Plant Cell Metabolism Research Articles

Integration of Mitoflash and Time-Series Transcriptomics Facilitates Energy Dynamics Tracking and Substrate Supply Analysis of Floral Thermogenesis in Lotus.

The high biosynthetic and energetic demands of floral thermogenesis render thermogenic plants the ideal systems to characterize energy metabolism in plants, but real-time tracking of energy metabolism in plant cells remains challenging. In this study, a new method was developed for tracking the mitochondrial energy metabolism at the single mitochondria level by real-time imaging of mitochondrial superoxide production (i.e., mitoflash). Using this method, we observed the increased mitoflash frequencies in the receptacles of Nelumbo nucifera Gaertn. at the thermogenic stages. This increase, combined with the higher expression of antioxidant response-related genes identified through time-series transcriptomics at the same stages, shows us a new regulatory mechanism for plant redox balance. Furthermore, we found that the upregulation of respiratory metabolism-related genes during the thermogenic stages not only correlates with changes in mitoflash frequency but also underscores the critical roles of these pathways in ensuring adequate substrate supply for thermogenesis. Metabolite analysis revealed that sugars are likely one of the substrates for thermogenesis and may be transported over long distances by sugar transporters. Taken together, our findings demonstrate that mitoflash is a reliable tool for tracking energy metabolism in thermogenic plants and contributes to our understanding of the regulatory mechanisms underlying floral thermogenesis.

Determination of the molecular weight of native molecules of γ-hydroxybutyrate dehydrogenase isoforms obtained from maize (Zea mays L.) seedlings by gel chromatography

It is known that under oxygen deficiency the functioning of the tricarboxylic acid cycle is impaired, resulting in the activation of an alternative pathway, the GABA shunt. It maintains the functioning of the citric acid cycle by providing succinic acid. The key phase of this bypass is a reaction catalysed by succinate semialdehyde dehydrogenase (SSADH, EC 1.1.1.16). Under oxygen deficiency, SSADH ceases to function efficiently. This leads to the accumulation of succinic acid semialdehyde in the mitochondrial matrix and its high level adversely affects the plant cell metabolism. γ–hydroxybutyrate dehydrogenase (HBDH, EC 1.1.1.61) is an enzyme belonging to the group of oxidoreductases. It transforms γ–hydroxybutyrate into succinic acid semialdehyde, participating in the process of its detoxification, which is important in the maintenance of plant metabolism under oxygen deficiency. To date, unfortunately, there are no data on the biochemical and kinetic features of γ–hydroxybutyrate dehydrogenase. In this regard, our laboratory developed a method for purification of HBDH from green maize leaves, which makes it possible to study the physicochemical properties of this enzyme. During the study, we obtained γ-hydroxybutyrate dehydrogenase from 7-day-old seedlings of Zea mays L. by a five-stage purification. Homogenised plant material with extracted proteins was subjected to two-stage ammonium sulphate fractionation. The catalytic activity was determined spectrophotometrically at λ=340 nm by the amount of reduced NAD+. To remove ammonium salts, we used gel filtration through Sephadex G-25. Proteins were separated according to their charge by DEAE-Sephacel ion exchange chromatography. The enzyme was desorbed using a linear sodium chloride gradient (100-300 mM). The use of gel chromatography through Sephadex G-200 made it possible to determine the molecular mass of the purified enzyme isoforms. The homogeneity of enzyme preparations was confirmed by electrophoresis in polyacrylamide gel with universal AgNO3 staining. We used the tetrazolium method to confirm that the obtained protein preparations were γ-hydroxybutyrate dehydrogenase. As a result, homogeneous preparations of two isoforms of the enzyme (HBDH1 and HBDH2) were obtained. The first isoform of γ-hydroxybutyrate dehydrogenase was 185.7 times purified with a yield of 10% and had a specific activity of 343.6 U/mg of protein. The purification rate of the second isoform was 209 times with a yield of 7.74%. The specific activity of the obtained preparation was 386.7 U/mg of protein. Using gel chromatography through Sephadex G-200, we determined the molecular mass of native molecules of hydroxybutyrate dehydrogenase. We found that in 7-day-old maize seedlings the investigated enzyme was presented in low-molecular and high-molecular forms: for HBDH1 the Mr value was ⁓60.3 kDa, while for HBDH2 the molecular mass of the enzyme was 286 kDa.

