Accumulation Of Mannitol Research Articles

Spore discharge associated with physiological quality variations and energy metabolism in harvested Lentinula edodes

As a sign of mushroom maturity, spore discharge continues accelerating in postharvest Lentinula edodes. However, the relationship between spore discharge quantity and both physiological quality and energy metabolism remains unclear. In this study, spore discharge intensity, the number of spores discharged per unit mass of fruiting body per unit time, was introduced to analyze the variations in physiological quality attributes and energy metabolism associated with spore discharge in harvested Lentinula edodes. The results demonstrated a correlation between increased spore discharge intensity and deteriorating weight loss, firmness, and browning of the fruiting bodies. Moreover, a positive relationship was observed between spore discharge intensity and mannitol, an osmotic substance released alongside spores. Mannitol metabolism is linked to glycolysis, suggesting that the accumulation of mannitol may enhance spore discharge. Significant correlations were identified between the total amount of spore discharge and H+-ATPase activity, as well as energy charge, which proved that higher levels of energy metabolism may promote spore discharge. Energy depletion was responsible for the deterioration in the physiological quality during this period. Collectively, a substantial amount of spore discharge needs to be supported by adequate osmotic substances and energy levels, and this result may provide a new perspective on the preservation of edible mushrooms. Delaying the peak of spore release and inhibiting the spore discharge intensity may be directions for maintaining the postharvest storage quality of edible mushrooms.

Mannitol mediates the mummification behavior of Thitarodes xiaojinensis larvae infected with Ophiocordyceps sinensis.

Parasites can facilitate their own spread and reproduction by manipulating insect hosts behavior, as seen in the interaction between Thitarodes xiaojinensis and Ophiocordyceps sinensis. Infection by O. sinensis leads to the mummification of T. xiaojinensis larvae, but the underlying mechanisms remain mysterious. The morphology of O. sinensis infected larvae and fungal growth were first observed. Subsequently, the metabolite changes in the larvae before and after infection with the fungus were analyzed by LC/MS and targeted metabolomics. The expression of mannitol-related genes was detected using RT-qPCR, and morphological changes in larvae were observed after injection of different concentrations of mannitol into the O. sinensis-infected larvae. Significant changes were found in phenotype, fungal morphology in hemocoel, larval hardness, and mannitol metabolites in infected, mummified 0 h larvae and larvae 5 days after mummification behavior. Surprisingly, the occurrence of mummification behavior was accompanied by fungal dimorphism, as well as the absence of mannitol in both infected and non-infected larvae, until the initial accumulation of mannitol and the expression of mannitol-associated genes occurred at the time of mummification behavior. The presence of mannitol may promote fungal dimorphism to mediate changes in fungal toxicity or resistance, leading to the end of the fungus-insect coexistence period and the incidence of mummification behavior. Furthermore, mannitol injections increase the mummification rate of the infected larvae without significant difference from the normal mummification phenotype. This finding suggests the importance of mannitol in the mummification of host larvae infected with O. sinensis.

Compatible solutes determine the heat resistance of conidia

BackgroundAsexually developed fungal spores (conidia) are key for the massive proliferation and dispersal of filamentous fungi. Germination of conidia and subsequent formation of a mycelium network give rise to many societal problems related to human and animal fungal diseases, post-harvest food spoilage, loss of harvest caused by plant-pathogenic fungi and moulding of buildings. Conidia are highly stress resistant compared to the vegetative mycelium and therefore even more difficult to tackle.ResultsIn this study, complementary approaches are used to show that accumulation of mannitol and trehalose as the main compatible solutes during spore maturation is a key factor for heat resistance of conidia. Compatible solute concentrations increase during conidia maturation, correlating with increased heat resistance of mature conidia. This maturation only occurs when conidia are attached to the conidiophore. Moreover, conidia of a mutant Aspergillus niger strain, constructed by deleting genes involved in mannitol and trehalose synthesis and consequently containing low concentrations of these compatible solutes, exhibit a sixteen orders of magnitude more sensitive heat shock phenotype compared to wild-type conidia. Cultivation at elevated temperature results in adaptation of conidia with increased heat resistance. Transcriptomic and proteomic analyses revealed two putative heat shock proteins to be upregulated under these conditions. However, conidia of knock-out strains lacking these putative heat shock proteins did not show a reduced heat resistance.ConclusionsHeat stress resistance of fungal conidia is mainly determined by the compatible solute composition established during conidia maturation. To prevent heat resistant fungal spore contaminants, food processing protocols should consider environmental conditions stimulating compatible solute accumulation and potentially use compatible solute biosynthesis as a novel food preservation target.

