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Publikation

Rekik, I.; Drira, N.; Grubb, C. D.; Elleuch, A.; Molecular characterization and evolution studies of a SERK like gene transcriptionally induced during somatic embryogenesis in Phoenix Dactylifera L v Deglet Nour Genetika 47, 323-337, (2015) DOI: 10.2298/GENSR1501323R

A somatic embryogenesis receptor kinase like (SERKL) cDNA, designated PhSERKL, was isolated from date palm (Phoenix Dactylifera L) using RACE PCR. PhSERKL protein shared all the characteristic domains of the SERK family, including five leucine-rich repeats, one proline-rich region motif, a transmembrane domain, and kinase domains. Phylogenetic analyses using PHYLIP and Notung 2.7 programs suggest that the SERK proteins of some plant species resulted from relatively ancient duplication events. We predict an ancestor protein of monocots and dicots SERK using FASTML program. Somatic embryogenic cultures of date palm were established following transfer of callus cultures to medium containing 2, 4-dichlorophenoxyacetic acid. The role of PhSERKL gene during establishment of somatic embryogenesis in culture was investigated using quantitative real-time PCR. PhSERKL gene was highly expressed during embryogenic competence acquisition and globular embryo formation in culture. Overall, levels of expression of PhSERKL gene were lower in nonembryogenic tissues and organs than in embryogenic callus.
Publikation

Rekik, I.; Chaâbene, Z.; Grubb, C. D.; Drira, N.; Cheour, F.; Elleuch, A.; In silico characterization and Molecular modeling of double-strand break repair protein MRE11 from Phoenix dactylifera v deglet nour Theor. Biol. Med. Model. 12, 23, (2015) DOI: 10.1186/s12976-015-0013-2

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).
Publikation

Elleuch, A.; Chaâbene, Z.; Grubb, D. C.; Drira, N.; Mejdoub, H.; Khemakhem, B.; Morphological and biochemical behavior of fenugreek (Trigonella foenum-graecum) under copper stress Ecotoxicol. Environ. Saf. 98, 46-53, (2013) DOI: 10.1016/j.ecoenv.2013.09.028

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 and Cu2+ 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.
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