Regulation Of Plant Metabolism Research Articles

Micronutrient deficiency-induced oxidative stress in plants.

Micronutrients like iron (Fe), zinc (Zn), copper (Cu), manganese (Mn), boron (B), nickel (Ni), and molybdenum (Mo) perform significant roles in the regulation of plant metabolism, growth, and development. Micronutrients, namely Fe, Zn, Cu, Mn, and Ni, are involved in oxidative stress and antioxidant defense as they are cofactors or activators of various antioxidant enzymes, viz., superoxide dismutase (Fe, Cu/Zn, Mn, and Ni), catalase (Fe), and ascorbate peroxidase (Fe). An effort has been made to incorporate recent advances along with classical work done on the micronutrient deficiency-induced oxidative stress and associated antioxidant responses of plants. Deficiency of a micronutrient produces ROS in the cellular compartments. Enzymatic and non-enzymatic antioxidant defense systems are often modulated by micronutrient deficiency to regulate redox balance and scavenge deleterious ROS for the safety of cellular constituents. ROS can strike cellular constituents such as lipids, proteins, and nucleic acids and can destruct cellular membranes and proteins. ROS might act as a signaling molecule and activate the antioxidant proteins by interacting with signaling partners such as respiratory burst oxidase homolog (RBOH), G-proteins, Ca2+, mitogen activated protein kinases (MAPKs), and various transcription factors (TFs). Opinions on probable ROS signaling under micronutrient deficiency have been described in this review. However, further research is required to decipher micronutrient deficiency-induced ROS generation, perception, and associated downstream signaling events, leading to the development of antioxidant responses in plants.

Nitrogen-fixing bacteria promote growth and bioactive components accumulation of Astragalus mongholicus by regulating plant metabolism and rhizosphere microbiota

BackgroundThe excessive application of chemical fertilizers in the cultivation of Astragalus mongholicus Bunge results in a reduction in the quality of the medicinal plant and compromises the sustainable productivity of the soil. PGPB inoculant is a hot topic in ecological agriculture research. In the cultivation of Astragalus mongholicus, the screened nitrogen-fixing bacteria can promote plant growth, however, whether it can promote the accumulation of main bioactive components remains unknown. In this study, mixed inoculants containing 5 strains of growth promoting bacteria (Rhizobium T16, Sinorhizobium T21, Bacillus J1, Bacillus G4 and Arthrobacter J2) were used in the field experiment. The metabolic substances in the root tissues of Astragalus mongholicus were identified during the harvest period by non-targeted metabolomics method, and the differential metabolites between groups were identified by statistical analysis. Meanwhile, high-throughput sequencing was performed to analyze the changes of rhizosphere soil and endophytic microbial community structure after mixed microbial treatment.ResultsThe results of non-targeted metabolism indicated a significant increase in the levels of 26 metabolites after treatment including 13 flavonoids, 3 saponins and 10 other components. The contents of three plant hormones (abscisic acid, salicylic acid and spermidine) also increased after treatment, which presumed to play an important role in regulating plant growth and metabolism. Studies on endosphere and rhizosphere bacterial communities showed that Rhzobiaceae, Micromonosporaceae, and Hypomicrobiaceae in endophytic, and Oxalobactereae in rhizosphere were significantly increased after treatment. These findings suggest their potential importance in plant growth promotion and secondary metabolism regulation.ConclusionsThis finding provides a basis for developing nitrogen-fixing bacteria fertilizer and improving the ecological planting efficiency of Astragalus mongholicus.

Relevance and regulation of alternative splicing in plant secondary metabolism: current understanding and future directions.