Exogenous Application of Indol-3-Acetic Acid and Salicylic Acid Improves Tolerance to Salt Stress in Olive Plantlets (Olea europaea L. Cultivar Picual) in Growth Chamber Environments

Salinity is one the most recurrent abiotic stresses worldwide and severely affects crop productivity in arid and semiarid environments. This research analyzed several plant growth regulators that could mitigate the effects of salinity on olive plants (Olea europaea L. cultivar Picual). Mist-rooted cuttings were grown in a growth chamber and pretreated with gibberellic acid (GA3), indole-3-acetic acid (IAA), salicylic acid (SA), and Kinetin by foliar spraying twice a week for three weeks. At the end of the pretreatment, the plants were exposed to 100 mM and 200 mM sodium chloride (NaCl) for six weeks. The results showed that plants pretreated with the plant growth regulators significantly increased their biomass under saline conditions. In addition, IAA and SA restricted the transport of sodium (Na+) ions from roots to leaves and improved the leaf potassium (K+)/Na+ ratio. IAA and SA favored proline, fructose, and mannitol accumulation in leaves at 100 mM and 200 mM NaCl, as did glucose at 200 mM NaCl. Salicylic acid and IAA increased pigments (chlorophylls and carotenoids) and polyamines accumulation under saline conditions. The findings of this study suggest that pretreatments with IAA and SA may be a highly effective way of increasing salt tolerance in olive plantlets.

Label-Free Assessment of Mannitol Accumulation Following Osmotic Blood-Brain Barrier Opening Using Chemical Exchange Saturation Transfer Magnetic Resonance Imaging.

Mannitol is a hyperosmolar agent for reducing intracranial pressure and inducing osmotic blood-brain barrier opening (OBBBO). There is a great clinical need for a non-invasive method to optimize the safety of mannitol dosing. The aim of this study was to develop a label-free Chemical Exchange Saturation Transfer (CEST)-based MRI approach for detecting intracranial accumulation of mannitol following OBBBO. In vitro MRI was conducted to measure the CEST properties of D-mannitol of different concentrations and pH. In vivo MRI and MRS measurements were conducted on Sprague-Dawley rats using a Biospec 11.7T horizontal MRI scanner. Rats were catheterized at the internal carotid artery (ICA) and randomly grouped to receive either 1 mL or 3 mL D-mannitol. CEST MR images were acquired before and at 20 min after the infusion. In vitro MRI showed that mannitol has a strong, broad CEST contrast at around 0.8 ppm with a mM CEST MRI detectability. In vivo studies showed that CEST MRI could effectively detect mannitol in the brain. The low dose mannitol treatment led to OBBBO but no significant mannitol accumulation, whereas the high dose regimen resulted in both OBBBO and mannitol accumulation. The CEST MRI findings were consistent with 1H-MRS and Gd-enhanced MRI assessments. We demonstrated that CEST MRI can be used for non-invasive, label-free detection of mannitol accumulation in the brain following BBBO treatment. This method may be useful as a rapid imaging tool to optimize the dosing of mannitol-based OBBBO and improve its safety and efficacy.

Differences in defence-related gene expression and metabolite accumulation reveal insights into the resistance of Greek grape wine cultivars to <i> Botrytis </i> bunch rot

