الفهرس 
Literature REVIEWOnly 14 pages are availabe for public view
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Abstract
Callus was induced from seeds of tomato plant (Lycopersicon
esculentum cv. Super strain B) on MS medium supplemented with 0.5 mg/L
Naphthalene-acetic acid (NAA), 0.5 mg/L Indole-3-acetic acid (IAA), 2
mg/L Benzyl-aminopurine (BAP) and 2 mg/L Kinetin (Kn). This callus was
subjected to osmotic stress using elevated concentrations of mannitol (0.0,
50, 100, 150, 200, 250 and 300 mM). The sub-lethal concentration which
killed about 80% of callus cells (ID80) was determined to be 250 mM
mannitol. The remaining 20% of cells which survived the sub-lethal
concentration was selected visually and multiplied on the same medium
composition and are considered somaclonal variant cells and designated as
”selected callus line”. Experiments were conducted to compare different
metabolic activities of the selected callus line with the non-selected one
(control callus, 0.0 mannitol). Results showed reduction in fresh weight of
the selected line and non-significant reduction in relative water content
(RWC) of both callus lines. No significant difference was recorded in
electrolyte leakage percentage (EL%) or malondialdehyde content
(MDA) between both lines. An enhanced total antioxidant capacity (TAC),
peroxidase (POX) and ascorbate oxidase (ASO) activity and reduced
activity of superoxide dismutase (SOD) and ascorbate peroxidase (APX)
was found in the selected callus line. No change in the activity of catalase
(CAT) between both lines was noticed, however hydrogen peroxide content
(H2O2) increased in the selected line. The selected callus line accumulated
more ascorbic acid (AsA), GSH and abscisic acid (ABA), indicating that
the selected callus line tends to rely on the non-enzymatic antioxidant
mechanisms rather than enzymatic ones in spite of remarkable decrease in
total phenols content and lycopene concentration in the selected line.
Effect of osmotic stress, induced by mannitol, on stress-related
genes such as TAS14 gene and TSW12 gene was studied. The genomic
DNA of both the selected and non-selected callus line was extracted
according to CTAB protocol. The extracted genomic DNA was used for
Ploymerase Chain Reaction (PCR) using specific 1 set of primers covering
the entire coding sequence of TAS14 gene and TSW12 gene through the 2
exons then, the amplified product was sequencing and analyzed. The
analysis revealed the presence of novel and published mutations in TAS14
and TSW12 genes. Some of these mutations lead to changes in amino acid
sequence and consequently in protein structure.