Iron deficiency affects nitrogen metabolism in cucumber (Cucumis sativus L.) plants.
BACKGROUND
Nitrogen is a principal limiting nutrient in plant growth and development. Among factors that may limit NO3- assimilation, Fe potentially plays a crucial role being a metal cofactor of enzymes of the reductive assimilatory pathway. Very few information is available about the changes of nitrogen metabolism occurring under Fe deficiency in Strategy I plants. The aim of this work was to study how cucumber (Cucumis sativus L.) plants modify their nitrogen metabolism when grown under iron deficiency.


RESULTS
The activity of enzymes involved in the reductive assimilation of nitrate and the reactions that produce the substrates for the ammonium assimilation both at root and at leaf levels in Fe-deficient cucumber plants were investigated. Under Fe deficiency, only nitrate reductase (EC 1.7.1.1) activity decreased both at the root and leaf level, whilst for glutamine synthetase (EC 6.3.1.2) and glutamate synthase (EC 1.4.1.14) an increase was found. Accordingly, the transcript analysis for these enzymes showed the same behaviour except for root nitrate reductase which increased. Furthermore, it was found that amino acid concentration greatly decreased in Fe-deficient roots, whilst it increased in the corresponding leaves. Moreover, amino acids increased in the xylem sap of Fe-deficient plants.


CONCLUSIONS
The data obtained in this work provided new insights on the responses of plants to Fe deficiency, suggesting that this nutritional disorder differentially affected N metabolism in root and in leaf. Indeed under Fe deficiency, roots respond more efficiently, sustaining the whole plant by furnishing metabolites (i.e. aa, organic acids) to the leaves.
Dipartimento di Scienze Agrarie e Ambientali - Produzione, Territorio, Agroenergia, Università degli Studi di Milano, Milano, Italy.
Andrea
A
Borlotti
Gianpiero
G
Vigani
Graziano
G
Zocchi
D000410:Alanine Transaminase / Q000378:metabolism; D000596:Amino Acids / Q000378:metabolism; D001219:Aspartate Aminotransferases / Q000378:metabolism; D015153:Blotting, Western; D002734:Chlorophyll / Q000378:metabolism; D002951:Citrates / Q000378:metabolism; D018553:Cucumis sativus / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D050790:Glutamate Synthase (NADH) / Q000378:metabolism; D007501:Iron / Q000494:pharmacology; D000090463:Iron Deficiencies; D007521:Isocitrate Dehydrogenase / Q000378:metabolism; D008954:Models, Biological; D050901:Nitrate Reductase / Q000235:genetics / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D010788:Photosynthesis / Q000187:drug effects; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism; D018526:Plant Transpiration / Q000187:drug effects
D000596:Amino Acids; D002951:Citrates; D009566:Nitrates; D002734:Chlorophyll; D007501:Iron; D007521:Isocitrate Dehydrogenase; D050790:Glutamate Synthase (NADH); D050901:Nitrate Reductase; D001219:Aspartate Aminotransferases; D000410:Alanine Transaminase; D009584:Nitrogen