Berries of 13 Greek grape wine cultivars were evaluated for resistance to Botrytis bunch rot. Artificial inoculations on detached berries revealed that the Greek cultivars tested varied regarding their susceptibility to Botrytis cinerea. Cultivar (cv.) “Limnio” was found to be highly resistant, while higher susceptibility was observed on berries of cv. “Roditis”. To determine the molecular basis of the observed resistance or susceptibility of cv. “Limnio” and “Roditis”, an expression analysis of 12 defence-related genes, was carried out on artificially inoculated berries of the two cultivars at different time points after inoculation. Gene expression measurements in the resistant cv. “Limnio” showed that the artificial inoculation with the pathogen triggered the induction of genes encoding pathogenesis-related (PR) proteins such as chitinases (CHIT), polygalacturonase-inhibiting protein (PGIP), serine proteinase inhibitor (PIN) and enzymes involved in phytoalexin synthesis such as phenylalanine ammonia-lyase (PAL) and stilbene synthase (STS). In contrast, on the susceptible cv. “Roditis”, most of the same genes were down-regulated. Metabolomic analysis revealed significant differences in the initial metabolic profiles of “Limnio” and “Roditis” berries. Furthermore, in response to inoculation, the abundance of several metabolites increased in the resistant cultivar indicating intensification of metabolic processes. Proline and mannitol accumulation, as well as the modification of metabolites related to phenylpropanoid and lignin biosynthesis, are among the major players in defence responses of the “Limnio” cultivar. The above findings enhance our understanding of the resistance of Greek grape wine cultivars to B. cinerea and, at the same time, lay the foundation for breeding wine grape cultivars in the future.

Drought stress improved the capacity of Rhizophagus irregularis for inducing the accumulation of oleuropein and mannitol in olive (Olea europaea) roots

Olive trees are often subjected to a prolonged dry season with low water availability, which induces oxidative stress. Arbuscular mycorrhizal (AM) symbioses can improve olive plant tolerance to water deficit. This study investigated several aspects related to drought tolerance in AM fungi olive plants. Non-AM and AM plants were grown under well-watered or drought-stressed conditions, and mycorrhizal growth response, neutral lipid fatty acid (NLFA)16:1ω5 and phospholipid fatty acid (PLFA) 16:1ω5 in roots (intraradical mycelium) and in soil (extraradical mycelium), carbohydrates (monosaccharides, disaccharides and polyols) and phenolic compounds (phenolic alcohols, flavonoids, lignans, secoiridoids and hydroxycinnamic acid derivatives) were determined. Results showed that the amounts of PLFA 16:1ω5 and NLFA 16:1ω5 were significantly influenced by drought stress conditions. The NLFA 16:1ω5/PLFA 16:1ω5 ratio showed a dramatic decrease (−62%) with the application of water deficit stress, indicating that AM fungi allocated low carbon to storage structures under stress conditions. Mannitol and verbascoside are the main compounds detected in the roots of well-watered plants, whereas oleuropein and mannitol are the main compounds differentially accumulated in the roots of water-stressed plants. The oleuropein/verbascoside ratio increased in the case of drought-stressed AM plants by 30%, while the mannitol/oleuropein ratio was decreased by 46%, when compared to the non-AM stressed plants. Mycorrhization therefore oriented the flux toward the biosynthetic pathway of oleuropein and the data suggest that sugar and phenolic compound metabolism may have been redirected to the formation of oleuropein in roots of AM stressed plants, that may underlie their enhanced tolerance to drought stress.

Retracted: Overexpression of Bacterial mtlD Gene in Peanut Improves Drought Tolerance through Accumulation of Mannitol.

[This retracts the article DOI: 10.1155/2014/125967.].

Transcriptome sequencing of Saccharina japonica sporophytes during whole developmental periods reveals regulatory networks underlying alginate and mannitol biosynthesis

BackgroundAlginate is an important cell wall component and mannitol is a soluble storage carbon substance in the brown seaweed Saccharina japonica. Their contents vary with kelp developmental periods and harvesting time. Alginate and mannitol regulatory networks and molecular mechanisms are largely unknown.ResultsWith WGCNA and trend analysis of 20,940 known genes and 4264 new genes produced from transcriptome sequencing of 30 kelp samples from different stages and tissues, we deduced that ribosomal proteins, light harvesting complex proteins and “imm upregulated 3” gene family are closely associated with the meristematic growth and kelp maturity. Moreover, 134 and 6 genes directly involved in the alginate and mannitol metabolism were identified, respectively. Mannose-6-phosphate isomerase (MPI2), phosphomannomutase (PMM1), GDP-mannose 6-dehydrogenase (GMD3) and mannuronate C5-epimerase (MC5E70 and MC5E122) are closely related with the high content of alginate in the distal blade. Mannitol accumulation in the basal blade might be ascribed to high expression of mannitol-1-phosphate dehydrogenase (M1PDH1) and mannitol-1-phosphatase (M1Pase) (in biosynthesis direction) and low expression of mannitol-2-dehydrogenase (M2DH) and Fructokinase (FK) (in degradation direction). Oxidative phosphorylation and photosynthesis provide ATP and NADH for mannitol metabolism whereas glycosylated cycle and tricarboxylic acid (TCA) cycle produce GTP for alginate biosynthesis. RNA/protein synthesis and transportation might affect alginate complex polymerization and secretion processes. Cryptochrome (CRY-DASH), xanthophyll cycle, photosynthesis and carbon fixation influence the production of intermediate metabolite of fructose-6-phosphate, contributing to high content of mannitol in the basal blade.ConclusionsThe network of co-responsive DNA synthesis, repair and proteolysis are presumed to be involved in alginate polymerization and secretion, while upstream light-responsive reactions are important for mannitol accumulation in meristem of kelp. Our transcriptome analysis provides new insights into the transcriptional regulatory networks underlying the biosynthesis of alginate and mannitol during S. japonica developments.

