NaCl stress effects on enzymes involved in nitrogen assimilation pathway in tomato "Lycopersicon esculentum" seedlings.
Tomato plants (Lycopersicon esculentum Mill, cv. Chibli F1) grown for 10 days on control medium were exposed to differing concentrations of NaCl (0, 25, 50, and 100mM). Increasing salinity led to a decrease of dry weight (DW) production and protein contents in the leaves and roots. Conversely, the root to shoot (R/S) DW ratio was increased by salinity. Na(+) and Cl(-) accumulation were correlated with a decline of K(+) and NO(3)(-) in the leaves and roots. Under salinity, the activities of nitrate reductase (NR, EC 1.6.6.1) and glutamine synthetase (GS, EC 6.3.1.2) were repressed in the leaves, while they were enhanced in the roots. Nitrite reductase (NiR, EC 1.7.7.1) activity was decreased in both the leaves and roots. Deaminating activity of glutamate dehydrogenase (GDH, EC 1.4.1.2) was inhibited, whereas the aminating function was significantly stimulated by salinity in the leaves and roots. At a high salt concentration, the nicotinamide adenine dinucleotide reduced (NADH)-GDH activity was stimulated concomitantly with the increasing NH(4)(+) contents and proteolysis activity in the leaves and roots. With respect to salt stress, the distinct sensitivity of the enzymes involved in nitrogen assimilation is discussed.
Debouba
Mohamed
M
Unité de Recherche 09-20: Nutrition, Métabolisme Azoté et Protéines de Stress, Faculté des Sciences de Tunis Département de Biologie, Université Tunis El Manar, Tunis 1060, Tunisie.
Gouia
Houda
H
Suzuki
Akira
A
Ghorbel
Mohamed Habib
MH
D002712:Chlorides / Q000378:metabolism; D005969:Glutamate Dehydrogenase / Q000378:metabolism; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D018551:Solanum lycopersicum / Q000201:enzymology* / Q000254:growth & development / Q000378:metabolism; D050901:Nitrate Reductase / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism; D009572:Nitrite Reductases / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D036226:Seedlings / Q000201:enzymology*; D012964:Sodium / Q000378:metabolism; D012965:Sodium Chloride / Q000378:metabolism*
D002712:Chlorides; D009566:Nitrates; D000644:Quaternary Ammonium Compounds; D012965:Sodium Chloride; D012964:Sodium; D005969:Glutamate Dehydrogenase; D009572:Nitrite Reductases; D050901:Nitrate Reductase; D010447:Peptide Hydrolases; D005974:Glutamate-Ammonia Ligase; D009584:Nitrogen; D011188:Potassium