Responses of Arabidopsis thaliana to bicarbonate-induced iron deficiency

Morpho-physiological and biochemical responses of Arabidopsis thaliana (accession N1438) to bicarbonate-induced iron deficiency were investigated. Plants were grown in cabinet under controlled conditions, in a nutrient solution containing 5 μM Fe, added or not with 10 mM NaHCO₃. After 30 days, bicarbonate-treated plants displayed significantly lower biomass, leaf number and leaf surface area as compared to control plants, and slight yellowing of their younger leaves was observed. Potassium (K⁺) content was not modified by bicarbonate treatment in roots, whereas it was significantly diminished in shoots. Their content in ferrous iron (Fe²⁺) and in leaf total chlorophylls was noticeably lower than in control plants. Root Fe(III)-chelate reductase and phosphoenolpyruvate carboxylase (PEPC) activities were significantly enhanced, but leaf ribulose 1.5-bisphosphate carboxylase (Rubisco) activity was decreased.     

Genotypic variability within Tunisian grapevine varieties (Vitis vinifera L.) facing bicarbonate-induced iron deficiency

Morpho-physiological responses to bicarbonate-induced Fe deficiency were investigated in five Vitis vinifera L. Tunisian varieties (Khamri, Blanc3, Arich Dressé, Beldi, and Balta4). One-month-old woody cuttings were cultivated for 85 days on a free calcareous soil irrigated with tap water containing increasing bicarbonate levels (0, 4, 8, 12, and 16 mM NaHCO₃). After this screening, a second experiment compared root biochemical responses of two contrasting genotypes (tolerant-sensitive) dealing with bicarbonate-induced iron deprivation (20 μM Fe ± 10 mM HCO₃⁻) for 75 days. Using morpho-physiological criteria, grapevine tolerance to HCO₃⁻-induced Fe shortage appeared to be genotype-dependent: Balta4 and Beldi varieties showed the highest leaf-chlorosis score (especially at the extreme HCO₃⁻ levels), in contrast to Khamri variety. Growth parameters (shoot height, total leaf area, leaf number, and biomass production) as well as juvenile leaf chlorophyll content were also differently affected depending on both genotype and bicarbonate dose. At 16 mM HCO₃⁻, Khamri was the less sensitive variety, contrasting with Balta4. On the other hand, chlorophyll content correlated positively with HCl-extractible Fe content of the juvenile leaves, suggesting that the grapevine response to iron deficiency may partly depend on to the plant ability to adequately supply young leaves with this element. Root biochemical responses revealed a relatively higher root acidification capacity in Khamri (tolerant) under Fe-deficiency while no significant changes occurred in Balta4 (sensitive). In addition, Fe(III)-reductase and phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31) activities were strongly stimulated by Fe-deficiency in Khamri, while remaining constant in Balta4. These findings suggest that biochemical parameters may constitute reliable criteria for the selection of tolerant grapevine genotypes to iron chlorosis.     

Use of in vitro method to evaluate some grapevine varieties for tolerance and susceptibility to sodium bicarbonate-induced chlorosis

Nodal shoot segments of four grapevine genotypes well known for their Fe-chlorosis characteristic [Vitis vinifera × Vitis berlandieri Fercal, resistant; V. berlandieri × Vitis rupestris 1103 P, mid-resistant; Solonis (Vitis riparia × V. rupestris × Vitis candicans) × Othello (Vitis labrusca × V. riparia × V. vinifera) 1613 C, susceptible; V. vinifera L. cv. Perlette, resistant] were cultured in vitro. The effects of three levels of iron sodium ethylene-diaminotetraacetate (FeNaEDTA; 9, 18, 36 mg l⁻¹) and three mixtures of iron and 840 mg l⁻¹ NaHCO₃ (sodium bicarbonate) in the Murashige and Skoog (MS) medium supplemented 4.9 μM indole-3-butyric acid (IBA) were compared. We assayed the chlorosis rating of leaves, total chlorophyll of leaves, dry shoot weights of the plantlets, and active and total Fe content of the leaves. The most suitable concentration in determining the reaction of genotypes to iron chlorosis was 9 mg l⁻¹ FeNaEDTA. Bicarbonate addition had negative effects on the iron intake and development of plants. While all genotypes were affected by non-ferrous conditions, Fercal and Perlette were found to be the most resistant genotypes and 1613 C rootstock as the most susceptible. The chlorosis rating of the tested genotypes ranked according to their known degree of tolerance and susceptibility to lime-induced chlorosis. The results of this study showed that the in vitro technique could successfully be used in viticulture to get results in shorter times in the studies, aiming at breeding new rootstocks and varieties suitable to calcareous soil conditions and determining the reactions of existing genotypes to Fe chlorosis.     

