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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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Nitrate, citrate and total aa concentration in the xylem sap and plant transpiration rate (E). Xylem sap was collected from plant during the progression of Fe deficiency treatment. Sampling was performed at 0, 1, 3, 7 days after Fe withdraw. The concentration is expressed as μM. Data are means ± SE (n = 3). In the case of significant difference (P<0.05) values with different letters are statistically different.
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Figure 6: Nitrate, citrate and total aa concentration in the xylem sap and plant transpiration rate (E). Xylem sap was collected from plant during the progression of Fe deficiency treatment. Sampling was performed at 0, 1, 3, 7 days after Fe withdraw. The concentration is expressed as μM. Data are means ± SE (n = 3). In the case of significant difference (P<0.05) values with different letters are statistically different.

Mentions: Table1 reports for all the aa determined the differences between 0 d and 7 d. In particular, Asp showed a decrease in Fe-deficient roots (−49%) while it increased in Fe-deficient leaves (+125%). The Asn concentration differed at leaf level where the increase was about 13-fold at 7 d of -Fe condition compared to the control, while it did not show any difference in the roots (Figure5). The change of Glu and Gln was very similar, but, in Fe-deficient tissues, Gln decreased more in root (−64%) and increased more in leaf (3-fold) when compared with Glu (−52% and +138%, in roots and leaves, respectively). Similarly, the concentration of Ser and Gly decreased in root while it increased in leaf, as Fe deficiency condition proceed. However, the Ser decrease in root was only significant at d 3 (−38%), while Gly decreased in root by about 25% after 7 d of Fe deficiency. At the same time both Ser and Gly increased in leaves (+94% and +160%, respectively). Interestingly, only the Arg showed a significant decreased concentration at d 7 in both roots (−96%) and leaves (−35%). The different aa concentration between roots and leaves prompted us to measure their translocation through the xylem. As shown in Figure6 the concentration of total aa in xylem sap was increased in Fe-deficient roots and after 7d of Fe deficiency it reached the maximum level (+50%). At the same time also the citrate concentration was increased in the xylem sap at d 7 (+50%), confirming the data obtained by Abadía and co-workers[41]. On the contrary, at d 7 the concentration of NO3- in the xylem was slightly decreased (−14%). The data collected from xylem sap are considered as an amount increase in nitrate, citrate and aa, since transpiration (E) rate did not change during the expression of Fe deficiency (Figure6).


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

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

Nitrate, citrate and total aa concentration in the xylem sap and plant transpiration rate (E). Xylem sap was collected from plant during the progression of Fe deficiency treatment. Sampling was performed at 0, 1, 3, 7 days after Fe withdraw. The concentration is expressed as μM. Data are means ± SE (n = 3). 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 6: Nitrate, citrate and total aa concentration in the xylem sap and plant transpiration rate (E). Xylem sap was collected from plant during the progression of Fe deficiency treatment. Sampling was performed at 0, 1, 3, 7 days after Fe withdraw. The concentration is expressed as μM. Data are means ± SE (n = 3). In the case of significant difference (P<0.05) values with different letters are statistically different.
Mentions: Table1 reports for all the aa determined the differences between 0 d and 7 d. In particular, Asp showed a decrease in Fe-deficient roots (−49%) while it increased in Fe-deficient leaves (+125%). The Asn concentration differed at leaf level where the increase was about 13-fold at 7 d of -Fe condition compared to the control, while it did not show any difference in the roots (Figure5). The change of Glu and Gln was very similar, but, in Fe-deficient tissues, Gln decreased more in root (−64%) and increased more in leaf (3-fold) when compared with Glu (−52% and +138%, in roots and leaves, respectively). Similarly, the concentration of Ser and Gly decreased in root while it increased in leaf, as Fe deficiency condition proceed. However, the Ser decrease in root was only significant at d 3 (−38%), while Gly decreased in root by about 25% after 7 d of Fe deficiency. At the same time both Ser and Gly increased in leaves (+94% and +160%, respectively). Interestingly, only the Arg showed a significant decreased concentration at d 7 in both roots (−96%) and leaves (−35%). The different aa concentration between roots and leaves prompted us to measure their translocation through the xylem. As shown in Figure6 the concentration of total aa in xylem sap was increased in Fe-deficient roots and after 7d of Fe deficiency it reached the maximum level (+50%). At the same time also the citrate concentration was increased in the xylem sap at d 7 (+50%), confirming the data obtained by Abadía and co-workers[41]. On the contrary, at d 7 the concentration of NO3- in the xylem was slightly decreased (−14%). The data collected from xylem sap are considered as an amount increase in nitrate, citrate and aa, since transpiration (E) rate did not change during the expression of Fe deficiency (Figure6).

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