The secondary metabolism of plants is an essential life process enabling organisms to navigate various stages of plant development and cope with ever-changing environmental stresses. Secondary metabolites, abundantly found in nature, possess significant medicinal value. Among the regulatory mechanisms governing these metabolic processes, alternative splicing stands out as a widely observed post-transcriptional mechanism present in multicellular organisms. It facilitates the generation of multiple mRNA transcripts from a single gene by selecting different splicing sites. Selective splicing events in plants are widely induced by various signals, including external environmental stress and hormone signals. These events ultimately regulate the secondary metabolic processes and the accumulation of essential secondary metabolites in plants by influencing the synthesis of primary metabolites, hormone metabolism, biomass accumulation, and capillary density. Simultaneously, alternative splicing plays a crucial role in enhancing protein diversity and the abundance of the transcriptome. This paper provides a summary of the factors inducing alternative splicing events in plants and systematically describes the progress in regulating alternative splicing with respect to different secondary metabolites, including terpenoid, phenolic compounds, and nitrogen-containing compounds. Such elucidation offers critical foundational insights for understanding the role of alternative splicing in regulating plant metabolism and presents novel avenues and perspectives for bioengineering.

LED streetlamps alter tree architecture, downregulate the photosynthetic process and alter the sugar metabolism of Populus alba L.

The escalating issue of light pollution in urban environments poses multifaceted challenges, affecting not only the nocturnal sky but also exerting intricate influences on plant physiology. This study delves into the physiological responses of an urban ornamental tree, Populus alba L. clone DI-1, to varying intensities of streetlamp LED night lighting (NL), a shift from traditional High-Pressure Sodium lamps. The investigation “sheds light” on the molecular pathways underlying observed physiological regulations, aiming to offer a comprehensive understanding of the manifold effects of NL on this tree species. NL altered tree architecture, i.e. increased branch length and diameters, underscoring the dynamic response of trees to nocturnal artificial lighting conditions. Regarding tree physiology, the NL-triggered net CO2 assimilation (Pn) during the night resulted in limitations in stomatal conductance during daylight hours. This led to a reduction in Pn, particularly during dawn, hindering the quantum yield for the reduction of end acceptors of PSI. Changes in chlorophyll a-to-b proportion and overall concentration, electron transport chain, and gene expression further highlight the intricate interplay between NL and plant metabolic regulation. Notably, the increased gene expression of sugar transporters in both NL trees suggested a responsive shift in sugar and starch metabolism. This was reflected in the absence of a starch accumulation during daylight hours in NL leaves. The study emphasizes the need for a holistic approach to urban lighting, considering its profound impact on photosynthesizing citizens. These findings highlight the pressing need for the development of innovative lighting spectra with reduced impact on plant physio-chemistry while ensuring visibility for citizen safety.

NMR and LC–MS-based metabolomics to investigate the efficacy of a commercial bio stimulant for the treatment of wheat (Triticum aestivum)

IntroductionBio stimulants are substances and/or microorganisms that are used to improve plant growth and crop yields by modulating physiological processes and metabolism of plants. While research has primarily focused on the broad effects of bio stimulants in crops, understanding their cellular and molecular influences in plants, using metabolomic analysis, could elucidate their effectiveness and offer possibilities for fine-tuning their application. One such bio stimulant containing galacturonic acid as elicitor is used in agriculture to improve wheat vigor and strengthen resistance to lodging.ObjectiveHowever, whether a metabolic response is evolved by plants treated with this bio stimulant and the manner in which the latter might regulate plant metabolism have not been studied.MethodTherefore, the present study used 1H-NMR and LC–MS to assess changes in primary and secondary metabolites in the roots, stems, and leaves of wheat (Triticum aestivum) treated with the bio stimulant. Orthogonal partial least squares discriminant analysis effectively distinguished between treated and control samples, confirming a metabolic response to treatment in the roots, stems, and leaves of wheat.ResultsFold-change analysis indicated that treatment with the bio stimulation solution appeared to increase the levels of hydroxycinnamic acid amides, lignin, and flavonoid metabolism in different plant parts, potentially promoting root growth, implantation, and developmental cell wall maturation and lignification.ConclusionThese results demonstrate how non-targeted metabolomic approaches can be utilized to investigate and monitor the effects of new agroecological solutions based on systemic responses.

