Chlorophyll fluorescence as a tool for nutrient status identification in rapeseed plants

In natural conditions, plants growth and development depends on environmental conditions, including the availability of micro- and macroelements in the soil. Nutrient status should thus be examined not by establishing the effects of single nutrient deficiencies on the physiological state of the plant but by combinations of them. Differences in the nutrient content significantly affect the photochemical process of photosynthesis therefore playing a crucial role in plants growth and development. In this work, an attempt was made to find a connection between element content in (i) different soils, (ii) plant leaves, grown on these soils and (iii) changes in selected chlorophyll a fluorescence parameters, in order to find a method for early detection of plant stress resulting from the combination of nutrient status in natural conditions. To achieve this goal, a mathematical procedure was used which combines principal component analysis (a tool for the reduction of data complexity), hierarchical k-means (a classification method) and a machine-learning method—super-organising maps. Differences in the mineral content of soil and plant leaves resulted in functional changes in the photosynthetic machinery that can be measured by chlorophyll a fluorescent signals. Five groups of patterns in the chlorophyll fluorescent parameters were established: the ‘no deficiency’, Fe-specific deficiency, slight, moderate and strong deficiency. Unfavourable development in groups with nutrient deficiency of any kind was reflected by a strong increase in F _o and ΔV/Δt ₀ and decline in φ _Po, φ _Eo δ _Ro and φ _Ro. The strong deficiency group showed the suboptimal development of the photosynthetic machinery, which affects both PSII and PSI. The nutrient-deficient groups also differed in antenna complex organisation. Thus, our work suggests that the chlorophyll fluorescent method combined with machine-learning methods can be highly informative and in some cases, it can replace much more expensive and time-consuming procedures such as chemometric analyses.     

Antimicrobial peptides as effective tools for enhanced disease resistance in plants

Plant Cell, Tissue and Organ Culture (PCTOC) - Four serotypes of the dengue virus that can cause severe disease in humans greatly increases the complexity of vaccine development. In this study, we...     

Chlorophyll fluorescence as a tool for evaluation of drought stress in strawberry

The effect of water deficit on chlorophyll fluorescence, sugar content, and growth parameters of strawberry (Fragaria×ananassa Duch. cv. Elsanta) was studied. Drought stress caused significant reductions in leaf water potential, fresh and dry masses, leaf area, and leaf number. A gradual reduction of photochemical quenching (q_P) and quantum efficiency (Φ_PS2) was observed under drought stress while non-photochemical quenching (q_N) increased. Maximum efficiency of photosystem 2 (F_v/F_m) was not affected by drought stress.     

Managing heavy metal toxicity stress in plants: Biological and biotechnological tools

The maintenance of ion homeostasis in plant cells is a fundamental physiological requirement for sustainable plant growth, development and production. Plants exposed to high concentrations of heavy metals must respond in order to avoid the deleterious effects of heavy metal toxicity at the structural, physiological and molecular levels. Plant strategies for coping with heavy metal toxicity are genotype-specific and, at least to some extent, modulated by environmental conditions. There is considerable interest in the mechanisms underpinning plant metal tolerance, a complex process that enables plants to survive metal ion stress and adapt to maintain growth and development without exhibiting symptoms of toxicity. This review briefly summarizes some recent cell biological, molecular and proteomic findings concerning the responses of plant roots to heavy metal ions in the rhizosphere, metal ion-induced reactions at the cell wall-plasma membrane interface, and various aspects of heavy metal ion uptake and transport in plants via membrane transporters. The molecular and genetic approaches that are discussed are analyzed in the context of their potential practical applications in biotechnological approaches for engineering increased heavy metal tolerance in crops and other useful plants.     

Thermoluminescence and P700 redox kinetics as complementary tools to investigate the cyclic/chlororespiratory electron pathways in stress conditions in barley leaves

Cyclic electron flow around photosystem I drives additional proton pumping into the thylakoid lumen, which enhances the protective non-photochemical quenching and increases ATP synthesis. It involves several pathways activated independently. In whole barley leaves, P700 oxidation under far-red illumination and subsequent P700(+) dark reduction kinetics provide a major probe of the activation of cyclic pathways. Two 'intermediate' and 'slow' exponential reduction phases are always observed and they become faster after high light illumination, but dark inactivation of the Benson-Calvin cycle causes the emergence of both a transient in the P700 oxidation and a 'fast' phase in the P700(+) reduction. We investigate here the afterglow (AG) thermoluminescence emission as another tool to detect the activation of cyclic electron pathways from stroma reductants to the acceptor side of photosystem II. This transfer is activated by warming, yielding an AG band at about 45°C. However, treatments that accelerate the 'intermediate' and 'slow' P700(+) reduction phases (brief anoxia, hexose infiltration, fast dehydration of excised leaves) also produced a downshift of this AG band. This pathway ascribable to NADPH dehydrogenase (NDH) would be triggered by a deficit in ATP, while the 'fast' reduction phase corresponding to the ferredoxin plastoquinone reductase pathway is triggered by an overreduction of the photosystem I acceptor pool and is undetected in thermoluminescence. Contrastingly, slow dehydration of unwatered plants did not cause faster reduction of P700(+) nor temperature downshift of the AG band, that is no induction of the NDH pathway, whereas an increased intensity of the AG band indicated a strong NADPH + ATP assimilatory potential.     

