Noureddine Drira

Comparative transcriptome and metabolite analysis of oil palm and date palm mesocarp that differ dramatically in carbon partitioning

Oil palm can accumulate up to 90% oil in its mesocarp, the highest level observed in the plant kingdom. In contrast, the closely related date palm accumulates almost exclusively sugars. To gain insight into the mechanisms that lead to such an extreme difference in carbon partitioning, the transcriptome and metabolite content of oil palm and date palm were compared during mesocarp development. Compared with date palm, the high oil content in oil palm was associated with much higher transcript levels for all fatty acid synthesis enzymes, specific plastid transporters, and key enzymes of plastidial carbon metabolism, including phosphofructokinase, pyruvate kinase, and pyruvate dehydrogenase. Transcripts representing an ortholog of the WRI1 transcription factor were 57-fold higher in oil palm relative to date palm and displayed a temporal pattern similar to its target genes. Unexpectedly, despite more than a 100-fold difference in flux to lipids, most enzymes of triacylglycerol assembly were expressed at similar levels in oil palm and date palm. Similarly, transcript levels for all but one cytosolic enzyme of glycolysis were comparable in both species. Together, these data point to synthesis of fatty acids and supply of pyruvate in the plastid, rather than acyl assembly into triacylglycerol, as a major control over the storage of oil in the mesocarp of oil palm. In addition to greatly increasing molecular resources devoted to oil palm and date palm, the combination of temporal and comparative studies illustrates how deep sequencing can provide insights into gene expression patterns of two species that lack genome sequence information.

Interspecific potato somatic hybrids between Solanum berthaultii and Solanum tuberosum L. showed recombinant plastome and improved tolerance to salinity

In this study three somatic hybrid lines originating from protoplast fusion between Solanum tuberosum cv. BF15 and Solanum berthaultii were subjected to a detailed molecular analysis using the I-SSR-PCR technique based on 5′-anchored microsatellite primers. The data obtained revealed a polymorphism between the different lines, suggesting that they correspond to symmetric hybrids. The analysis of chloroplast genome of these hybrids showed that they are resulting from a recombination between parental plastomes. When transferred to a greenhouse, these hybrid lines displayed an improved vigour compared to the cultivated potato BF15 parent. Indeed, an important growth rate and high tuber yield and weight were obtained for these hybrids compared to the parent. Some of these hybrids showed also an improved ion homeostasis control and they seem to display a better tolerance to salt stress compared to the potato BF15 parent.

Morphological and biochemical behavior of fenugreek (Trigonella foenum-graecum) under copper stress.

The effects of copper on germination and growth of fenugreek (Trigonella foenum-graecum) was investigated separately using different concentrations of CuSO₄. The germination percentage and radical length had different responses to cupric ions: the root growth increased with increasing copper concentration up to 1 mM Cu²⁺ and was inhibited thereafter. In contrast, the germination percentage was largely unaffected by concentrations of copper below 10 mM. The reduction in root growth may have been due to inhibition of hydrolytic enzymes such as amylase. Indeed, the average total amylolytic activity decreased from the first day of treatment with [Cu²⁺] greater than 1 mM. Furthermore, copper affected various plant growth parameters. Copper accumulation was markedly higher in roots as compared to shoots. While both showed a gradual decrease in growth, this was more pronounced in roots than in leaves and in stems. Excess copper induced an increase in the rate of hydrogen peroxide (H₂O₂) production and lipid peroxidation in all plant parts, indicating oxidative stress. This redox stress affected leaf chlorophyll and carotenoid content which decreased in response to augmented Cu levels. Additionally, the activities of proteins involved in reactive oxygen species (ROS) detoxification were affected. Cu stress elevated the ascorbate peroxidase (APX) activity more than two times at 10 mM CuSO₄. In contrast, superoxide dismutase (SOD) and catalase (CAT) levels showed only minor variations, only at 1 mM Cu²⁺. Likewise, total phenol and flavonoid contents were strongly induced by low concentrations of copper, consistent with the role of these potent antioxidants in scavenging ROS such as H₂O₂, but returned to control levels or below at high [Cu²⁺]. Taken together, these results indicate a fundamental shift in the plant response to copper toxicity at low versus high concentrations.

