Browsing by Author "Nada, Ahmed"

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Behavior of Tunisian Local Barley Accessions Under Progressive Water Deficit: Physiological and Biochemical Approaches
(Journal of Phytology, 2010) Abdellaoui, Raoudha; Tarhouni, Mohamed; Chaabane, Ramzi; Ben Naceur, M’barek; El Faleh, Mouldi; Abdelli, Chedly; Ramla, Delila; Nada, Ahmed; Sakr, Mahmoud; Ben Hmida, Jeannette
Leaf water potential, percentage of membrane integrity and pigments chlorophyll content provide information on plant water status, on cell membranes integrity and on its photosynthetic capacity particularly under water stress conditions. These parameters were used to differentiate the behavior of 14 local barley accessions subjected to various intensities of stress (one week, two weeks and three weeks). The Principal Component Analysis (PCA) of the collected data at the end of each week revealed that the accessions behavior varies with the water deficit period. In fact, some are tolerant during the first and/or second week of stress and subsequently they are affected with a very substantial reduction in their chlorophyll pigments and their percentage of membrane integrity after three weeks. Others appear to be sensitive during the first week of stress and became tolerant under severe stress. This tolerance is manifested by the maintenance of membrane integrity, high content of chlorophyll pigments, significant proline accumulation and important specific activity of peroxidases. The study also showed that the 14 accessions exhibit two behavior types: i) significant decrease in leaf water potential with proline accumulation (constitutive osmotic adjustment) to keep cells turgid and ii) trivial drop of leaf water potential (osmotic adjustment of adaptive type). Moreover, variability in the different accessions behavior to water deficit seems to be linked to their geographical origin especially that supposed tolerant accessions are mostly from South and Central Tunisia characterized by severe aridity.
A chloroplastic inner envelope membrane protease is essential for plant development
(FEBS letters, 2006) Bo¨lter, Bettina; Nada, Ahmed; Fulgosi, Hrovje; Soll, Ju¨rgen
Regulated intramembrane proteolysis (RIP) is a fundamental mechanism for controlling a wide range of cellular functions. Cleavage of membrane embedded proteins results in soluble fragments exerting their function, e.g., as transcription factors and thereby regulating gene expression. This process is highly conserved throughout all kingdom of life as are the involved proteases. RIP has been described in eukaryotes, bacteria and archea though until recently not in plant organelles. Here we describe a chloroplastic membrane protease which belongs to the conserved S2P family of membrane metallo proteases. We show that this protease is localized in the inner envelope membrane and is essential for plant development. It could function in a RIP like process regulating the concordant action in the plant cytosol, nucleus and plastids.
Genetic diversity analysis of North Africa’s barley using SSR markers
(Elsevier, 2012) Ben Naceur, Amani; Chaabane, Ramzi; El-Faleh, Mouldi; Abdelly, Chedly; Ramla, Dalila; Nada, Ahmed; Sakr, Mahmoud
It was demonstrated that some North Africa barley accessions have diverse tolerance sources for abiotic stresses and a good nutritional quality, but the studies done were incomplete since they were realized separately in each country apart. To implement a more complete analysis, 31 barley accessions originated from North Africa (Algeria, Tunisia and Egypt) were analyzed using 11 SSR markers selected from the seven barley linkage groups for studying the genetic diversity among these chosen barley accessions. Over the 11 SSR markers, a total of 478 reproducible bands were scored with an average of 2.13 alleles/primer and the average polymorphism information content of 0.5. Genetic distance analysis of the 31 accessions showed a large genetic diversity and high number of different groups. The most accessions are clustered according to their eco-geographical origin, according to their pedigree and agronomic characters or according to the caryopsis character (hulled or naked caryopsis). This high number of obtained groups is an invaluable aid in crop improvement strategies and confirms the opinion suggesting that North Africa could be a secondary center of origin of barley. The various growing conditions and the multiple uses of barley in each country may be the cause of the large variability of the barley germplasm in each region.
Inner envelope protein 32 is imported into chloroplasts by a novel pathway
(The Company of Biologists Ltd, 2004) Nada, Ahmed; Soll, Jürgen
The 32 kDa chloroplast inner envelope protein (IEP32) is imported into the organelle in the absence of a cleavable Nterminal pre-sequence. The ten N-terminal amino acids form an essential portion of this targeting information as deduced from deletion mutants. Recognition and translocation of IEP32 is not catalysed by the general chloroplast outer envelope translocon subunits Toc159, Toc75III and Toc34, because IEP32 import is neither inhibited by proteolytic removal of Toc34 and Toc159 nor by inhibition of the Toc75 import channel by CuCl2 or spermine. Import of IEP32 only requires ATP concentrations of below 20 µM indicating that stromal chaperones are not involved in the process, but that IEP32 might be directly inserted from the intermembrane space into the inner envelope by a so far unidentified pathway. IEP32 may require the assistance of Tic22, an intermembrane space translocon subunit for import as indicated by the presence of a chemical crosslinked product between both polypeptides.
Isolation and characterization of some drought-related ESTs from barley
(Academic Journals (Kenya), 2015) Radwan, Alzahraa; MI Abou Ali, Rania; Nada, Ahmed; Hashem, Wardaa; Assem, Shireen; Husein, Ebtissam
Drought is one of the main constraints facing crops and affecting their production. In a trial to investigate and understand drought effect, differential display experiments were performed where; about 107 DD-fragments have been isolated from wild barley plants subjected to drought treatment. These fragments were categorized according to their gene expression into four categories: 1) up regulated genes; 2) up and down regulated; 3) down regulated and 4) down and up regulated genes. The isolated fragments were cloned and sequenced. Sequence analysis using GeneBank database revealed that some fragments have significant similarities with starch branching enzyme I (sbeI) gene; glycosyl transferase family 1 gene; Retrotransposons Ty3-gypsy subclass; gag-polypeptide of LTR copia-type retroelement gene; IMP cyclohydrolase/phosphoribosylaminoimidazolecarboxamide formyltransferase and unknown proteins. Some other fragments have significant similarity with Triticum aestivum gene for TaAP2-B, complete cds and 3B chromosome, clone BAC TA3B63N2. These results indicate that starch metabolism, transposon elements and purine metabolism might have been affected by drought stress.
The Usage of Albedo Orange Methanol and Ethanol Extraction as Anticancer Agent
(Imperial Journal of Interdisciplinary Research, 2017) Moenes, Yara; Nada, Ahmed; Fahmy Mohamed, Aly
The present study aimed to evaluate the anticancer activity of methanol/ ethanol Orange Albedo extracts where test extracts showed antiproliferative activity. Also, the test extract viability % were concentration, IC50 value and cell type dependent. Also, there was a significant up / down regulation of pro/ anti apoptotic genes. Also the cell cycle profile indicated cell arrest at the G2 / M phase compared with the control accompanied with apoptotic profile significantly elevated than non treated cell control (P<0.05).