The root-knot nematode effector MiEFF12 targets the host ER quality control system to suppress immune responses and allow parasitism.

Root-knot nematodes (RKNs) are microscopic parasitic worms able to infest the roots of thousands of plant species, causing massive crop yield losses worldwide. They evade the plant's immune system and manipulate plant cell physiology and metabolism to transform a few root cells into giant cells, which serve as feeding sites for the nematode. RKN parasitism is facilitated by the secretion in planta of effector molecules, mostly proteins that hijack host cellular processes. We describe here a conserved RKN-specific effector, effector 12 (EFF12), that is synthesized exclusively in the oesophageal glands of the nematode, and we demonstrate its function in parasitism. In the plant, MiEFF12 localizes to the endoplasmic reticulum (ER). A combination of RNA-sequencing analysis and immunity-suppression bioassays revealed the contribution of MiEFF12 to the modulation of host immunity. Yeast two-hybrid, split luciferase and co-immunoprecipitation approaches identified an essential component of the ER quality control system, the Solanum lycopersicum plant bap-like (PBL), and basic leucine zipper 60 (BZIP60) proteins as host targets of MiEFF12. Finally, silencing the PBL genes in Nicotiana benthamiana decreased susceptibility to Meloidogyne incognita infection. Our results suggest that EFF12 manipulates PBL function to modify plant immune responses to allow parasitism.

Exogenous application of 5-NGS increased osmotic stress resistance by improving leaf photosynthetic physiology and antioxidant capacity in maize.

Drought is a critical limiting factor affecting the growth and development of spring maize (Zea mays L.) seedlings in northeastern China. Sodium 5-nitroguaiacol (5-NGS) has been found to enhance plant cell metabolism and promote seedling growth, which may increase drought tolerance. In the present study, we investigated the response of maize seedlings to foliar application of a 5-NGS solution under osmotic stress induced by polyethylene glycol (PEG-6000). Four treatment groups were established: foliar application of distilled water (CK), foliar application of 5-NGS (NS), osmotic stress + foliar application of distilled water (D), and osmotic stress + foliar application of 5-NGS (DN). Plant characteristics including growth and photosynthetic and antioxidant capacities under the four treatments were evaluated. The results showed that under osmotic stress, the growth of maize seedlings was inhibited, and both the photosynthetic and antioxidant capacities were weakened. Additionally, there were significant increases in the proline and soluble sugar contents and a decrease in seedling relative water content (RWC). However, applying 5-NGS alleviated the impact of osmotic stress on maize seedling growth parameters, particularly the belowground biomass, with a dry mass change of less than 5% and increased relative water content (RWC). Moreover, treatment with 5-NGS mitigated the inhibition of photosynthesis caused by osmotic stress by restoring the net photosynthetic rate (Pn) through an increase in chlorophyll content, photosynthetic electron transport, and intercellular CO2 concentration (Ci). Furthermore, the activity of antioxidant enzymes in the aboveground parts recovered, resulting in an approximately 25% decrease in both malondialdehyde (MDA) and H2O2. Remarkably, the activity of enzymes in the underground parts exhibited more significant changes, with the contents of MDA and H2O2 decreasing by more than 50%. Finally, 5-NGS stimulated the dual roles of soluble sugars as osmoprotectants and energy sources for metabolism under osmotic stress, and the proline content increased by more than 30%. We found that 5-NGS played a role in the accumulation of photosynthates and the effective distribution of resources in maize seedlings. Based on these results, we determined that foliar application of 5-NGS may improve osmotic stress tolerance in maize seedlings. This study serves as a valuable reference for increasing maize yield under drought conditions.

Cysteine oxidation as a regulatory mechanism of Arabidopsis plastidial NAD-dependent malate dehydrogenase.