Cold hardening and sucrose treatment improve cryopreservation of date palm meristems

Date palm (Phoenix dactylifera L.) cv. Khenizi caulogenic meristems were initiated from achlorophyllous leaves excised from in vitro shoot cultures and then proliferated on a specific culture medium supplemented with 70 g dm−3 sucrose. Regeneration rates obtained when using standard vitrification, droplet-vitrification, and encapsulation-vitrification protocols reached 26.7, 60.0, and 40.0 %, respectively. Only explants smaller than 3 mm in diameter were found to survive cryogenic treatments. Sucrose preculture, cold hardening and loading solution pretreatments showed significant effects on regeneration rates. Moreover, our results indicate that both sucrose preculture and cold acclimation of explants increased proline content. Cryopreservation of date palm tissue with high proliferation capacity can directly benefit large scale micropropagation projects.

Evaluation of anti-diabetic and anti-tumoral activities of bioactive compounds from Phoenix dactylifera L's leaf: In vitro and in vivo approach.

Among various chronic disorders, cancer and diabetes mellitus are the most common disorders. This study was designed to evaluate the effectiveness of hydroalcoholic extract of Phoenix dactylifera L. leaves (HEPdL) in animal models of type II diabetes in vitro/in vivo and in a human melanoma-derived cell line (IGR-39). A liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis was also performed to determine the amount of phenolic and flavonoid compounds in this plant. The physicochemical results by LC-MS/MS analysis of HEPdL showed the presence of 10 phenolic compounds. The in vitro study showed that the extract exhibited a more specific and potent inhibitor of α-glucosidase than α-amylase with an IC50 value of 20±1μg/mL and 30±0.8μg/mL, respectively. More importantly, the in vivo study of the postprandial hyperglycemia activity with (20mg/kg) of HEPdL showed a decrease in plasma glucose levels after 60min in resemblance to the glucor (acarbose) (50mg/kg) effect. The oral administration of HEPdL (20mg/kg) in alloxan-induced diabetic mices for 28days showed a more significant anti-diabetic activity than that of the drug (50mg/kg). Moreover, cytotoxicity effects of HEPdL in IGR-39 cancer cell lines were tested by MTT assay. This extract was effective in inhibiting cancer cells growth (IGR-39) at dose 35 and 75μg/mL. These results confirm ethnopharmacological significance of the plant and could be taken further for the development of an effective pharmaceutical drug against diabetes and cancer.

Phenolic Contents and Antioxidant Activities of Date Palm (Phoenix dactylifera L.) Leaves

The antioxidant capacity and phenolic content of three varieties of Phoenix dactylifera leaves, namely Deglet Nour, Medjhoul, and Barhee, were studied. The antioxidant activities of extracts of different leaf varieties obtained with solvents of different polarity were investigated using assays of 2, 2-diphenyl-2-picrymhydrasyl hydrate radical-scavenging activity, total phenolics and flavonoids amount, condensed tannins, reducing power, and total antioxidant capacity. The results showed that all the extracts exhibited antioxidant and radical-scavenging activities at different magnitudes and potency. The decreasing order of antioxidant and radical-scavenging activities among the extracts assayed were found to be methanol (MeOH) fraction > ethyl acetate fraction > hexane fraction > water extract. Correlation analysis indicated that there is a linear relationship between antioxidant potency, free radical-scavenging ability, and the content of phenolic and flavonoids compounds of Phoenix dactylifera leaf extracts. These results showed that Phoenix dactylifera leaf extracts are a valuable natural antioxidant, which can be applied in both healthy medicine and food industry and biotechnology.

Extraction optimization and in vitro and in vivo anti-postprandial hyperglycemia effects of inhibitor from Phoenix dactylifera L. parthenocarpic fruit

Phoenix dactylifera L. plays an important role in social, economic, and ecological Tunisian sectors. Some date palms produce parthenocarpic fruit named Sish. The aqueous ethanolic extract from P. dactylifera parthenocarpic dates demonstrated a potent inhibition of the enzymes related to type II diabetes. In this work, extraction optimization of amylase inhibitors was carried out using Box-Behnken Design. Bioactivity-guided fractionation of the 70% aqueous ethanol extract was performed to identify the active compounds. The physicochemical results by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis showed the presence of 13 phenolic compounds. The in vitro study showed that the extract exhibited a more specific inhibitor of α-glucosidase than α-amylase with an IC50 value of 0.6 and 2.5mg/mL, respectively. The in vivo study of this extract effect on the postprandial hyperglycemia activity showed a decrease in plasma glucose levels after 30min stronger than the Acarbose effect. These results confirmed the anti-postprandial hyperglycemia activity of the aqueous ethanolic extract from P. dactylifera parthenocarpic dates, which could lend support for its pharmaceutical use.

