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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) Enzymatic activity and (B) Northern Blot analysis of GS and GOGAT. 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 meaning of the columns and the measurement units of enzymatic activities is as reported in Figure2. Control (0 d) activity of GS was 259 and 520 nmol NADH mg-1 prot min-1, respectively for root and leaf. GS1, root isoform; GS2, leaf isoform. Control activity of GOGAT was 140 and 112 nmol NADH mg-1 prot min-1, respectively for root and leaf. Fd-GOGAT, ferredoxin-dependent isoform; NADH-GOGAT, NADH-dependent isoform (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 4: (A) Enzymatic activity and (B) Northern Blot analysis of GS and GOGAT. 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 meaning of the columns and the measurement units of enzymatic activities is as reported in Figure2. Control (0 d) activity of GS was 259 and 520 nmol NADH mg-1 prot min-1, respectively for root and leaf. GS1, root isoform; GS2, leaf isoform. Control activity of GOGAT was 140 and 112 nmol NADH mg-1 prot min-1, respectively for root and leaf. Fd-GOGAT, ferredoxin-dependent isoform; NADH-GOGAT, NADH-dependent isoform (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: As soon as NO3- is reduced by NR and NiR, the NH4+ follows the N assimilation pathway through the GS/GOGAT cycle. Figure4A and Additional file1 (upper panels) shows the effect of Fe deficiency on the GS activity. This activity in root increased under Fe deficiency by about 30% in all days assayed, while it did not show any significant differences at the leaf level. Gene expression analysis of GS was performed on both the cytosolic (GS1) and plastidial (GS2) isoforms. As shown in Figure4B (upper panels), GS1 was more expressed in the roots while GS2 was preferentially expressed in the leaves. In agreement with the increased enzymatic activity, the GS1 transcript was over expressed under Fe deficiency at the root level (particularly after 3 d), and in leaves at d 1, 3 and 7 (Figure4B). The GS2 transcript was barely detected in roots while in leaves showed a decrease with the time (Figure4B).


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

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

(A) Enzymatic activity and (B) Northern Blot analysis of GS and GOGAT. 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 meaning of the columns and the measurement units of enzymatic activities is as reported in Figure2. Control (0 d) activity of GS was 259 and 520 nmol NADH mg-1 prot min-1, respectively for root and leaf. GS1, root isoform; GS2, leaf isoform. Control activity of GOGAT was 140 and 112 nmol NADH mg-1 prot min-1, respectively for root and leaf. Fd-GOGAT, ferredoxin-dependent isoform; NADH-GOGAT, NADH-dependent isoform (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 4: (A) Enzymatic activity and (B) Northern Blot analysis of GS and GOGAT. 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 meaning of the columns and the measurement units of enzymatic activities is as reported in Figure2. Control (0 d) activity of GS was 259 and 520 nmol NADH mg-1 prot min-1, respectively for root and leaf. GS1, root isoform; GS2, leaf isoform. Control activity of GOGAT was 140 and 112 nmol NADH mg-1 prot min-1, respectively for root and leaf. Fd-GOGAT, ferredoxin-dependent isoform; NADH-GOGAT, NADH-dependent isoform (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: As soon as NO3- is reduced by NR and NiR, the NH4+ follows the N assimilation pathway through the GS/GOGAT cycle. Figure4A and Additional file1 (upper panels) shows the effect of Fe deficiency on the GS activity. This activity in root increased under Fe deficiency by about 30% in all days assayed, while it did not show any significant differences at the leaf level. Gene expression analysis of GS was performed on both the cytosolic (GS1) and plastidial (GS2) isoforms. As shown in Figure4B (upper panels), GS1 was more expressed in the roots while GS2 was preferentially expressed in the leaves. In agreement with the increased enzymatic activity, the GS1 transcript was over expressed under Fe deficiency at the root level (particularly after 3 d), and in leaves at d 1, 3 and 7 (Figure4B). The GS2 transcript was barely detected in roots while in leaves showed a decrease with the time (Figure4B).

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