Engineering Oleaginous Yeast as the Host for Fermentative Succinic Acid Production From Glucose.

Oleaginous yeast Yarrowia lipolytica is a prospective host for production of succinic acid. The interruption of tricarboxylic acid cycle through succinate dehydrogenase gene (SDH) deletion was reported to result in strains incapable of glucose utilization and this ability had to be restored by chemical mutation or long adaptive laboratory evolution. In this study, a succinate producing strain of Y. lipolytica was engineered by truncating the promoter of SDH1 gene, which resulted in 77% reduction in SDH activity but did not impair the ability of the strain to grow on glucose. The flux toward succinic acid was further improved by overexpressing the genes in the glyoxylate pathway and the oxidative TCA branch, and expressing phosphoenolpyruvate carboxykinase from Actinobacillus succinogenes. A short adaptation on glucose reduced the lag phase of the strain and increased its tolerance to high glucose concentrations. The resulting strain produced 7.8 ± 0.0 g/L succinic acid with a yield of 0.105 g/g glucose in shake flasks without pH control, while mannitol (11.8 ± 0.8 g/L) was the main by-product. Further investigations showed that mannitol accumulation was caused by low pH stress and buffering the fermentation medium eliminated mannitol formation. In a fed-batch bioreactor in mineral medium at pH 5, at which point according to Ka values of succinic acid, the major fraction of product was in acidic form rather than dissociated form, the strain produced 35.3 ± 1.5 g/L succinic acid with 0.26 ± 0.00 g/g glucose yield.

Characterization of gfdB, putatively encoding a glycerol 3-phosphate dehydrogenase in Aspergillus nidulans

The genome of Aspergillus nidulans accommodates two glycerol 3-phosphate dehydrogenase genes, gfdA and gfdB. Previous studies confirmed that GfdA is involved in the osmotic stress defence of the fungus. In this work, the physiological role of GfdB was characterized via the construction and functional characterization of the gene deletion mutant ΔgfdB. Unexpectedly, ΔgfdB strains showed oxidative stress sensitivity in the presence of a series of well-known oxidants including tert-butyl-hydroperoxide (tBOOH), diamide as well as hydrogen peroxide. Moderate sensitivity of the mutant towards the cell wall stress inducing agent CongoRed was also observed. Hence, both Gfd isoenzymes contributed to the environmental stress defence of the fungus but their functions were stress-type-specific. Furthermore, the specific activities of certain antioxidant enzymes, like catalase and glutathione peroxidase, were lower in ΔgfdB hyphae than those recorded in the control strain. As a consequence, mycelia from ΔgfdB cultures accumulated reactive species at higher levels than the control. On the other hand, the specific glutathione reductase activity was higher in the mutant, most likely to compensate for the elevated intracellular oxidative species concentrations. Nevertheless, the efficient control of reactive species failed in ΔgfdB cultures, which resulted in reduced viability and, concomitantly, early onset of programmed cell death in mutant hyphae. Inactivation of gfdB brought about higher mannitol accumulation in mycelia meanwhile the erythritol production was not disturbed in unstressed cultures. After oxidative stress treatment with tBOOH, only mannitol was detected in both mutant and control mycelia and the accumulation of mannitol even intensified in the ΔgfdB strain.