Malate dehydrogenases (MDHs) catalyze a reversible NAD(P)-dependent-oxidoreductase reaction that plays an important role in central metabolism and redox homeostasis of plant cells. Recent studies suggest a moonlighting function of plastidial NAD-dependent MDH (plNAD-MDH; EC 1.1.1.37) in plastid biogenesis, independent of its enzyme activity. In this study, redox effects on activity and conformation of recombinant plNAD-MDH from Arabidopsis thaliana were investigated. We show that reduced plNAD-MDH is active while it is inhibited upon oxidation. Interestingly, the presence of its cofactors NAD+ and NADH could prevent oxidative inhibition of plNAD-MDH. In addition, a conformational change upon oxidation could be observed via non-reducing SDS-PAGE. Both effects, its inhibition and conformational change, were reversible by re-reduction. Further investigation of single cysteine substitutions and mass spectrometry revealed that oxidation of plNAD-MDH leads to oxidation of all four cysteine residues. However, cysteine oxidation of C129 leads to inhibition of plNAD-MDH activity and oxidation of C147 induces its conformational change. In contrast, oxidation of C190 and C333 does not affect plNAD-MDH activity or structure. Our results demonstrate that plNAD-MDH activity can be reversibly inhibited, but not inactivated, by cysteine oxidation and might be co-regulated by the availability of its cofactors in vivo.

Biopriming of Momordica charantia Seeds with Enterobacter to Improve Nutritional and Biochemical Attributes

The increasing world population needs a standard balanced diet to address malnutrition problems. For this purpose, seed priming is one of the best techniques, which helps to increase the production of functional and nutritional food crops. Different techniques have been used for seed priming, but biological priming is the most frequently used because biocontrol agents offer a friendly environment for the growth of food crops. In this study, Momordica charantia L. seeds were subjected to a strain of Enterobacter sp. FD17 as a biocontrol agent at different time exposures (i.e., 24 h, 48 h, and 72 h). Leaf growth, flavonoids, chlorophyll content, amino acids, soluble sugars, protein, and total soluble phenolics were studied in the vegetative stage. The yield of nutritive components was evaluated from fruit, peel, and pulp of M. charantia. Biopriming was revealed to improve the final emergence rate, mean emergence time, seedling vigor, emergence index, and vigor indices I and II. Among the growth parameters, the root (0.45 ± 0.045 g) and shoot fresh weight (1.23 ± 0.05 g), leaf area (15.52 ± 1.5 cm), shoot length (30.33 ± 0.58 cm), number of flowers (6 ± 1.0), fruit weight (96.33 ± 1.15 g), and germination percentage (56.67 ± 11.55%) were also improved. Among biochemical analyses, biopriming improved chlorophyll a (6.33 ± 0.58 mg/g) and b (8.58 ± 2.5 mg/g), total soluble sugar (33.13 ± 2.24%), and total chlorophyll content (9.0 ± 1.5 mg/g). The nutritional analysis showed that free amino acids (1.43 ± 0.02 mg/g), total soluble sugar (42.53 ± 1.65%), ash (20.53 ± 2.57%), and catalase (347.47 ± 34.76 U/g) were increased in fruit, while crude fiber (3.62 ± 0.1%) and peroxidase (5.61 ± 0.34 U/g) in peel and protein and metabolizable energy in peel and fruit were increased. Among the water, acetone, and methanol extracts, the maximum antibacterial activity was shown by methanol extracts of leaves against Gram-negative and Gram-positive bacterial species (i.e., Pseudomonas aeruginosa and Staphylococcus aureus, respectively) with inhibitory diameters of 3 mm. Biopriming also improved the phenolic contents in the leaves and fruits of M. charantia. Biopriming treatment was also revealed to be directly correlated with antiglycation activity. Therefore, biopriming treatment on seeds could be used to manipulate plant cell metabolism with a substantial improvement in phenolic content, antibacterial activity, and growth of M. charantia.

A complex array of factors regulate the activity of Arabidopsis thaliana δ1 -pyrroline-5-carboxylate synthetase isoenzymes to ensure their specific role in plant cell metabolism.