Physiological responses and differential gene expression in Prunus rootstocks under iron deficiency conditions

Two Prunus rootstocks, the Myrobalan plum P 2175 and the interspecific peach-almond hybrid, Felinem, were studied to characterize their biochemical and molecular responses induced under iron-Deficient conditions. Plants of both genotypes were submitted to different treatments using a hydroponic system that permitted removal of Fe from the nutrient solution. Control plants were grown in 90 μM Fe (III)-EDTA, Deficient plants were grown in an iron free solution, and plants submitted to an Inductor treatment were resupplied with 180 μM Fe (III)-EDTA over 1 and 2 days after a period of 4 or 15 days of growth on an iron-free solution. Felinem increased the activity of the iron chelate reductase (FC-R) in the Inductor treatment after 4 days of iron deprivation. In contrast, P 2175 did not show any response after at least 15 days without iron. The induction of the FC-R activity in this genotype was coincident in time with the medium acidification. These results suggest two different mechanisms of iron chlorosis tolerance in both Strategy I genotypes. Felinem would use the iron reduction as the main mechanism to capture the iron from the soil, and in P 2175, the mechanism of response would be slower and start with the acidification of the medium synchronized with the gradual loss of chlorophyll in leaves. To better understand the control of these responses at the molecular level, the differential expression of PFRO2, PIRT1 and PAHA2 genes involved in the reductase activity, the iron transport in roots, and the proton release, respectively, were analyzed. The expression of these genes, estimated by quantitative real-time PCR, was different between genotypes and among treatments. The results were in agreement with the physiological responses observed.     

Effect of iron chlorosis-inducing factors on the pH of the cytoplasm of sunflower (Helianthus annuus)

Summary Growth chamber experiments with sunflower in nutrient solution were performed to investigate the effect of phosphorus and bicarbonate in inducing iron chlorosis.Iron chlorosis as proved by lower dry matter yield and reduced chlorophyll content was induced by bicarbonate alone and more pronounced by a combination of bicarbonate and phosphate, but not by phosphate alone.Iron content of roots and aerial plant parts was reduced by bicarbonate in all experiments, but only in one experiment by phosphate alone.Bicarbonate in the nutrient medium increased the pH of the cytoplasm in leaf cells, while phosphate had no effect.A daily adjustment of the pH in the nutrient medium to a value comparable to that in the bicarbonate trial, did not affect the pH of the cytoplasm.It is concluded that the pH of the cytoplasm plays an important role in establishing plant resistance or susceptibility to Fe chlorosis.     

Physiological and biochemical adjustment of iron chlorosis affected low-chill peach cultivars supplied with different iron sources

A pot experiment was carried out to investigate the effect of iron supplementation on physiological and biochemical status of the low-chill peach cultivars (Saharanpur Prabhat, Shan-e-Punjab and Pratap) suffered from iron chlorosis in artificially created calcareous soil. Three most commonly used iron sources viz. Fe-sulphate (1.0 % and 0.5 %), Fe-citrate (1.0 % and 0.5 %) and FeEDTA (0.1 % and 0.2 %) were sprayed on the 4th and 5th leaves from the apex of the twig. And after 1 week of spraying, observation on various physiological and biochemical parameters in leaves were recorded. Improvement in plant physiological parameters like chlorophyll content index (CCI), photosynthetic rate (P_n), stomatal conductance (g_s) and intercellular CO₂ conc. (C_i) were recorded best with the application of 1.0 % Fe-sulphate both in treated and untreated upper leaves. The maximum recovery in biochemical parameters such as total leaf chlorophyll content, superoxide dismutase (SOD) and peroxidase (POD) activity was also noted with the application of 1.0 % Fe-sulphate. However, application of 1.0 % Fe-sulphate and 0.5 % Fe-sulphate had similar effect for most of the parameters under study. The ability of iron sources to induce physiological and biochemical responses in iron deficient low-chill peach plants were in the following order Fe-sulphate>Fe-citrate>FeEDTA. Differential responses in plant physiological and biochemical parameters were also exhibited by the low-chill peach cultivars with regard to supplementation of various iron sources. Among the low-chill peach cultivars, Saharanpur Prabhat responded best with the application of iron sources followed by Shan-e-Punjab and Pratap.     