Efficient D-threitol production by an engineered strain of Yarrowia lipolytica overexpressing xylitol dehydrogenase gene from Scheffersomyces stipitis

D-threitol (hereinafter as threitol) is a diastereoisomer of erythritol with wider applications in green chemistry, food, pharmaceutical, and medicine. Herein, xylitol dehydrogenase from Scheffersomyces stipitis CBS 6054 was demonstrated able to catalyze highly efficient threitol formation from erythritol with erythrulose as an intermediate. When the corresponding gene Ss-XDH was overexpressed in the erythritol-producing Yarrowia lipolytica strain CGMCC7326, threitol was produced with a titer of 112 g·L−1 and yield of 0.37 from glucose. Unexpectedly, gene encoding mannitol dehydrogenase was upregulated in the threitol producing stain, leading to mannitol accumulation in the culture broth. In order to eliminate this byproduct and coproduced erythritol, a second process step based on the culture of Candida parapsilosis was developed to facilitate subsequent threitol purification. This is the first report to efficiently biosynthesize threitol from glucose through the fermentation process by an engineered Y. lipolytica and wild-type Candida parapsilosis.

The polyubiquitin gene MrUBI4 is required for conidiation, conidial germination, and stress tolerance in the filamentous fungus Metarhizium robertsii.

The polyubiquitin gene is a highly conserved open reading frame that encodes different numbers of tandem ubiquitin repeats from different species, which play important roles in different biological processes. Metarhizium robertsii is a fungal entomopathogen that is widely applied in the biological control of pest insects. However, it is unclear whether the polyubiquitin gene is required for fungal development, stress tolerance, and virulence in the entomopathogenic fungus. In the present study, the polyubiquitin gene (MrUBI4, MAA_02160) was functionally characterized via gene deletion in M. robertsii. Compared to the control strains, the MrUBI4 deletion mutant showed delayed conidial germination and significantly decreased conidial yields (39% of the wild-type 14 days post-incubation). Correspondingly, the transcript levels of several genes from the central regulatory pathways associated with conidiation, including brlA, abaA, and wetA, were significantly downregulated, which indicated that MrUBI4 played an important role in asexual sporulation. Deletion of MrUBI4 especially resulted in increased sensitivity to ultraviolet (UV) and heat-shock stress based on conidial germination analysis between mutant and control strains. The significant increase in sensitivity to heat-shock was accompanied with reduced transcript levels of genes related to heat-shock protein (hsp), trehalose, and mannitol accumulation (tps, tpp, nth, and mpd) in the MrUBI4 deletion mutant. Deletion of MrUBI4 has no effect on fungal virulence. Altogether, MrUBI4 is involved in the regulation of conidiation, conidial germination, UV stress, and heat-shock response in M. robertsii.

Metabolomic Profiling and Lipid Composition of Arctic and Antarctic Strains of Micromycetes Geomyces pannorum and Thelebolus microsporus Grown at Different Temperatures

Adaptive reactions of Arctic and Antarctic strains of psychrophilic micromycetes Geomyces pannorum and Thelebolus microsporus to growth within a broad temperature range were studied. Adaptation of these species to different temperatures was found to result from both morphological and biochemical changes, including changes in the concentration of small molecules and lipid membrane components. These biochemical, morphological, and physiological mechanisms exhibited the patterns common to all strains, as well as species and strain differences. The general patterns included temperature-dependent changes in amounts of monosaccharides, some disaccharides, and free linoleic and linolenic acids. The differences between the Arctic and Antarctic strains were mainly associated with the differences in lipid composition, while interspecies differences resulted from metabolomic modifications. Antarctic strains showed lower ability to survive elevated temperatures, which correlated with weaker manifestation of the lipid-dependent adaptive mechanisms compared to the Arctic strains. Among the interstrain differences, higher growth parameters and mannitol accumulation were found in the Arctic isolates. Adaptation of T. microsporus was characterized by more diverse changes in the concentrations of small organic molecules in the metabolome profile and by pronounced changes in mycelial morphology. The results of metabolomic analysis and their subsequent treatment by the methods of multivariant statistics supported the suggestion of higher dispersion of metabolomic characteristics under unfavorable conditions and of lower dispersion of metabolomic data under optimal conditions.

Combinatorial impact of osmotic and heat shocks on the composition of membrane lipids and osmolytes in Aspergillus niger.