Genome-wide characterization of the bHLH gene family in Gynostemma pentaphyllum reveals its potential role in the regulation of gypenoside biosynthesis

BackgroundGynostemma pentaphyllum, an ancient Chinese herbal medicine, serves as a natural source of gypenosides with significant medicinal properties. Basic helix-loop-helix (bHLH) transcription factors play pivotal roles in numerous biological processes, especially in the regulation of secondary metabolism in plants. However, the characteristics and functions of the bHLH genes in G. pentaphyllum remain unexplored, and their regulatory role in gypenoside biosynthesis remains poorly elucidated.ResultsThis study identified a total of 111 bHLH members in G. pentaphyllum (GpbHLHs), categorizing them into 26 subgroups based on shared conserved motif compositions and gene structures. Collinearity analysis illustrated that segmental duplications predominately lead to the evolution of GpbHLHs, with most duplicated GpbHLH gene pairs undergoing purifying selection. Among the nine gypenoside-related GpbHLH genes, two GpbHLHs (GpbHLH15 and GpbHLH58) were selected for further investigation based on co-expression analysis and functional prediction. The expression of these two selected GpbHLHs was dramatically induced by methyl jasmonate, and their nuclear localization was confirmed. Furthermore, yeast one-hybrid and dual-luciferase assays demonstrated that GpbHLH15 and GpbHLH58 could bind to the promoters of the gypenoside biosynthesis pathway genes, such as GpFPS1, GpSS1, and GpOSC1, and activate their promoter activity to varying degrees.ConclusionsIn conclusion, our findings provide a detailed analysis of the bHLH family and valuable insights into the potential use of GpbHLHs to enhance the accumulation of gypenosides in G. pentaphyllum.

A perspective on varied fungal virulence factors causing infection in host plants.

Pathogenic fungi and their spores are ubiquitously present and invade the tissues of higher living plants causing pathogenesis and inevitably death or retarded growth. A group of fungi kills its hosts and consume the dead tissues (necrotrophs), while others feed on living tissue (biotrophs) or combination of two (hemibiotrophs). A number of virulent factors is used by fungal pathogens to inhabit new hosts and cause illness. Fungal pathogens develop specialized structures for complete invasion into plant organs to regulate pathogenic growth. Virulence factors like effectors, mycotoxins, cell wall degrading enzymes and organic acids have varied roles depending on the infection strategy and assist the pathogens to possess control on living tissues of the plants. Infection strategies employed by fungi generally masks the plant defense mechanism, however necrotrophs are best known to harm plant tissues with their poisonous secretion. Interestingly, the effector chemicals released by Biotrophs reduce plant cell growth and regulate plant metabolism in their advantage causing no direct death. All these virulence tools cause huge loss to the agricultural product of pre- harvest crops and post-harvest yields causing low output leading to huge economic losses. This review focusses on comprehensive study of range of virulence factors of the pathogenic fungi responsible for their invasion inside the healthy tissues of plants. The compiled information would influence researchers to design antidote against all virulence factors of fungi relevant to their area of research which could pave way for protection against plant pathogenesis.

Study on the auxin-like activity of organic compounds extracted from corn waste hydrochar prepared by hydrothermal carbonization

ABSTRACT This work studied the auxin-like activity of liquid and solid hydrochar from aboveground corn biomass prepared using hydrothermal carbonization (HTC). Understanding the action of organic compounds in regulating plant metabolism is important to develop strategies to improve plant growth and production. Bioassays were performed by testing liquid hydrochar concentrations in the range of 0.0557-5570.0 mg carbon L−1; and solid hydrochar (via extracted dissolved organic matter, DOM) in the range of 0.026-2600.0 mg carbon L−1, using seeds of Lactuca sativa. SEM, ATR-FTIR, and Py-GC/MS were applied to assess the effect of HTC on hydrochar production/composition. Liquid hydrochar presented an intense bioactivity, completely inhibiting the germination of testing seeds at higher concentrations. Liquid hydrochar also was considerably more bioactive. Py-GC/MS allowed the identification of the molecules involved in IAA-like effects: carboxylic acids (linear and aromatic) and amino acids. The concentration of more bioactive molecules, rather than their simple presence in the hydrochar fraction, determined the bio-stimulating effect, besides an excellent linear regression between the auxin-like effect and the concentration of active molecules.