The first and committed step in proline synthesis from glutamate is catalyzed by δ1 -pyrroline-5-carboxylate synthetase (P5CS). Two P5CS genes have been found in most angiosperms, one constitutively expressed to satisfy proline demand for protein synthesis, the other stress-induced. Despite the number of papers to investigate regulation at the transcriptional level, to date, the properties of the enzymes have been subjected to limited study. The isolation of Arabidopsis thaliana P5CS isoenzymes was achieved through heterologous expression and affinity purification. The two proteins were characterized with respect to kinetic and biochemical properties. AtP5CS2 showed KM values in the micro- to millimolar range, and its activity was inhibited by NADP+ , ADP and proline, and by glutamine and arginine at high levels. Mg2+ ions were required for activity, which was further stimulated by K+ and other cations. AtP5CS1 displayed positive cooperativity with glutamate and was almost insensitive to inhibition by proline. In the presence of physiological, nonsaturating concentrations of glutamate, proline was slightly stimulatory, and glutamine strongly increased the catalytic rate. Data suggest that the activity of AtP5CS isoenzymes is differentially regulated by a complex array of factors including the concentrations of proline, glutamate, glutamine, monovalent cationsand pyridine dinucleotides.

Tailoring Plant Cell Growth with Collagen-Starch Biomatrices with Calcium bioMOFs

Biomatrices designed to stimulate the growth of tomato cells were prepared in this study. These biomatrices were composed of collagen-starch (CA) through a system of semi-interpenetrating polymer networks, allowing the inclusion of calcium metal-organic frameworks (MOFs) to facilitate plant metabolic stimulation. BioCaMOFs were prepared under hydrothermal conditions (100°C, 48 h) using Ca(NO3)2 and the essential amino acids L-phenylalanine, L-histidine, and L-tryptophan. A 1 mg of each bioCaMOF was dispersed in the collagen-starch matrix, generating the biomatrices CA-MOFCaF, CA-MOFCaH, and CA-MOFCaT, respectively. Infrared spectroscopy was employed to identify the chemical bonds present in each component of the biomatrices. The results indicated that the CA-MOFCaT biomatrix exhibited increased water swelling capacity (2900 ± 180 %) and the highest crosslinking index (74 ± 4 %). Tomato cells derived from sterile seeds (50,000 cells per biomatrix), both red and green varieties, migrated within the biomatrices, enhancing their metabolic activity. The biomatrices containing bioactive calcium MOFs actively stimulated the metabolism of plant cells for up to 48 hours upon contact. Determining that the biomatrix CA-MOFCaF promotes greater stimulation in green tomato cells, while CA-MOFCaT does so with red tomato cells. Such biomatrices hold promise as effective 3D cultures that promote the metabolism of plant cells and could lead to innovative formulations of biofertilizers.

Large-Scale Production of Specialized Metabolites In Vitro Cultures.

For centuries plants have been intensively utilized as reliable sources of food, flavoring, and pharmaceutical ingredients. However, plant natural habitats are being rapidly lost due to the climate change and agriculture. Plant biotechnology offers a sustainable approach for the bioproduction of specialized plant metabolites. The unique structural features of plant-derived specialized metabolites, such as their safety profile and multi-target spectrum, have led to the establishment of many plant-derived drugs. However, there are still many challenges to overcome regarding the production of these metabolites from plant in vitro systems and establish a sustainable large-scale biotechnological process. These challenges are due to the peculiarities of plant cell metabolism, the complexity of plant specialized metabolite pathways, and the correct selection of bioreactor systems and bioprocess optimization. In this book chapter, we attempted to focus on the advantages of plant in vitro systems and in particular plant cell suspensions for their cultivation as a source of plant-derived specialized metabolites. A state-of-the-art technological platform for plant cell suspension cultivation from callus induction to lab-scale cultivation, extraction, and purification is presented. Possibilities for bioreactor cultivation of plant cell suspensions in benchtop and large-scale volumes are highlighted, including several examples and patents for industrial production of specialized metabolites.