The combinatorial action of osmotic (OS) and heat (HS) shocks on the composition of soluble cytosol carbohydrates and membrane lipids was studied. For the first time it was demonstrated that the combinatorial effect of these shocks led to the non-additive response - an increase in the trehalose level, characteristic for HS, but at the same time suppression of glycerol production, uncharacteristic of the OS response. In addition, combinatorial action resulted in a new effect - increase in the mannitol level, which was not typical for the individual HS or OS responses. On the contrary, a general pattern of change was observed in the composition of membrane lipids in response to both individual HS and OS, and their combinations, which was a twofold increase in the proportion of phosphatidic acids. At the same time, the mechanism of alteration in the degree of unsaturation of membrane phospholipids was not involved in adaptation. The response to combinatorial shocks includes the accumulation of trehalose and mannitol, and increase in the proportion of phosphatidic acids in membrane lipids.

Tolerance of Transplastomic Tobacco Plants Overexpressing a Theta Class Glutathione Transferase to Abiotic and Oxidative Stresses

Chloroplasts are organelles subjected to extreme oxidative stress conditions. Biomolecules produced in the chloroplasts act as signals guiding plant metabolism toward stress tolerance and play a major role in regulating gene expression in the nucleus. Herein, we used transplastomic plants as an alternative approach to expression of transgenes in the nucleus for conferring stress tolerance to abiotic stresses and herbicides. To investigate the morphophysiological and molecular mechanisms and the role of plastid expressed GSTs in tobacco stress detoxification and stress tolerance, we used transplastomic tobacco lines overexpressing a theta class glutathione transferase (GST) in chloroplasts. The transplastomic plants were tested under drought (0, 100, and 200 mM mannitol) and salinity (0, 150, and 300 mM NaCl) in vitro, and under herbicide stress (Diquat). Our results suggest that ptAtGSTT lines were tolerant to herbicide-induced oxidative and salinity stresses and showed enhanced response tolerance to mannitol-induced osmotic stress compared to WT plants. Overexpression of the Arabidopsis thaliana AtGSTT in the chloroplasts resulted in enhanced photo-tolerance and turgor maintenance under stress. Whole-genome transcriptome analysis revealed that genes related to stress tolerance, were upregulated in ptAtGSTT2a line under both control and high mannitol stress conditions. Transplastomic plants overexpressing the ptAtGSTT2a in the chloroplast showed a state of acclimation to stress, as only limited number of genes were upregulated in the ptAtGSTT2a transplastomic line compared to WT under stress conditions while at the same time genes related to stress tolerance were upregulated in ptAtGSTT2a plants compared to WT in stress-free conditions. In parallel, the metabolic profile indicated limited perturbations of the metabolic homeostasis in the transplastomic lines and greater accumulation of mannitol, and soluble sugars under high mannitol stress. Therefore, transplastomic lines seem to be in a state of acclimation to stress under stress-free conditions, which was maintained even under high mannitol stress. The results help to elucidate the role of GSTs in plant abiotic stress tolerance and the underlying mechanisms of the GSTs expressed in the chloroplast, toward environmental resilience of cultivated crops.

Possible source of the high UV-B and heat tolerance of Metarhizium acridum (isolate ARSEF 324).

The isolate ARSEF 324 of Metarhizium acridum is very tolerant to UV-B radiation and heat, but the intrinsic traits behind the extreme tolerance of this isolate to both stress conditions have not been elucidated. Because trehalose and mannitol are documented stress reducers in fungi, we investigated the accumulation of these compounds in conidia of ARSEF 324 compared with the accumulation of these two compounds in conidia of M. robertsii (ARSEF 23 and ARSEF 2575), which are considerably more susceptible to UV-B radiation and heat than ARSEF 324. Conidia of ARSEF 324 produced on potato dextrose agar plus yeast extract accumulated two-fold more trehalose and mannitol than conidia of ARSEF 23 and ARSEF 2575 produced on the same medium. The high accumulation of trehalose and mannitol in conidia of ARSEF 324 suggests one mechanism that it uses to attain its high tolerance to UV-B radiation and heat.

Transgenic Peanut (Arachis hypogaea L.) Overexpressing mtlD Gene Showed Improved Photosynthetic, Physio-Biochemical, and Yield-Parameters under Soil-Moisture Deficit Stress in Lysimeter System.

