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Transport of iron in plants: novel approaches to an old problem. Improved iron mobility and development of a new fertilizer based on grass-clipping extracts.

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Publications

The memory of iron stress in strawberry plants
Publication . Gama, Florinda; Saavedra, Teresa; Da Silva, José Paulo; Miguel, Maria; de Varennes, Amarilis; Correia, José Pedro; Pestana, Maribela
To provide information towards optimization of strategies to treat Fe deficiency, experiments were conducted to study the responses of Fe-deficient plants to the resupply of Fe. Strawberry (Fragaria x ananassa Duch.) was used as model plant. Bare-root transplants of strawberry (cv. 'Diamante') were grown for 42 days in Hoagland's nutrient solutions without Fe (Fe0) and containing 10 mu M of Fe as Fe-EDDHA (control, Fe10). For plants under Fe0 the total chlorophyll concentration of young leaves decreased progressively on time, showing the typical symptoms of iron chlorosis. After 35 days the Fe concentration was 6% of that observed for plants growing under Fe10. Half of plants growing under Fe0 were then Fe-resupplied by adding 10 mu M of Fe to the Fe0 nutrient solution (FeR). Full Chlorophyll recovery of young leaves took place within 12 days. Root ferric chelate-reductase activity (FCR) and succinic and citric acid concentrations increased in FeR plants. Fe partition revealed that FeR plants expressively accumulated this nutrient in the crown and flowers. This observation can be due to a passive deactivation mechanism of the FCR activity, associated with continuous synthesis of succinic and citric acids at root level, and consequent greater uptake of Fe. (C) 2016 Elsevier Masson SAS. All rights reserved.
Silencing of the FRO1 gene and its effects on iron partition in Nicotiana benthamiana
Publication . Gama, Florinda; Saavedra, Teresa; Dandlen, Susana; de Varennes, Amarilis; Correia, Pedro José; Pestana, Maribela; Nolasco, Gustavo
To evaluate the dynamic role of the ferric-chelate reductase enzyme (FCR) and to identify possible pathways of regulation of its activity in different plant organs an investigation was conducted by virus induced gene silencing (VIGS) using tobacco rattle virus (TRV) to silence the ferric reductase oxidase gene (FROI) that encodes the FCR enzyme. Half of Nicotiana benthamiana plants received the VIGS vector and the rest remained as control. Four treatments were imposed: two levels of Fe in the nutrient solution (0 or 2.5 mu M of Fe), each one with silenced or non-silenced (VIGS-0; VIGS-2.5) plants. Plants grown without iron (0; VIGS-0) developed typical symptoms of iron deficiency in the youngest leaves. To prove that FROI silencing had occurred, resupply of Fe (R) was done by adding 2.5 mu M of Fe to the nutrient solution in a subset of chlorotic plants (0-R; VIGS-R). Twelve days after resupply, 0-R plants had recovered from Fe deficiency while plants containing the VIGS vector (VIGS-R) remained chlorotic and both FRO1 gene expression and FCR activity were considerably reduced, consequently preventing Fe uptake. With the VIGS technique we were able to silence the FRO1 gene in N. benthamiana and point out its importance in chlorophyll synthesis and Fe partition. (C) 2017 Elsevier Masson SAS. All rights reserved.
A novel plant extract as a biostimulant to recover strawberry plants from iron chlorosis
Publication . Saavedra, Teresa; Gama, Florinda; Correia, P.J.; Da Silva, José Paulo; Miguel, Maria da Graça; de Varennes, Amarilis; Pestana, Maribela
The traditional agricultural production systems are evolving more towardorganic, sustainable or environmental friendly systems and products; how-ever, it is important to keep the yield and the quality of crops. The aim ofthis work was to evaluate the recovery of iron deficient strawberry plantsby foliar spray, using a gramineous plants extract (GE). Bare-root trans-plants of strawberry (Fragaria ananassaDuch. cv“Diamond”) were grownin a Hoagland’s nutrient solution with iron (Fe10) or without (Fe0). Forty-two days after Fe deprivation, plants grown without iron became chloroticand GE was applied. Three foliar applications were done, once per weekand the regreening was monitored using a SPAD apparatus. After twoapplications, a rapid but transient regreening was detected in youngleaves. Nevertheless, biomass and root/shoot ratio of recovered plants (GEtreatment) were similar to chlorotic plants (Fe0 treatment). Phosphorous,Mn and Fe contents were higher in crowns of GE plants at the end of theexperiment (67 days). The concentration of organic acids and ferric chela-te–reductase (FC-R) activity was also significantly higher in GE treatment. Itis possible that the high chelating capacity of the extract was responsible or the Fe internal transport and use.