Uptake and Metabolic Conversion of Exogenous Phosphatidylcholines Depending on Their Acyl Chain Structure in Arabidopsis thaliana.

Fungi and plants are not only capable of synthesizing the entire spectrum of lipids de novo but also possess a well-developed system that allows them to assimilate exogenous lipids. However, the role of structure in the ability of lipids to be absorbed and metabolized has not yet been characterized in detail. In the present work, targeted lipidomics of phosphatidylcholines (PCs) and phosphatidylethanolamines (PEs), in parallel with morphological phenotyping, allowed for the identification of differences in the effects of PC molecular species introduced into the growth medium, in particular, typical bacterial saturated (14:0/14:0, 16:0/16:0), monounsaturated (16:0/18:1), and typical for fungi and plants polyunsaturated (16:0/18:2, 18:2/18:2) species, on Arabidopsis thaliana. For comparison, the influence of an artificially synthesized (1,2-di-(3-(3-hexylcyclopentyl)-propanoate)-sn-glycero-3-phosphatidylcholine, which is close in structure to archaeal lipids, was studied. The phenotype deviations stimulated by exogenous lipids included changes in the length and morphology of both the roots and leaves of seedlings. According to lipidomics data, the main trends in response to exogenous lipid exposure were an increase in the proportion of endogenic 18:1/18:1 PC and 18:1_18:2 PC molecular species and a decrease in the relative content of species with C18:3, such as 18:3/18:3 PC and/or 16:0_18:3 PC, 16:1_18:3 PE. The obtained data indicate that exogenous lipid molecules affect plant morphology not only due to their physical properties, which are manifested during incorporation into the membrane, but also due to the participation of exogenous lipid molecules in the metabolism of plant cells. The results obtained open the way to the use of PCs of different structures as cellular regulators.

Transcriptomic and metabolomic analyses reveal that ABA increases the salt tolerance of rice significantly correlated with jasmonic acid biosynthesis and flavonoid biosynthesis

Abscisic acid (ABA) has been shown to mitigate the deleterious effects of abiotic stresses and to regulate plant growth and development. Salinity is one of the important abiotic stresses affecting plant cell metabolism and physiology, which causes serious damages to crops. In this study, we investigated the protective role of exogenous ABA on leaves in response to salinity stress using rice seedlings (two leaf-one heart) subjected to three treatments: ZCK (control), ZS (50 mM NaCl), and ZSA (5 mg L–1 ABA + 50 mM NaCl). We carried out transcriptomic and metabolomic analyses to identify the molecular mechanisms by which ABA protects plants against salt stress. Results showed that 1159 differentially expressed genes (DEGs) (916 up-regulated, 243 down-regulated) and 63 differentially accumulated metabolites (DAMs) (42 up-regulated, 21 down-regulated) were identified between the ZS and ZSA treatments, respectively. In addition, ABA pretreatment regulated the expression pattern of genes responsible for oxidation redox, starch and sucrose metabolism, and phenylpropanoid biosynthesis. The combined transcriptomic and metabolomic analysis revealed that 16 DEGs and 2 DAMs were involved in Flavonoid biosynthesis and 8 DEGs and 2 DAMs were involved alpha-Linolenic acid metabolism which are responsible for salinity stress tolerance through induced by exogenous ABA. Overall, ABA could enhance rice leaves growth and development mainly by regulating flavonoid biosynthesis and linoleic acid metabolism pathway.