The Plant Growth Regulators: Advances, their applications and Potential Uses in Agriculture – A Review

Plant growth regulators (PGRs) or plant hormones are the chemical species that profoundly influence the growth and differentiation of various parts of plant. PGRs called biostimulats or bioinhibitors, act inside plant cells to stimulate or inhibit specific enzymes or enzymes systems and help regulate plant metabolism. To study on this review is the brief introduction and applications of various plant growth regulators including auxins, gibberellins, cytokinins, ethylene, abscisic acid, brassinosteroids and jasmonates, triacontanol, triazoles and polyamines. Several novel plant growth regulators discovered in the recent past includes compounds like Melatonin, Serotonin, Strigolactone, Harzianolide and Karrikins. This review presents a Recent Advances in Use of Plant Growth Regulators (PGRs), the Plant growth regulators (PGRs) and their applications and Novel Plant Growth Regulators and their Potential Uses in Agriculture.

Применение цианобактерий в качестве удобрений для сельскохозяйственных культур растений

Every day, as the world population grows, the need for nutrients also increases, and the scale and intensity of agriculture increases. At the same time, there is a need for renewable, more environmentally friendly fertilizers compared to synthetic ones. One of these fertilizers is phytostimulants based on cyanobacteria. Cyanobacteria are photosynthetic prokaryotes widespread in nature. They are resistant to environmental factors and some cyanobacteria are able to exist in extreme conditions (for example, the genus Nostoc, which demonstrates resistance to soil salinity). During their life processes, cyanobacteria provide plants with useful exometabolites. Through phytohormones, these microalgae participate in the signaling pathway of gene expression that regulates plant metabolism. They improve the rhizosphere community of microorganisms, which leads to a strengthened root system and mineral nutrition. Due to these mineral nutrients, cyanobacteria extracts can be used to improve seed germination, plant growth, flowering and fruiting, and to increase the shelf life of fruits after harvest. Exometabolites of cyanobacteria can stimulate various plant reactions, such as stomatal respiration, photosynthesis, nucleic acid synthesis, chlorophyll formation, ion uptake, also inhibit the development of molds. This article presents an analysis of literature data and scientific articles by domestic and foreign researchers, which gives an idea of the potential of cyanobacteria as biofertilizers both in optimal conditions for growth and development of crop plants, and in saline and dry soils. A brief description of the experiments carried out is given and an assessment of their effectiveness is put forward, based on the conclusion of the researchers.

Physiological, Transcriptomic and Metabolomic Response of Basil (O. basilicum Linn. var. pilosum (Willd.) Benth.) to Red and Blue Light

Basil (Ocimum basilicum Linn. var. pilosum (Willd.) Benth.) is an aromatic plant with high nutritional and economic value, and the synthesis and regulation of its active ingredients have been studied in prior research. However, the mechanisms by which red and blue light—the most effective absorption spectra for photosynthesis—regulate the growth and metabolism of basil remain elusive. This study investigated the changes in phenotype, transcriptome, and metabolome in basil under red and blue light. The photosynthetic efficiency and biomass of basil under blue light (B) treatment were higher than those under white light (W), while red light (R) decreased photosynthesis and biomass. Metabolomic analysis showed that 491 significantly differentially accumulated metabolites were identified between the W and B groups, while 630 differentially accumulated metabolites were identified between the W and R groups. The DAMs were mainly enriched in pathways such as biosynthesis of secondary metabolites, monoterpenoid biosynthesis, limonene and pinene degradation, etc. In addition, transcriptomic analysis revealed that 34,760 and 29,802 differentially expressed genes were detected in the W vs. B pair and the W vs. R pair, respectively, while differentially expressed genes were divided into different unique subclasses, suggesting that they respond to light quality in specific ways. Overall, this work will not only enrich knowledge of the molecular mechanisms of light spectra’s regulation of plant metabolism, but also provide a theoretical basis and guidance for the molecular improvement and quality cultivation of basil.

