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Iron deficiency affects nitrogen metabolism in cucumber (Cucumis sativus L.) plants.

Borlotti A, Vigani G, Zocchi G - BMC Plant Biol. (2012)

Bottom Line: 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Dipartimento di Scienze Agrarie e Ambientali - Produzione, Territorio, Agroenergia, Università degli Studi di Milano, Milano, Italy.

ABSTRACT

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.

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(A) Nitrate concentration, (B) enzymatic activity and (C) Northern Blot analyses of NR. Assay and northern blot were performed on root and leaf of plant during the progression of Fe deficiency treatment. Sampling was performed at 0, 1, 3, 7 days after Fe withdraw. The activities are expressed as percentage (%) of the relative activity of the Fe-deficient samples (columns 1, 3, 7 d) compared to Fe sufficient plants (column 0 d). Activity of control (0 d) was 5.6 and 9.8 nmol NADH mg-1 prot min-1, respectively for root and leaf (complete activity data are reported in Additional file1). Data are means ± SE (n = 4). In the case of significant difference (P<0.05) values with different letters are statistically different.
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Figure 2: (A) Nitrate concentration, (B) enzymatic activity and (C) Northern Blot analyses of NR. Assay and northern blot were performed on root and leaf of plant during the progression of Fe deficiency treatment. Sampling was performed at 0, 1, 3, 7 days after Fe withdraw. The activities are expressed as percentage (%) of the relative activity of the Fe-deficient samples (columns 1, 3, 7 d) compared to Fe sufficient plants (column 0 d). Activity of control (0 d) was 5.6 and 9.8 nmol NADH mg-1 prot min-1, respectively for root and leaf (complete activity data are reported in Additional file1). Data are means ± SE (n = 4). In the case of significant difference (P<0.05) values with different letters are statistically different.

Mentions: Figure2A shows the concentration of NO3- both in roots and in leaves. No significant differences among treatments were found for roots, while a decrease (−35%) was found in the leaves in all the days assayed after induction of Fe deficiency. The NR activity, which is the first enzyme in the NO3- assimilatory pathway, decreased both at root and at leaf level during the progression of the Fe deficiency-induced condition (1, 3, 7 d of -Fe). However, in Fe-deficient leaves, NR activity decrease was much more evident as compared to the root reaching −80% after 7 d, suggesting that Fe deficiency affected more the NR activity in the leaves than in the roots (Figure2B and Additional file1). On the contrary, under Fe deficiency, the NR transcript increased in roots, while in leaves its expression was strongly decreased, as revealed by northern blot analysis (Figure2C). These changes in the transcript levels were already evident 1 d after Fe removal.


Iron deficiency affects nitrogen metabolism in cucumber (Cucumis sativus L.) plants.

Borlotti A, Vigani G, Zocchi G - BMC Plant Biol. (2012)

(A) Nitrate concentration, (B) enzymatic activity and (C) Northern Blot analyses of NR. Assay and northern blot were performed on root and leaf of plant during the progression of Fe deficiency treatment. Sampling was performed at 0, 1, 3, 7 days after Fe withdraw. The activities are expressed as percentage (%) of the relative activity of the Fe-deficient samples (columns 1, 3, 7 d) compared to Fe sufficient plants (column 0 d). Activity of control (0 d) was 5.6 and 9.8 nmol NADH mg-1 prot min-1, respectively for root and leaf (complete activity data are reported in Additional file1). Data are means ± SE (n = 4). In the case of significant difference (P<0.05) values with different letters are statistically different.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3539955&req=5

Figure 2: (A) Nitrate concentration, (B) enzymatic activity and (C) Northern Blot analyses of NR. Assay and northern blot were performed on root and leaf of plant during the progression of Fe deficiency treatment. Sampling was performed at 0, 1, 3, 7 days after Fe withdraw. The activities are expressed as percentage (%) of the relative activity of the Fe-deficient samples (columns 1, 3, 7 d) compared to Fe sufficient plants (column 0 d). Activity of control (0 d) was 5.6 and 9.8 nmol NADH mg-1 prot min-1, respectively for root and leaf (complete activity data are reported in Additional file1). Data are means ± SE (n = 4). In the case of significant difference (P<0.05) values with different letters are statistically different.
Mentions: Figure2A shows the concentration of NO3- both in roots and in leaves. No significant differences among treatments were found for roots, while a decrease (−35%) was found in the leaves in all the days assayed after induction of Fe deficiency. The NR activity, which is the first enzyme in the NO3- assimilatory pathway, decreased both at root and at leaf level during the progression of the Fe deficiency-induced condition (1, 3, 7 d of -Fe). However, in Fe-deficient leaves, NR activity decrease was much more evident as compared to the root reaching −80% after 7 d, suggesting that Fe deficiency affected more the NR activity in the leaves than in the roots (Figure2B and Additional file1). On the contrary, under Fe deficiency, the NR transcript increased in roots, while in leaves its expression was strongly decreased, as revealed by northern blot analysis (Figure2C). These changes in the transcript levels were already evident 1 d after Fe removal.

Bottom Line: 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Dipartimento di Scienze Agrarie e Ambientali - Produzione, Territorio, Agroenergia, Università degli Studi di Milano, Milano, Italy.

ABSTRACT

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.

Show MeSH
Related in: MedlinePlus