Physiological and biochemical responses of the iron chlorosis tolerant grapevine rootstock 140 Ruggeri to iron deficiency and bicarbonate

Background and aims

Iron (Fe) deficiency chlorosis associated with high levels of soil bicarbonate is one of the main nutritional disorders observed in sensitive grapevine genotypes. The aim of the experiment was to assess both the independent and combined effects of Fe and bicarbonate nutrition in grapevine.

Methods

Plants of the Fe chlorosis tolerant 140 Ruggeri rootstock were grown with and without Fe(III)-EDTA and bicarbonate in the nutrient solution. SPAD index, plant growth, root enzyme (PEPC, MDH, CS, NADP⁺ ?IDH) activities, kinetic properties of root PEPC, organic acid concentrations in roots and xylem sap and xylem sap pH were determined. A factorial statistical design with two factors (Fe and BIC) and two levels of each factor was adopted: +Fe and ?Fe, and +BIC and ?BIC.

Results

This rootstock strongly reacted to Fe deficiency by activating several response mechanisms at different physiological levels. The presence of bicarbonate in the nutrient solution changed the activity of PEPC and TCA related enzymes (CS, NADP⁺-IDH) and the accumulation/translocation of organic acids in roots of Fe-deprived plants. Moreover, this genotype increased root biomass and root malic acid concentration in response to high bicarbonate levels in the substrate. Bicarbonate also enhanced leaf chlorophyll content.

Conclusions

Along with a clear independent effect on Fe nutrition, our data support a modulating role of bicarbonate on Fe deficiency response mechanisms at root level.     

Proteomic analysis of Tunisian grapevine cultivar Razegui under salt stress

Salt stress is one of the major abiotic stresses in agriculture worldwide, especially in the Mediterranean area. We report here a proteomic approach to investigate the salt stress-responsive proteins in grapevine (Vitis vinifera). Two-dimensional electrophoresis (2-DE) was used to analyze the proteome of the salt-tolerant Tunisian grapevine cultivar Razegui, subjected to a supply of 100mm NaCl over 15d. Analysis of 2-DE gels derived from stressed plants revealed more than 800 reproducibly detected protein spots, with 48 proteins displaying a differential expression pattern, including 32 up-regulated, 9 down-regulated and 7 new protein spots induced after salt treatment. The presence of stress-responsive proteins in the different plant organs suggests that salt spreads systemically. Edman degradation analysis and database searching aided us in identifying a major protein GP. Database analysis revealed that this peptide has a 98% sequence similarity with a pathogenesis-related (PR) protein 10 (V. vinifera). A full-length cDNA encoding the GP protein was isolated from grapevine salt-stressed leaves and sequenced. The predicted protein contained 158 amino acids and showed 98% identity with PR10 protein of of V. vinifera (accession no. Cac16165).     

Responses of two ecotypes of <Emphasis Type="Italic">Medicago ciliaris</Emphasis> to direct and bicarbonate-induced iron deficiency conditions

Our study investigates the effect of iron deficiency on morpho-physiological and biochemical parameters of two Medicago ciliaris ecotypes (Mateur TN11.11 and Soliman TN8.7). Iron deficiency was imposed by making plants grow, either in an iron free or by the addition of CaCO₃/NaHCO₃ to the Hoagland nutrient solution. Our results showed that both true and bicarbonate Fe-deficiency induced the characteristic iron-chlorosis symptoms, although the intensity of the symptoms was ecotype-dependent. This variability in tolerance to iron deficiency was also displayed by other morphological parameters such as root biomass and chlorophyll concentration. Besides, iron chlorosis induced an increase in biochemical parameters: the iron reducing capacity (measured in vivo on root segments and in vitro on plasma membrane enriched vesicles) and rhizosphere acidification by enhancement of H⁺-ATPase activity were more pronounced in Mateur ecotype. These findings suggest that Soliman ecotype was more sensitive than Mateur one to iron chlorosis.     

Nitrogen nutrition influences some biochemical responses to iron deficiency in tolerant and sensitive genotypes of Vitis