Key role of phenol enzymes metabolism in the legume-rhizobial symbiosis under different water supply regimes

The legume-rhizobium interaction induces formation of specific reactions that take metabolism in the host plant up to a new functional level, increasing its tolerance to unfavourable cultivation conditions. Our objective was to study the participation of key enzymes – phenylalanine ammonia lyase, guaiacol peroxidase, and polyphenol oxidases – in the phenol-metabolism processes and synthesis of a broad spectrum of secondary metabolites in soybean plants that have established symbiotic interactions with rhizobia of varying effectiveness during optimal and insufficient water supplies. In our studies, we used symbiotic systems of soybean and rhizobia (Bradyrhizobium japonicum) that varied in efficiency and virulence. In the period of active nitrogen fixation by soybean, from the third-true-leaf stage until budding, we created different water-supply regimes for the plants, including optimal watering at the level of 60% of full field capacity (control) and insufficient, at the level of 30% (drought). When the soybean was flowering, we recovered the optimal level of water supply (resumed watering). In the studies, we employed microbiological, biochemical, and physiological approaches. We determined the specificity of how key enzymes of the phenol metabolism such as phenylalanine ammonia lyase, polyphenol oxidase and guaiacol peroxidase in the nodules, roots, and leaves of the soybean reacted to different levels of water supply, depending on the functional efficiency of the symbiotic system involving strains of B. japonicum, varying in effectiveness and virulence. In the effective soybean-rhizobium symbiosis, there occurred insignificant changes in the activity of phenol-metabolism enzymes in the nodules, roots, and leaves during drought and after action of the stress. This evidence is that in symbiosis with effective rhizobia B1-20, soybean could realize its own defensive systems that regulate optimal functioning of phenol metabolism in dehydration conditions. In the low-effective 107 and ineffective 604k symbiotic systems of soybean, there was observed unstable dynamics of the activity of enzymes in leaves and roots, manifested in intensification or inhibition of their activity levels during drought or post-stress period. This indicates malfunctioning of the processes associated with phenol metabolism in the soybean plants. We concluded that tolerance of legume-rhizobium symbiosis to water deprivation depends on mutual involvements of the both symbiotic partners – host plant and rhizobia, their ability to fully realize the defensive systems for activation of the key enzymatic complexes taking part in regulation of phenol metabolism in plants.

The transcription factor NtERF13a enhances abiotic stress tolerance and phenylpropanoid compounds biosynthesis in tobacco

The AP2/ERF (APETALA2/ETHYLENE RESPONSE FACTOR) transcription factors play multiple roles in modulating the biosynthesis of diverse specialized metabolites in response to various environmental stresses. ERF13 has been shown to participate in plant resistance to biotic stress as well as in repressing the synthesis of fatty acid. However, its full roles in regulating plant metabolism and stress resistance still remains to be further studied. In this study, we identified two NtERF genes from N. tabacum genome that belong to Ⅸa subgroup of ERF family. Over-expression and knock-out of NtERF13a showed that NtERF13a could enhance plant resistance to salt and drought stresses, as well as promoted the biosynthesis of chlorogenic acid (CGA), flavonoids, and lignin in tobacco. Transcriptome analysis between WT and NtERF13a-OE plants revealed 6 differentially expressed genes (DEGs) that encode enzymes catalyzing the key steps of phenylpropanoid pathway. Chromatin immunoprecipitation, Y1H, and Dual-Luc assays further clarified that NtERF13a could directly bind to the fragments containing GCC box or DRE element in the promoters of NtHCT, NtF3'H, and NtANS genes to induce the transcription of these genes. Knock-out of NtHCT, NtF3'H, or NtANS in the NtERF13a-OE background significantly repressed the increase of phenylpropanoid compound contents caused by over-expression of NtERF13a, indicating that the promotion of NtERF13a on the phenylpropanoid compound contents depends on the activity of NtHCT, NtF3'H, and NtANS. Our study demonstrated new roles of NtERF13a in promoting plant resistance to abiotic stresses, and provided a promising target for modulating the biosynthesis of phenylpropanoid compounds in tobacco.