Nitric Oxide (NO) and Hydrogen Sulfide (H2S): New Potential Biotechnological Tools for Postharvest Storage of Horticultural Crops

AbstractStorage and maintenance of horticultural products in optimal conditions for a reasonable period, once they have been harvested is a technological challenge. Diverse methods are generally used, i.e., low temperature but, in many cases, it may provoke undesirable collateral effects such as softening or promoting pathogens infections, thus causing their deterioration. Nitric oxide (·NO) and hydrogen sulfide (H2S) are compounds generated endogenously by plants with signaling properties that mediate fruit development and ripening. Additionally, when these molecules are applied exogenously, they can provide benefits such as maintaining the quality of horticultural products and even prolonging their shelf-life once they are stored. This review provides a broad perspective of ·NO and H2S metabolism in plant cells and, in addition, different plant models are described of how the exogenous application of either NO or H2S to horticultural products preserves nutritional quality during postharvest storage. Graphical Abstract

Growth and metabolism of pea (Pisum sativum) via biostimulants based on greener ZnO nanoparticles

The purpose of this study was to identify the most important physiological and biological effects of green synthesis ZnO nanoparticles at a size of 65 nm, biostimulant (Folcare) and interaction biostimulant ZnO NPs on plant growth and metabolism. As our understanding of biostimulants’ preventive and restorative modes of action has increased, it is critical to maintain the best crop output and quality possible. The reduction of fertilizers must be substituted by strategies that improve the nutrients uptake or their utilization by the plants. New processing methods are required as an efficient green process or an integrated (hybrid) process for different new technologies of interest. The effects of NPs, biostimulant, and combination ZnO NPs biostimulant on plant cell metabolism were examined in cytosol, chloroplast, and mitochondria of cells from the stems, roots, and leaves. The interaction NPs/biostimulant had a beneficial effect on the morphological and physiological indicators of plant health than when nanoparticles and biostimulant are applied separately. Folcare biostimulant coupled with zinc oxide nanoparticles improved pea crops growth. The improved of the quality of pea plants can be explained at least, in part, by increase in antioxidant activities during plant growth phenophase.

Dynamics of Organic Acids during the Droplet-Vitrification Cryopreservation Procedure Can Be a Signature of Oxidative Stress in Pogostemon yatabeanus.

Cryopreservation in liquid nitrogen (LN, -196 °C) is a unique option for the long-term conservation of threatened plant species with non-orthodox or limitedly available seeds. In previous studies, a systematic approach was used to develop a droplet-vitrification (DV) cryopreservation protocol for Postemon yatabeanus shoot tips that includes preculture with 10% sucrose, osmoprotection with C4-35%, cryoprotection with A3-80% vitrification solution, and a three-step regrowth starting with the ammonium-free medium. The tricarboxylic acid (TCA) cycle is a crucial component of plant cell metabolism as it is involved in redox state regulation and energy provision. We hypothesized that organic acids (OAs) associated with the TCA and its side reactions indirectly indicate metabolism intensity and oxidative stress development in shoot tips under the cryopreservation procedure. In this study, the contents of 14 OAs were analyzed using gas chromatography-tandem mass spectrometry (GC-MS/MS) in P. yatabeanus shoot tips in a series of treatments including individual steps of the DV procedure, additional stress imposed by non-optimum protocol conditions (no preculture, no osmoprotection, various vitrification solution composition, using vials instead of aluminum foils, etc.) and regrowth on different media with or without ammonium or growth regulators. The possible relation of OA content with the total cryoprotectant (CPA) concentration and shoot tips regeneration percentage was also explored. Regeneration of cryopreserved shoot tips reduced in descending order as follows: standard protocol condition (91%) > non-optimum vitrification solution (ca. 68%) > non-optimum preculture (60-62%) > regrowth medium (40-64%) > no osmoprotection, cryopreservation in vials (28-30%). Five OAs (glycolic, malic, citric, malonic, and lactic) were the most abundant in the fresh (control) shoot tips. The dynamic pattern of OAs during the DV procedure highly correlated (r = 0.951) with the total CPA concentration employed: it gradually increased through the preculture, osmoprotection, and cryoprotection, peaked at cooling/rewarming (6.38-fold above control level), and returned to the fresh control level after 5 days of regrowth (0.89-fold). The contents of four OAs (2-hydroxybutyric, 3-hydroxypropionic, lactic, and glycolic) showed the most significant (10-209-fold) increase at the cooling/rewarming step. Lactic and glycolic acids were the major OAs at cooling/rewarming, accounting for 81% of the total OAs content. The OAs were categorized into three groups based on their dynamics during the cryopreservation protocol, and these groups were differently affected by protocol step modifications. However, there was no straightforward relationship between the dynamics of OAs and shoot tip regeneration. The results suggest that active modulation of OAs metabolism may help shoot tips to cope with osmotic stress and the chemical cytotoxicity\ of CPAs. Further intensive studies are needed to investigate the effect of cryopreservation on cell primarily metabolism and identify oxidative stress-related biomarkers in plant materials.