Peanut, an important oilseed crop, frequently encounters drought stress (DS) during its life cycle. In this study, four previously developed mtlD transgenic (T) peanut lines were used for detailed characterization under DS, at the reproductive stage using lysimeter system under controlled greenhouse conditions. In dry-down experiments, T lines maintained better photosynthetic machinery, such as, photosynthesis rate, stomatal conductance, transpiration rate, and SPAD (Soil-Plant Analyses Development) values, and had lower oxidative damage, including lipid membrane peroxidation and hydrogen peroxide and superoxide radical accumulation than WT, when exposed to 24 days of DS. WT plants had a more negative water potential (WP; up to −3.22 MPa) than T lines did (−2.56 to −2.71 MPa) at day 24 of DS treatment. During recovery, T lines recovered easily whereas 67% of WT plants failed to recover. In T lines, the rate of photosynthesis strongly and positively correlated with the transpiration rate (r = 0.92), RWC (r = 0.90), WP (r = 0.86), and total chlorophyll content (r = 0.75), suggesting its strong correlation with water retention-related parameters. Furthermore, yield parameters such as, pod weight and harvest index of T lines were up to 2.19 and 1.38 times more than those of WT plants, respectively. Thus, the significantly better performance of mtlD T peanut lines than of WT plants under DS could be attributed to the accumulation of mannitol, which in turn helped in maintaining the osmoregulation and ROS scavenging activity of mannitol and ultimately conferred water-economizing capacity and higher yield in T lines than in WT plants.

Cloning of a functional mannose-6-phosphate reductase (M6PR) gene homolog from Egyptian celery plants (Apium graveolens): overexpression in non-mannitol producing plants resulted in mannitol accumulation in transgenic individuals.

Salinity is a major limiting factor affecting crops production, survival and distribution worldwide. Engineering dehydration stress tolerance in commercial crops is a trait of economic importance, especially in saline-affected areas. In this work, we are reporting the cloning of the M6PR gene homolog (encoding a key enzyme, mannose-6-phosphate reductase, for mannitol biosynthesis in celery) from Egyptian celery plants. Using RACE technique, the full-length Egyptian-M6PR gene (1333bp) was cloned into pRI-201AN plant expression vector. Analysis of the cloned gene revealed that both American and Egyptian clones had both start and stop codons in frame and was found to be 930 base long. The newly cloned EM6PR gene was found to be 126 base longer than its American counterpart at the non-coding region. Six differences at nucleotide level between the Egyptian and American sequences were observed, three of which in the coding region resulting in three polymorphic amino acids differences (tryptophan vs. leucine, glutamine vs. histidine and isoleucine vs. leucine). The newly cloned gene was introduced to tobacco via Agrobacterium and PCR analysis of T0 plants indicated the presence of the EM6PR gene into 10 out of 38 tobacco individuals. Moreover, RT-PCR analysis confirmed the presence of EM6PR transcripts in 9 out of the 10 PCR positive plants. GC/MS analysis of some RT positive individuals indicated the accumulation of mannitol in transgenics tobacco, while mannitol was absent in non-transgenic controls.

Early Embryogenesis of Brown Alga Fucus vesiculosus L. is Characterized by Significant Changes in Carbon and Energy Metabolism.

Brown algae have an important role in marine environments. With respect to their broad distribution and importance for the environment and human use, brown algae of the order Fucales in particular became a model system for physiological and ecological studies. Thus, several fucoids have been extensively studied for their composition on the molecular level. However, research of fucoid physiology and biochemistry so far mostly focused on the adult algae, so a holistic view on the development of these organisms, including the crucial first life stages, is still missing. Therefore, we employed non-targeted metabolite profiling by gas chromatography coupled to mass spectrometry to create a non-biased picture of the early development of the fucoid alga Fucus vesiculosus. We found that embryogenic physiology was mainly dominated by a tight regulation of carbon and energy metabolism. The first dramatic changes of zygote metabolism started within 1 h after fertilization, while metabolism of 6–9 days old embryos appeared already close to that of an adult alga, indicated by the intensive production of secondary metabolites and accumulation of mannitol and citric acid. Given the comprehensive description and analysis we obtained in our experiments, our results exhibit an invaluable resource for the design of further experiments related to physiology of early algal development.