Effective Administration of Plant Growth Regulators in Horticultural Crops: A Review

Natural and synthetic plant growth regulators have been used with increasing frequency to modify crop plants by changing the rate or pattern, or both, of their responses to the internal and external factors that govern development from germination. The use of plant growth regulators (PGRs) in modern horticulture is well established, particularly in horticulture in industrially advanced countries, and their application is fast picking up in developing nations as well. The research review indicated that the use of plant growth regulators, regulation of plant metabolism, control of flowering, effects on fruit set and development, control of abscission, Breaking of Seed dormancy and seed germination, enhancing and regulation of flowering, controlling flower drop, fruit thinning, fruit setting, parthenocarpy, post-harvest management and extending the shelf life of horticultural crops.

Blue light promotes ascorbate synthesis by deactivating the PAS/LOV photoreceptor that inhibits GDP-L-galactose phosphorylase.

Ascorbate (vitamin C) is an essential antioxidant in fresh fruits and vegetables. To gain insight into the regulation of ascorbate metabolism in plants, we studied mutant tomato plants (Solanum lycopersicum) that produce ascorbate-enriched fruits. The causal mutation, identified by a mapping-by-sequencing strategy, corresponded to a knock-out recessive mutation in a class of photoreceptor named PAS/LOV protein (PLP), which acts as a negative regulator of ascorbate biosynthesis. This trait was confirmed by CRISPR/Cas9 gene editing and further found in all plant organs, including fruit that accumulated 2 to 3 times more ascorbate than in the WT. The functional characterization revealed that PLP interacted with the 2 isoforms of GDP-L-galactose phosphorylase (GGP), known as the controlling step of the L-galactose pathway of ascorbate synthesis. The interaction with GGP occurred in the cytoplasm and the nucleus, but was abolished when PLP was truncated. These results were confirmed by a synthetic approach using an animal cell system, which additionally demonstrated that blue light modulated the PLP-GGP interaction. Assays performed in vitro with heterologously expressed GGP and PLP showed that PLP is a noncompetitive inhibitor of GGP that is inactivated after blue light exposure. This discovery provides a greater understanding of the light-dependent regulation of ascorbate metabolism in plants.

New insights into the regulation of plant metabolism by O-acetylserine: sulfate and beyond.

Under conditions of sulfur deprivation, O-acetylserine (OAS) accumulates, which leads to the induction of a common set of six genes, called OAS cluster genes. These genes are induced not only under sulfur deprivation, but also under other conditions where OAS accumulates, such as shift to darkness and stress conditions leading to reactive oxygen species (ROS) or methyl-jasmonate accumulation. Using the OAS cluster genes as a query in ATTED-II, a co-expression network is derived stably spanning several hundred conditions. This allowed us not only to describe the downstream function of the OAS cluster genes but also to score for functions of the members of the co-regulated co-expression network and hence the effects of the OAS signal on the sulfate assimilation pathway and co-regulated pathways. Further, we summarized existing knowledge on the regulation of the OAS cluster and the co-expressed genes. We revealed that the known sulfate deprivation-related transcription factor EIL3/SLIM1 exhibits a prominent role, as most genes are subject to regulation by this transcription factor. The role of other transcription factors in response to OAS awaits further investigation.

Histone chaperone NUCLEOSOME ASSEMBLY PROTEIN 1 proteins affect plant growth under nitrogen deficient conditions in Arabidopsis thaliana.

Nitrogen (N) availability is one of the most important factors regulating plant metabolism and growth as it affects global gene expression profiles. Dynamic changes in chromatin structure, including histone modifications and nucleosome assembly/disassembly, have been extensively shown to regulate gene expression under various environmental stresses in plants. However, the involvement of chromatin related changes in plant nutrient responses has been demonstrated only in a few studies to date. In this study, we investigated the function of histone chaperone NUCLEOSOME ASSEMBLY PROTEIN1 (NAP1) proteins under N deficient conditions in Arabidopsis. In the nap1;1 nap1;2 nap1;3 triple mutant (m123-1), the expression of N-responsive marker genes and growth of lateral roots were decreased under N deficient conditions. In addition, the m123-1 plants showed a delay in N deficiency-induced leaf senescence. Taken together, these results suggest that NAP1s affect plant growth under N deficient conditions in Arabidopsis.