Extraction, partial purification and characterization of amylase from parthenocarpic date (P. dactylifera): effect on the cake quality

BACKGROUND Phoenix dactylifera L. plays an important role in social, economic and ecological Tunisian sectors. Some date palms produce parthenocarpic fruit named Sish. The objective of the present study was to extract biomolecules from parthenocarpic fruit by producing value-added products from the fruits. RESULTS The extraction of amylolytic activity from parthenocarpic fruit (AmyPF) was optimized using Box-Behnken design (BBD). Partial purification of about 250-fold with an activity yield of 47% was achieved. The amylase exhibited a specific activity of 80 U mg-1 protein. The optimum pH and temperature for enzyme activity were 5 and 55 °C respectively. The enzyme was highly active over a wide range of pH (5-10), and significant stabilization was observed at 60 °C. The purified enzyme belongs to the exo type of amylases. Given the economic and industrial relevance of amylases used in the food industry, three different concentrations of AmyPF (0.007, 0.014 and 0.018 U g-1 ) were incorporated into a cake formulation, resulting in a decrease in density, moisture retention and water activity and an increase in hardness. CONCLUSION The beneficial effect of AmyPF on the technological characteristics of cakes was confirmed by sensory evaluation.

In silico characterization and Molecular modeling of double-strand break repair protein MRE11 from Phoenix dactylifera v deglet nour

BackgroundDNA double-strand breaks (DSBs) are highly cytotoxic and mutagenic. MRE11 plays an essential role in repairing DNA by cleaving broken ends through its 3′ to 5′ exonuclease and single-stranded DNA endonuclease activities.MethodsThe present study aimed to in silico characterization and molecular modeling of MRE11 from Phoenix dactylifera L cv deglet nour (DnMRE11) by various bioinformatic approaches. To identify DnMRE11 cDNA, assembled contigs from our cDNA libraries were analysed using the Blast2GO2.8 program.ResultsThe DnMRE11 protein length was 726 amino acids. The results of HUMMER show that DnMRE11 is formed by three domains: the N-terminal core domain containing the nuclease and capping domains, the C-terminal half containing the DNA binding and coiled coil region. The structure of DnMRE11 is predicted using the Swiss-Model server, which contains the nuclease and capping domains. The obtained model was verified with the structure validation programs such as ProSA and QMEAN servers for reliability. Ligand binding studies using COACH indicated the interaction of DnMRE11 protein with two Mn2+ ions and dAMP. The ConSurf server predicted that residues of the active site and Nbs binding site have high conservation scores between plant species.ConclusionsA model structure of DnMRE11 was constructed and validated with various bioinformatics programs which suggested the predicted model to be satisfactory. Further validation studies were conducted by COACH analysis for active site ligand prediction, and revealed the presence of six ligands binding sites and two ligands (2 Mn2+ and dAMP).

Antioxidant, Anti-Inflammatory, and Antitumoral Effects of Aqueous Ethanolic Extract from Phoenix dactylifera L. Parthenocarpic Dates

The aim of this study was to evaluate the antioxidant, the anti-inflammatory, and the antitumoral activities of the aqueous ethanolic extract from Phoenix dactylifera L. parthenocarpic dates. The antioxidant activity was carried using DPPH radical scavenging activity. The result showed that parthenocarpic dates had strongly scavenging activity on DPPH reaching 94% with an IC50 value of 0.15 ± 0.011 mg/mL (p < 0.05). The anti-inflammatory potential was determined by the inhibitory effect of the aqueous ethanolic extract on phospholipase A2 activity as well as on carrageenan-induced paw oedema in mice. The in vitro study showed that the extract inhibited the phospholipase A2 activity with an IC50 value of 130 μg/mL and the in vivo study showed a significantly decrease in the paw oedema after 1 h compared to the control group. Finally, the antiproliferative activity of the aqueous ethanolic extract was assessed by MTT test against MCF-7 and MDA-MB-231 cancer cell lines. This extract was effective in inhibiting MDA-MB-231 and MCF-7 cancer cells growth with IC50 values of 8 and 18 mg/mL, respectively, after 72 h treatment. These results confirm the ethnopharmacological significance of Phoenix dactylifera L. parthenocarpic dates, which could add support for its pharmaceutical use.