The use of solid-state NMR and X-ray crystallography as complementary tools for studying molecular recognition

Solid-state NMR is rapidly becoming available as a routine technique for studying the structure of crystalline or noncrystalline solids. This technique has an advantage over crystallography in that single crystals are not necessary, but it has the disadvantage that the information obtained does not produce a direct picture of the molecule and its environment. On the other hand, solid-state NMR can be done on mixtures, and it gives information about phase distribution in a manner similar to that of X-ray powder pattern analysis.Crystallographic effects such as polymorphism, multiple molecules per asymmetric unit, disorder and salvation can frequently be detected using NMR. Sometimes molecular point group symmetry can also be deduced based on the number of independent nuclei that are detected. The NMR method is sensitive to changes in the electronic structure of a molecule as sensed by the nuclei, and the effects are measured as changes in the isotropic chemical shift of individual nuclei.In this paper, we will give examples of the combined use of X-ray crystallography and ¹³CP/MAS (cross polarization/magic angle spinning) NMR for studying hostguest materials and cocrystals. We have learned how to use NMR to tell us about keto/enol composition in the solid state, to detect the presence of trapped solvent molecules, to detect hydrogen-bond formation and to evaluate molecular conformation and unusual packing pattern effects. We will also present a brief background of the ¹³CP/MAS NMR technique and three case studies in which solid-state NMR and X-ray crystallography are used together to understand materials' structures and properties     

Homeostasis in cucumber plants during low temperature stress

Shoots, roots and whole plants of Cucumis sativus L. cv. Inspektowy Warszawski were subjected to different temperatures. The magnitude and direction of alterations of growth depended on the organ that was submitted to stress conditions. Changes in soluble protein level in leaves and in roots were inversely correlated with changes of total organic nitrogen level in both organs. In spite of differentiated temperature conditions between plant organs, the allometric coefficients and the ratio between maintenance respiration in shoot and in roots remained constant. Such constancy may be treated as an indicator of homeostasis of the whole-plant system. The results point to the importance of both shoot and roots in the response of the plant to temperature stress.     

Metabolic source isotopic pair labeling and genome-wide association are complementary tools for the identification of metabolite–gene associations in plants

The optimal extraction of information from untargeted metabolomics analyses is a continuing challenge. Here, we describe an approach that combines stable isotope labeling, liquid chromatography– mass spectrometry (LC–MS), and a computational pipeline to automatically identify metabolites produced from a selected metabolic precursor. We identified the subset of the soluble metabolome generated from phenylalanine (Phe) in Arabidopsis thaliana, which we refer to as the Phe-derived metabolome (FDM) In addition to identifying Phe-derived metabolites present in a single wild-type reference accession, the FDM was established in nine enzymatic and regulatory mutants in the phenylpropanoid pathway. To identify genes associated with variation in Phe-derived metabolites in Arabidopsis, MS features collected by untargeted metabolite profiling of an Arabidopsis diversity panel were retrospectively annotated to the FDM and natural genetic variants responsible for differences in accumulation of FDM features were identified by genome-wide association. Large differences in Phe-derived metabolite accumulation and presence/absence variation of abundant metabolites were observed in the nine mutants as well as between accessions from the diversity panel. Many Phe-derived metabolites that accumulated in mutants also accumulated in non-Col-0 accessions and was associated to genes with known or suspected functions in the phenylpropanoid pathway as well as genes with no known functions. Overall, we show that cataloguing a biochemical pathway’s products through isotopic labeling across genetic variants can substantially contribute to the identification of metabolites and genes associated with their biosynthesis.

An isotopic labeling and LC–MS pipeline to identify metabolites produced from Phe and its integration with genome-wide association identifies genes associated with the phenylpropanoid pathway.     

Jasmonate-related mutants of Arabidopsis as tools for studying stress signaling

Jasmonates are naturally occurring signal compounds that regulate plant growth and development, and are involved in plant responses to several environmental stress factors. The mode of action of jasmonates has been investigated traditionally by analysis of the effects of exogenous application of these compounds, including identification of jasmonate-responsive genes and determination of their expression and responsive promoter elements. In addition, jasmonate biosynthesis has been studied by identification of biosynthetic enzymes, use of inhibitors and determination of endogenous jasmonate levels. Recently, several mutants defective in jasmonate biosynthesis and signaling have been isolated and their phenotypes shed new light on the role of jasmonates and jasmonate signaling in plant responses to pathogens, insects and ozone.