Effects of Light Intensity on in Vitro Regeneration Of Stevia Rebaudiana Bertoni, Bacopa Monnieri L. And Solanum Tuberosum L.

Light is the most essential factor controlling plant growth, morphogenesis, metabolism and chlorophyll content of plant cells, tissues and organ culture. The present investigations were carried out to find out effects of different light intensities (210, 500, 1000, 1500, 2000, 2500 and 3000 lx) on the regeneration of three plants, namely Stevia rebaudiana Bertoni., Solanum tuberosum L. and Bacopa monnieri L. Results showed that light intensity has a direct effect on plant growth in vitro. There was less time for shoot initiation and the highest mean number of shoots/explants (9.75 ± 3.862) of S. rebaudiana was observed from the nodal explants when the culture was maintained at 1000 lx light conditions. At maximum light intensity (3000 lx) best result was recorded for S. tuberosum. A distinct intensity of light, 1500 lx showed the best outcome both for the number and length of shoots of B. monnieri (p = 0.00). The present study also demonstrated the relationship between root growth and light condition. Bangladesh J. Bot. 52(1): 53-60, 2023 (March)

A dive into the cell wall with Arabidopsis.

One of the many legacies of the work of Michel Caboche is our understanding of plant cell wall synthesis and metabolism thanks to the use of Arabidopsis mutants. Here I describe how he was instrumental in initiating the genetic study of plant cell walls. I also show, with a few examples for cellulose and pectins, how this approach has led to important new insights in cell wall synthesis and how the metabolism of pectins contributes to plant growth and morphogenesis. I also illustrate the limitations of the use of mutants to explain processes at the scale of cells, organs or whole plants in terms of the physico-chemical properties of cell wall polymers. Finally, I sketch how new approaches can cope with these limitations.

Transcriptional repressor RST1 controls salt tolerance and grain yield in rice by regulating gene expression of asparagine synthetase

Salt stress impairs nutrient metabolism in plant cells, leading to growth and yield penalties. However, the mechanism by which plants alter their nutrient metabolism processes in response to salt stress remains elusive. In this study, we identified and characterized the rice (Oryza sativa) rice salt tolerant 1(rst1) mutant, which displayed improved salt tolerance and grain yield. Map-based cloning revealed that the gene RST1 encoded an auxin response factor (OsARF18). Molecular analyses showed that RST1 directly repressed the expression of the gene encoding asparagine synthetase 1 (OsAS1). Loss of RST1 function increased the expression of OsAS1 and improved nitrogen (N) utilization by promoting asparagine production and avoiding excess ammonium (NH4+) accumulation. RST1 was undergoing directional selection during domestication. The superior haplotype RST1Hap III decreased its transcriptional repression activity and contributed to salt tolerance and grainweight. Together, our findings unravel a synergistic regulator of growth and salt tolerance associated with N metabolism and provide a new strategy for the development of tolerant cultivars.

Do Volatiles Affect Bacteria and Plants in the Same Way? Growth and Biochemical Response of Non-Stressed and Cd-Stressed Arabidopsis thaliana and Rhizobium E20-8.

