Cadmium toxicity induced changes in nitrogen management in Lycopersicon esculentum leading to a metabolic safeguard through an amino acid storage strategy.
Tomato (Lycopersicon esculentum) seedlings were grown in the presence of cadmium. After 1 week of Cd treatment, a sharp decline in biomass accumulation in the leaves and roots was observed, together with a decrease in the rate of photosynthetic activity due to both Rubisco and chlorophyll degradation and stomata closure. Cadmium induced a significant decrease in nitrate content and inhibition of the activities of nitrate reductase, nitrite reductase, glutamine synthetase (GS) and ferredoxin-glutamate synthase. An increase in NADH-glutamate synthase and NADH-glutamate dehydrogenase activity was observed in parallel. The accumulation of ammonium into the tissues of treated plants was accompanied by a loss of total protein and the accumulation of amino acids. Gln represented the major amino acid transported through xylem sap of Cd-treated and control plants. Cadmium treatment increased the total amino acid content in the phloem, maintaining Gln/Glu ratios. Western and Northern blot analysis of Cd-treated plants showed a decrease in chloroplastic GS protein and mRNA and an increase in cytosolic GS and glutamate dehydrogenase transcripts and proteins. An increase in asparagine synthetase mRNA was observed in roots, in parallel with a strong increase in asparagine. Taken together, these results suggest that the plant response to Cd stress involved newly induced enzymes dedicated to coordinated leaf nitrogen remobilization and root nitrogen storage.
Chaffei
Chiraz
C
Unité de Nutrition Azotée des Plantes, INRA, route de Saint Cyr, 78026 Versailles, France.
Pageau
Karine
K
Suzuki
Akira
A
Gouia
Houda
H
Ghorbel
Mohamed Habib
MH
Masclaux-Daubresse
Céline
C
D000594:Amino Acid Oxidoreductases / Q000378:metabolism; D000596:Amino Acids / Q000032:analysis*; D018533:Biomass; D002104:Cadmium / Q000494:pharmacology / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D018551:Solanum lycopersicum / Q000187:drug effects* / Q000378:metabolism; D009243:NAD / Q000378:metabolism; D050901:Nitrate Reductase; D009565:Nitrate Reductases / Q000378:metabolism; D009572:Nitrite Reductases / Q000378:metabolism; D009584:Nitrogen / Q000032:analysis / Q000378:metabolism*; D010788:Photosynthesis / Q000187:drug effects; D018515:Plant Leaves / Q000187:drug effects; D010940:Plant Proteins / Q000032:analysis; D018517:Plant Roots / Q000187:drug effects
D000596:Amino Acids; D010940:Plant Proteins; D002104:Cadmium; D009243:NAD; D000594:Amino Acid Oxidoreductases; C042233:glutamate synthase (ferredoxin); D009565:Nitrate Reductases; D009572:Nitrite Reductases; D050901:Nitrate Reductase; D005974:Glutamate-Ammonia Ligase; D009584:Nitrogen