoots and decreasing K⁺ in the roots. Heat shock pre-treatment improved the chlorophyll content and reduced oxidative damage by improving reduced ascorbate content, the GSH/GSSG ratio, catalase and ascorbate peroxidase activity under salt stress. Moreover, heat shock reduced the toxic MG content by upregulating glyoxalase system. Heat shock inhibited Na⁺ accumulation in the shoots and K⁺ efflux from the roots, as a result, the Na⁺/K⁺ ratio reduced both in the roots and shoots under salt stress. We further investigated the HS-induced changes in H₂O₂ and MG content. We assumed that the dynamics of H₂O₂ and MG at 1 h intervals during heat shock play a signaling role in activating antioxidant defense and glyoxalase pathway, as a result, plant showed tolerance to salt stress.

To explore proteomic characters of Kunitz-type trypsin inhibitors (KTIs) deleted soybean (Glycine max (L.) Merr.), seeds without KTIs and its female parent with KTIs were analyzed for differentially expressed proteins and specially expressed proteins using a label-free quantitative approach. A total of 1093 proteins were identified, with 139 up-regulated proteins among 169 differentially expressed proteins in both. Functional classification revealed that differentially expressed proteins were involved in almost functional categories, and carbohydrate metabolic process was the most abundant by enrichment analysis. Pathway analysis indicated that the differentially expressed proteins were mainly enriched into ribosome pathway, then carbohydrate metabolism. KTI3 (trypsin inhibitors A) interacted with β-conglycinin was independent from a complex protein network by proteins interactions analysis. Expression of KTI3 decreased in the seed of KTIs deleted soybean, which made for protein biosynthetic processes, metabolic processes and resistance processes. The specially expressed proteins analysis provided new information for the proteomic metabolism of KTIs deleted soybean resource during seed development, but it need further investigate for unknown information of KTIs deleted soybean.

Nanoparticles have entered agriculture and biology fields because of their special effects and unique features. One of the most important properties of silver compounds is its disinfecting. The Echium amoenum plants were grown with diurnal regime of 16 h light and 8 h dark at 22–29°C and 150 μmol/(m² s) light gravity. Plants were treated for 20 days in 7 groups including I—control, II—silver nitrate (25 ppm), III—silver nanoparticles (25 ppm), IV—silver nanoparticles plus silver nitrate (25 ppm), V—silver nitrate (50 ppm), VI—silver nanoparticles (50 ppm) and VII—silver nanoparticles plus silver nitrate (50 ppm). Results showed that anthocyanins content in groups II, III, V, VI and VII were significantly increased. Total flavonoid content was significantly increased under all treatments compared with untreated plants. Increased total phenol content was observed upon plant exposure to II, IV, V, VI and VII. Regarding the lipid peroxidation, the plants in II and VII groups showed a remarkable increase of malondialdehyde. Also result showed that DPPH free radical scavenging activity was significantly increased in IV, V, VI and VII groups. These findings correlate with the nanoparticles (NPs) causing increased production of reactive oxygen species.

Monoterpenes, the major components of the essential oils of the mint family, are synthesized in glandular trichomes. In peppermint (Mentha piperita L.) precursors for the biosynthesis of monoterpenes are provided by plastidial methyl-erythritol-phosphate (MEP) pathways. Knowledge regarding regulatory elements modulating isoprenoid biosynthetic pathway and trichome differentiation is rudimentary in mint plant. In this study, we aimed to find dynamic transcriptional responses of MEP pathway and regulatory genes to methyl jasmonate (MeJA) and gibberellic acid (GA₃) in M. piperita by quantitative real time-PCR (qRT-PCR). Moreover, the effects of altered precursor availability on oil composition and yield were evaluated after treatments. Consistent with the up-regulation of most of the MEP pathway genes, induced expression of AP2, WRKY and MYB genes resulted in an increase in oil yield and menthol content, suggesting combinatorial action of the JA-modulated transcription factors (TFs) in elicitation of MEP pathway gene expression. In addition to enhancing expression of some of the MEP pathway genes, GA probably affected trichome formation by induction of a C2H2-type zinc finger protein as a key trichome initiation regulator resulting in a rise in oil and menthol yield. Reduced expression of the C2H2 related TF coincided with the induction of MEP pathway genes, suggesting that the C2H2 TF may act as potential transcriptional repressor in the MEP pathway. Moreover, WRKY may regulate C2H2 and AP2 genes expression to control JA-elicited synthesis of terpenoids in M. piperita. These results provide insights related to the underlying mechanism of transcriptional regulation of terpenoids and trichome formation.