Plant roots are colonized by rhizobacteria, and these soil microorganisms can not only stimulate plant growth but also increase tolerance to stress through the production of volatile organic compounds. However, little is known about the effect that these plant beneficial volatiles may have on bacteria. In this study, the effects on growth and oxidative status of different concentrations of three volatiles already reported to have a positive influence on plant growth (2-butanone, 3-methyl-1-butanol, and 2,3-butanediol) were determined in A. thaliana and Rhizobium sp. strain E20-8 via airborne exposure in the presence and absence of Cd. It was expected to ascertain if the plant and the bacterium are influenced in the same way by the volatiles, and if exposure to stress (Cd) shifts the effects of volatiles on plants and bacteria. Results showed the antioxidant activity of the volatiles protecting the plant cell metabolism from Cd toxicity and increasing plant tolerance to Cd. Effects on bacteria were less positive. The two alcohols (3-methyl-1-butanol and 2,3-butanediol) increased Cd toxicity, and the ketone (2-butanone) was able to protect Rhizobium from Cd stress, constituting an alternative way to protect soil bacterial communities from stress. The application of 2-butanone thus emerges as an alternative way to increase crop production and crop resilience to stress in a more sustainable way, either directly or through the enhancement of PGPR activity.

Genome-Wide Identification of Potential mRNAs in Drought Response in Wheat (Triticum aestivum L.).

Plant cell metabolism inevitably forms an important drought-responsive mechanism, which halts crop productivity. Globally, more than 30% of the total harvested area was affected by dehydration. RNA-seq technology has enabled biologists to identify stress-responsive genes in relatively quick times. However, one shortcoming of this technology is the inconsistent data generation compared to other parts of the world. So, we have tried, here, to generate a consensus by analyzing meta-transcriptomic data available in the public microarray database GEO NCBI. In this way, the aim was set, here, to identify stress genes commonly identified as differentially expressed (p < 0.05) then followed by downstream analyses. The search term “Drought in wheat” resulted in 233 microarray experiments from the GEO NCBI database. After discarding empty datasets containing no expression data, the large-scale meta-transcriptome analytics and one sample proportional test were carried out (Bonferroni adjusted p < 0.05) to reveal a set of 11 drought-responsive genes on a global scale. The annotation of these genes revealed that the transcription factor activity of RNA polymerase II and sequence-specific DNA-binding mechanism had a significant role during the drought response in wheat. Similarly, the primary root differentiation zone annotations, controlled by TraesCS5A02G456300 and TraesCS7B02G243600 genes, were found as top-enriched terms (p < 0.05 and Q < 0.05). The resultant standard drought genes, glycosyltransferase; Arabidopsis thaliana KNOTTED-like; bHLH family protein; Probable helicase MAGATAMA 3; SBP family protein; Cytochrome c oxidase subunit 2; Trihelix family protein; Mic1 domain-containing protein; ERF family protein; HD-ZIP I protein; and ERF family protein, are important in terms of their worldwide proved link with stress. From a future perspective, this study could be important in a breeding program contributing to increased crop yield. Moreover, the wheat varieties could be identified as drought-resistant/sensitive based on the nature of gene expression levels.

Arbuscular Mycorrhizal Fungi Mediated Alleviation of Drought Stress via Non-Enzymatic Antioxidants: A Meta-Analysis.

Drought stress constrains plant cell metabolism and induces the production of reactive oxygen species (ROS). In response to drought stress, plants induce a series of physiological and biochemical changes, scavenging ROS. Among soil microbes, arbuscular mycorrhizal fungi (AMF) are found to be effective ameliorators of ROS under drought-stress conditions. However, the comprehensive roles of the oxidative stress ameliorators mediated by AMF in alleviating drought stress are not studied in detail. The present study aims to determine the oxidative stress ameliorators using meta-analysis highlighting AMF inoculation efficacy on drought stress alleviation. The results confirmed that AMF inoculation had a significant reduction in hydrogen peroxide (H2O2), malondialdehyde (MDA), and electrolyte leakage (EL). Nevertheless, proline accumulation was found to have a non-significant correlation with AMF inoculation. Further, carotenoids and soluble sugars increased positively in AMF-inoculated plants under drought stress and there was a subsequent reduction of abscisic acid (ABA). The results of the meta-analysis reveal the benefits of AMF inoculation with reduced H2O2 levels leading to reduced lipid peroxidation (MDA) and increased membrane stability (EL). Thus, the present assessment reveals the sequence of events involved in eliciting drought stress alleviation due to AMF inoculation.