The effects of nitrogen source on iron deficiency responses were investigated in two Vitis genotypes, one tolerant to limestone chlorosis Cabernet Sauvignon (Vitis vinifera cv.) and the other susceptible Gloire de Montpellier (Vitis riparia cv.). Plants were grown with or without Fe(III)-EDTA, and with NO₃⁻ alone or a mixture of NO₃⁻ and NH₄⁺. Changes in pH of the nutrient solution and root ferric chelate reductase (FC-R) activity were monitored over one week. We carried out quantitative metabolic profiling (¹H-NMR) and determined the activity of enzymes involved in organic acid metabolism in root tips. In iron free-solutions, with NO₃⁻ as the sole nitrogen source, the typical Fe-deficiency response reactions as acidification of the growth medium and enhanced FC-R activity in the roots were observed only in the tolerant genotype. Under the same nutritional conditions, organic acid accumulation (mainly citrate and malate) was found for both genotypes. In the presence of NH4⁺, the sensitive genotype displayed some decrease in pH of the growth medium and an increase in FC-R activity. For both genotypes, the presence of NH₄⁺ ions decreased significantly the organic acid content of roots. Both Vitis genotypes were able to take up NH₄⁺ from the nutrient solution, regardless of their sensitivity to iron deficiency. The presence of N-NH₄⁺ modified typical Fe stress responses in tolerant and sensitive Vitis genotypes.     

Genotypical differences in responses to iron deficiency between sensitive and resistant cultivars of chickpea (Cicer arietinum)

Differences in responses to iron deficiency between two chickpea cultivars, NP-62 and K-850, were examined. The apical leaves of NP-62 quickly showed symptoms of iron-deficiency chlorosis when grown on an iron-free medium. By contrast, K-850 showed no visible symptoms on the same medium. Iron contents of the apical leaves of these two cultivars were similar during the first 7 days after they were transferred to the iron-free medium in spite of a marked difference in root-associated Fe³⁺-reduction activity. The susceptibility to iron-deficiency chlorosis observed in NP-62 was not attributable to the poor Fe³⁺-reduction activity of roots but to the inefficient utilization of iron within leaves under conditions when the supply of iron was limited.     

Differences in responses to iron deficiency among various cultivars of mungbean (Vigna radiata (L.) Wilczek)

Ten mungbean cultivars were evaluated for their resistance to iron deficiency in view of chlorosis symptoms, plant growth and seed yield under field conditions on a calcareous soil in Thailand. The KPS2 cultivar was highly susceptible; the KPS1, PSU1 and Pag-asa 1 cultivars were somewhat susceptible; the VC1163B cultivar was moderately tolerant; the CN36, CN60, UT1 and CNM-I cultivars were tolerant; and the CNM8509B cultivar was very tolerant to iron deficiency. Foliar application of a solution of 5 g L^-1 ferrous sulphate was effective in correcting chlorosis that was induced by iron deficiency, and it enhanced both the growth and the yield of susceptible cultivars. Compared with the susceptible cultivar KPS2, the tolerant cultivar UT1 had a greater ability to lower the pH of the nutrient solution in response to iron deficiency. The root-associated Fe³⁺-reduction activity of UT1 that had been grown in -Fe medium was similar to that of the plants grown in +Fe medium when the acidification of the medium occurred. Acidification of the medium in response to iron deficiency might contribute to the efficient solubilization of iron from calcareous soils, and it related more closely to the resistance to iron deficiency than Fe³⁺ reduction by roots in mungbean cultivars.     

A new technique of plant analysis to resolve iron chlorosis

Summary Iron though indispensable for the biosynthesis of chlorophyll, its total content in the plant was not associated with the occurrence of chlorosis. In order to overcome this inconsistency a new technique of plant iron analysis has been developed. It consists of the determination of Fe²⁺, the fraction of iron involved in the synthesis of chlorophyll.The choice of 1–10 o-phenanthroline (o-Ph) as an extractant for Fe²⁺ was based on its remarkably higher stability constant for Fe²⁺ than Fe³⁺. On this basis, it could preferentially chelate Fe²⁺. The highly specific organce colour of the Fe²⁺-phenanthroline complex made possible the determination of Fe²⁺ by reading the transmittancy at 510 nm.The procedure involves extraction of 2 g of thoroughly washed, chopped, fresh plant by 20 ml of o-phenanthroline extractant (pH 3.0, conc. 1.5%). The plant samples treated with the extractant are allowed to stand for 16 hours and Fe²⁺ is determined in the filtrate by reading the transmittancy at 510 nm.In sharp contrast to total iron the green plants always contained more Fe²⁺ than chlorotic plants. The technique has been developed for rice but is expected to be successful for other crops also.     