Jasmonic acid regulates the biosynthesis of medicinal metabolites via the JAZ9-MYB76 complex in Salvia miltiorrhiza.

Jasmonic acid (JA) signaling pathway plays an important role in tanshinone and phenolic acid biosynthesis in Salvia miltiorrhiza. However, the specific regulatory mechanism remains largely unclear. Previous work showed that a JASMONATE ZIM-domain (JAZ) protein, SmJAZ9, acted as a repressor of tanshinone production in S. miltiorrhiza. In this study, we revealed that SmJAZ9 reduced both phenolic acid accumulation and related biosynthetic gene expression, confirming that SmJAZ9 also negatively affected phenolic acid biosynthesis. Then, we identified a novel MYB transcription factor, SmMYB76, which interacted with SmJAZ9. SmMYB76 repressed phenolic acid biosynthesis by directly downregulating SmPAL1, Sm4CL2, and SmRAS1. Further investigation demonstrated that JA mediated phenolic acids biosynthesis via SmJAZ9-SmMYB76 complex. Taken together, these findings state the molecular mechanism that SmJAZ9-SmMYB76 regulated phenolic acid biosynthesis at the transcriptional and protein levels, which provided new insights into JA signaling pathway regulating plant metabolism.

Mechanisms of Growth Promotional and Protective Effects of Endophytic PGP-Bacteria in Wheat Plants Under the Impact of Drought (Review)

The review is devoted to the analysis and systematization of modern data on the participation of endophytic plant growth-promoting (PGP) bacteria in the regulation of growth, development, yield formation, and stress resistance of cultivated plants, mainly spring wheat as the main bread crop. Presently known data on the interaction of plants with PGP-bacteria under normal and drought conditions are described. Particular attention is paid to the molecular mechanisms of regulation of plant metabolism by PGP-bacteria, as well as their role in reducing the negative effects of drought, achieved by modulating various processes in plants, for example, improving the supply of moisture and mineral nutrients, and activating the antioxidant and osmoprotective plant systems. A key role in the adaptation and resistance/tolerance of plants caused by PGP-bacteria are played by their ability to produce various metabolites with the properties of biologically active substances, including substances with antimicrobial and hormonal activity, enzymes and other compounds. Information about the endophytic microbiome of wheat is given, the elucidation of the role and functions of which in plant stress response and adaptation is necessary for the development of effective, safe strategies for their practical application in order to maximize the adaptation and productive potential of wheat under changing environmental conditions.

Differences of nitrogen metabolism in date palm (Phoenix dactylifera) seedlings subjected to water deprivation and salt exposure.

Drought and salt exposure are among the most prevalent and severe abiotic stressors causing serious agricultural yield losses, alone and in combination. Little is known about differences and similarities in the effects of these two stress factors on plant metabolic regulation, particularly on nitrogen metabolism. Here, we studied the effects of water deprivation and salt exposure on water relations and nitrogen metabolites in leaves and roots of date palm seedlings. Both, water deprivation and salt exposure had no significant effects on plant water content or stable carbon (C) and nitrogen (N) isotope signatures. Significant effects of water deprivation on total C and N concentrations were only observed in roots, i.e., decreased total C and increased total N concentrations. Whereas salt exposure initially decreased total C and increased total N concentrations significantly in roots, foliar total C concentration was increased upon prolonged exposure. Initially C/N ratios declined in roots of plants from both treatments and upon prolonged salt exposure also in the leaves. Neither treatment affected soluble protein and structural N concentrations in leaves or roots, but resulted in the accumulation of most amino acids, except for glutamate and tryptophan, which remained stable, and serine, which decreased, in roots. Accumulation of the most abundant amino acids, lysine and proline, was observed in roots under both treatments, but in leaves only upon salt exposure. This finding indicates a similar role of these amino acids as compatible solutes in the roots in response to salt und drought, but not in the leaves. Upon prolonged treatment, amino acid concentrations returned to levels found in unstressed plants in leaves of water deprived, but not salt exposed, plants. The present results show both water deprivation and salt exposure strongly impact N metabolism of date palm seedlings, but in a different manner in leaves and roots.