Silencing of FRO1 gene affects iron homeostasis and nutrient balance in tomato plants
Publication . Gama, Florinda; Saavedra, Teresa; Dandlen, Susana; García‐Caparrós, Pedro; de Varennes, Amarilis; Nolasco, Gustavo; Correia, Pedro José; Pestana, Maribela
BackgroundIron chlorosis is an abiotic stress of worldwide importance affecting several agronomic crops. It is important to understand how plants maintain nutrient homeostasis under Fe deficiency and recovery. AimsWe used the virus-induced gene silencing (VIGS) method to elucidate the role of the FRO1 gene in tomato plants and identify the impact on regulation of the root ferric-chelate reductase (FCR) activity and nutritional homeostasis. MethodsTomato plantlets cv. "Cherry" were transferred into half-strength Hoagland's nutrient solution containing 0.5 & mu;M of Fe (Fe0.5). In phase I, two treatments were established: control (Fe0.5) plants and VIGS-0.5 plants corresponding to plants with the FRO1 gene silenced. In phase II, plants from Fe0.5 and VIGS-0.5 were transferred to new nutrient solution and then grown for a further 14 days under 0 and 10 & mu;M of Fe (as 0.5 & mu;M would not be enough for the larger plants during phase II). Therefore, four treatments were imposed: Fe0, Fe10, VIGS-0, and VIGS-10. ResultsVIGS-0.5 plants had significantly lower chlorophyll (Chl) and root FCR activity compared to the respective non-silenced plants and retained more Cu and Zn in the roots at the expense of stems (Cu) or young leaves (Zn). Iron concentration in roots and stems decreased in FRO1 gene-silenced plants, compared to control plants, but the allocation to different organs was similar in both treatments. ConclusionsThere was a partial recovery of leaf Chl in the VIGS-10 plants and a higher concentration of Fe in all organs. In contrast, the allocation of Cu to roots decreased in the VIGS-10 plants.
Nutritional performance of Five Citrus rootstocks under different Fe levels
Publication . Pestana, Maribela; García-Caparrós, Pedro; Saavedra, Teresa; Gama, Florinda; Abadía, Javier; Varennes, Amarilis de; Correia, Pedro José
Iron is an essential micronutrient for citrus, playing an important role in photosynthesis and yield. The aim of this paper was to evaluate the tolerance to Fe deficiency of five citrus rootstocks: sour orange (S), Carrizo citrange (C), Citrus macrophylla (M), Troyer citrange (T), and Volkamer lemon (V). Plants were grown for 5 weeks in nutrient solution that contained the following Fe concentrations (in µM): 0, 5, 10, 15, and 20. At the end of the experiment, biomass (dry weight— DW), leaf area, total leaf chlorophyll (CHL), and the activity of root chelate reductase (FCR) were recorded. Additionally, the mineral composition of roots (R) and shoots (S) was evaluated. Principal component analysis was used to study the relationships between all parameters and, subsequently, the relations between rootstocks. In the first component, N-S, P-S, Ca-S, Cu-S, Zn-S, Mn-S, Zn-R, and Mn-R concentrations were related to leaf CHL and FCR. Increases in leaf CHL, Mg-R, and DW (shoots and roots) were inversely related to Cu-R, which was shown in the second component. The values obtained were consistent for V10, C15, and C20, but in contrast for S0 and S5. In conclusion, micronutrient homeostasis in roots and shoots of all rootstocks were affected by Fe stress conditions. The Fe/Cu ratio was significantly related to CHL, which may be used to assist rootstock performance.

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Funding agency

Fundação para a Ciência e a Tecnologia

Funding programme

3599-PPCDT

Funding Award Number

PTDC/AGR-PRO/3861/2012

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