Oriented responses of grapevine moth larvae Lobesia botrana to volatiles from host plants and an artificial diet on a locomotion compensator

Larvae of the grapevine moth Lobesia botrana (Lepidoptera: Tortricidae) are a major pest of vine, Vitis vinifera. As larvae have limited energy reserves and are in danger of desiccation and predation an efficient response to plant volatiles that would guide them to food and shelter could be expected. The responses of starved 2nd or 3rd instar larvae to volatile emissions from their artificial diet and to single host plant volatiles were recorded on a locomotion compensator. Test products were added to an air stream passing over the 30 cm diameter servosphere. The larvae showed non-directed walks of low rectitude in the air stream alone but changed to goal-oriented upwind displacement characterised by relatively straight tracks when the odour of the artificial diet and vapours of methyl salicylate, 1-hexanol, (Z)-3-hexen-1-ol, terpinen-4-ol, 1-octen-3-ol, (E)-4,8-dimethyl-1,3,7-nonatriene and (Z)-3-hexenyl acetate were added to the air stream. This chemoanemotactic targeted displacement illustrates appetence for certain volatile cues from food by starved Lobesia larvae. Analysis of the larval behaviour indicates dose dependent responses to some of the host plant volatiles tested with a response to methyl salicylate already visible at 1 ng, the lowest source dose tested. These behavioural responses show that Lobesia larvae can efficiently locate mixtures of volatile products released by food sources as well as single volatile constituents of their host plants. Such goal-oriented responses with shorter travel time and reduced energy loss are probably of importance for larval survival as it decreases the time they are exposed to biotic and abiotic hazards.     

Role of iron metabolism in heart failure: From iron deficiency to iron overload

Iron metabolism is a balancing act, and biological systems have evolved exquisite regulatory mechanisms to maintain iron homeostasis. Iron metabolism disorders are widespread health problems on a global scale and range from iron deficiency to iron-overload. Both types of iron disorders are linked to heart failure. Iron play a fundamental role in mitochondrial function and various enzyme functions and iron deficiency has a particular negative impact on mitochondria function. Given the high-energy demand of the heart, iron deficiency has a particularly negative impact on heart function and exacerbates heart failure. Iron-overload can result from excessive gut absorption of iron or frequent use of blood transfusions and is typically seen in patients with congenital anemias, sickle cell anemia and beta-thalassemia major, or in patients with primary hemochromatosis. This review provides an overview of normal iron metabolism, mechanisms underlying development of iron disorders in relation to heart failure, including iron-overload cardiomyopathy, and clinical perspective on the treatment options for iron metabolism disorders.     

Plasma selenium status in children with iron deficiency anemia

Iron and selenium are trace elements necessary for the maintenance of life and health. Iron deficiency is the most common nutritional deficiency among children in the world. The purpose of this study was to evaluate plasma selenium concentrations in children with iron deficiency anemia (IDA). Plasma selenium levels were investigated in 56 children with IDA and in 48 control subjects aged 1-8 years. A spectrofluorometric method was used for the determination. Plasma selenium concentrations in children with IDA (33.6+/-8.2 microg/l) were significantly lower than in the control group (56.0+/-17.0 microg/l) (p<0.001). However, there was no relation between plasma selenium, iron and hemoglobin concentrations.     

Genetics of tolerance to iron chlorosis in rice

Genetics of tolerance to iron chlorosis was investigated in eight crosses involving parents distinctly different in their level of tolerance. The segregating populations with parents and F₁s were screened under actual stress conditions in the field. Also, selected crosses were studied for Fe³⁺ uptake capacity. Tolerance/moderate tolerance to Fe chlorosis was dominant over susceptibility and it was controlled by two sets of nonallelic genes with complementary interaction. Gene Ic ₁ has been found to be basic and in complementation with Ic ₃ it confers tolerance. Likewise, Ic ₂ with Ic ₄ confers tolerance. The basic genes Ic ₁ and Ic ₂ are nonallelic and, in the absence of their respective complementary genes Ic ₃ and ₄ , ineffective, which results in susceptibility. Of tolerant cultivars, ARC 10372 and Cauvery have been tentatively assigned the genotype of Ic ₁ , Ic ₂ , Ic ₃ , Ic ₄ , and moderately tolerant IET 7613, Prasanna and Akashi Ic ₁ , ₂ Ic ₃ Ic ₄ . The susceptible ARC 5723 has been assigned Ic ₁ , ₂ , Ic ₃ , Ic ₄ , and IET 9829, Ic ₁ , ₂ Ic ₃ Ic ₄ . IET 7614 is susceptible, due to the presence of inhibitory genes I-Ic ₁ , I-Ic ₂ together with ic ₁ pt>, ic ₂ , Ic ₃ , Ic ₄ . Further, the gene Pc for purple coleoptile shows linkage with one of the complementary genes with a crossover value of 15.26%, while the gene(s) for seedling height Ts with Ic ₁ with a crossover value of 1.7%. It is possible that the gene(s) for iron chlorosis tolerance might belong to the second linkage group, where genes for purple leaf were located.