Cation transporters/channels in plants: Tools for nutrient biofortification

Cation transporters/channels are key players in a wide range of physiological functions in plants, including cell signaling, osmoregulation, plant nutrition and metal tolerance. The recent identification of genes encoding some of these transport systems has allowed new studies toward further understanding of their integrated roles in plant. This review summarizes recent discoveries regarding the function and regulation of the multiple systems involved in cation transport in plant cells. The role of membrane transport in the uptake, distribution and accumulation of cations in plant tissues, cell types and subcellular compartments is described. We also discuss how the knowledge of inter- and intra-species variation in cation uptake, transport and accumulation as well as the molecular mechanisms responsible for these processes can be used to increase nutrient phytoavailability and nutrients accumulation in the edible tissues of plants. The main trends for future research in the field of biofortification are proposed.

Selenate and selenite on yield and agronomic biofortification with selenium in rice

The objective of this work was to evaluate the effect of doses of selenate and selenite on rice (Oryza sativa) biofortification with Se, as well the influence of these forms of Se in the levels of P, S, Fe, and Zn in grains. The experiment was conducted in a greenhouse, in pots with 4 dm(3) of a sandy clay loam Latosol, with medium texture, in a 5x2 factorial arrangement with five doses of Se (0, 0.75, 1.50, 3.0, and 6.0 mg dm(-3)) and two forms of Se (selenate and selenite). Selenate provided greater efficiency of root uptake of Se, plant-use efficiency, translocation from roots to shoots, and content of this element in rice grains. The application of Se during fertilization influences the levels of P, S, and Zn, but does not affect those of Fe in rice grains.

Cultivares de feijoeiro: efeito do solo, adubação foliar e competição com trapoeraba

O feijoeiro (Phaseolus vulgaris L.) é um dos principais alimentos consumidos no Brasil, rico em vitaminas, carboidratos e minerais. É crescente o número de pesquisas que integram desde o melhoramento de plantas e o manejo da adubação para incrementar nutrientes nas partes comestíveis, desenvolvendo plantas com maiores teores de vitaminas e micronutrientes. A introdução de alimentos biofortificados como o feijão, complementa a nutrição humana que sofre com desnutrição. Sendo assim, é importante conhecer como as condições de cultivo influenciam na qualidade do grão e na importância para obtenção de um alimento com maior valor nutricional. Além de conhecer até que ponto a influência de planta daninha afeta a produção e a absorção de nutrientes pelo feijoeiro. O objetivo deste trabalho foi analisar as características agronômicas e nutricionais influenciadas pela interferência de planta daninha, efeito da adubação e do solo, nas cultivares de feijão. Foi avaliado o teor de clorofila, número de folhas, diâmetro do caule, número de vagem por planta, índice de colheita por planta, massa seca da trapoeraba, relação grão e lócus, peso médio de sementes e análise de ferro e zinco nas folhas e nos grãos. Os resultados obtidos no estudo apontaram que a competição com trapoeraba afetou algumas características agronômicas, devido à competição por nutriente. O solo para cultivo também interferiu na produção, o solo eutrófico proporcionou melhores resultados das cultivares. A adubação não interferiu nos teores de ferro e zinco nos grãos do feijoeiro. As cultivares BRS Agreste, BRS Ametista e BRS Estilo apresentaram melhores resultados na maioria das características analisadas. Por fim, conclui-se que a produção do feijoeiro, necessita de um solo com uma boa nutrição, um bom teor de matéria orgânica, manejo da adubação e de plantas daninhas para aumentar a produção.

Genetic control of iron concentration in Mesoamerican and Andean common bean seeds

The objective of this work was to evaluate the main differences in the genetic control of the iron concentration in Mesoamerican and Andean common bean seeds, in early generations, and to select recombinants with a high iron concentration in the seeds. F1, F1 reciprocal, F2, F2 reciprocal, and backcross (BC11 and BC12) generations were produced by crosses between Mesoamerican (CNFP 10104 x CHC 01-175) and Andean (Cal 96 x Hooter) inbred lines. The expression of significant maternal effect was observed for the Mesoamerican gene pool. Iron concentration was higher in the seed coat of Mesoamerican common bean seeds (54.61 to 67.92%) and in the embryo of Andean common bean seeds (69.40 to 73.44%). High broad-sense heritability was obtained for iron concentration in Mesoamerican and Andean common bean seeds. Gains with the selection of higher magnitude, from 20.39 to 24.58%, are expected in Mesoamerican common bean seeds. Iron concentration in common bean seeds showed a continuous distribution in F2, which is characteristic of quantitative inheritance in Mesoamerican and Andean common bean seeds. Recombinants with high iron concentration in seeds can be selected in both Mesoamerican and Andean common bean hybrids.

Iron and zinc availability in maize lines

The aim of this study was to characterize the Zn and Fe availability by phytic acid/Zn and phytic acid/Fe molar ratios, in 22 tropical maize inbred lines with different genetic backgrounds. The Zn and Fe levels were determined by atomic absorption spectrophotometry and the P through colorimetry method. Three screening methods for phytic acid (Phy) analysis were tested and one, based on the 2,2'-bipyridine reaction, was select. There was significant variability in the contents of zinc (17.5 to 42 mg.kg-1), iron (12.2 to 36.7 mg.kg-1), phosphorus (230 to 400 mg.100 g-1), phytic acid (484 to 1056 mg.100 g-1), phytic acid P (140 to 293 mg.100 g-1) and available-P (43.5 to 199.5 mg.100 g-1), and in the available-P/total-P ratio (0.14 to 0.50), Phy/Zn (18.0 to 43.5) and Phy/Fe (16.3 to 45.5) molar ratios. Lines 560977, 560978 and 560982 had greater availability of Zn and lines 560975, 560977, 561010 and 5610111 showed better Fe availability. Lines 560975, 560977 and 560978 also showed better available-P/total-P ratio. Thus, the lines 560975, 560977 and 560978 were considered to have the potential for the development of cultivars of maize with high availability of Fe and/or Zn.

Nutritional characteristics of biofortified common beans

Iron and zinc deficiency can cause anemia and alterations in the immune response and impair work capacity. To minimize this problem, biofortification has been developed to improve and/or maintain the nutritional status of the population. Beans are an important source of carbohydrates, proteins, and minerals. The objective of this study is to characterize biofortified beans, quantify the minerals in different cultivars, and determine mineral dialysis. Grains of raw and cooked beans were analyzed for moisture, protein, lipids, fiber, minerals, and in vitro availability using four treatments and one control. The data were analyzed using ANOVA, and the Tukey test (p<0.05). The chemical composition of the raw and cooked treatments showed a moisture content ranging from 13.4 to 81.4%, protein from 22.24 to 31.59%, lipids from 1.66 to 2.22%, fiber from 16.81 to 40.63%, carbohydrates from 27.80 to 34.78%, and ash from 4.1 to 4.82%. Different varieties of beans showed statistically significant differences in iron and zinc content compared to the control cultivar (Pérola). The iron content differed significantly from that of the Pérola cultivar in the raw treatment, while in the cooked treatment, the control cultivar did not differ from the Piratã. The same behavior was observed for the zinc content in both treatments. There was no significant difference between the cultivars in the treatments in terms of the content of the dialysis of Calcium (Ca), Iron (Fe), Magnesium (Mg), and Zinc (Zn).

Influence of the moisture at harvest and drying process of the grains on the level of carotenoids in maize (Zea mays)

AbstractMaize is considered a source of carotenoids; however, these compounds are highly unstable, degraded by high temperatures, exposure to light and presence of oxygen. The objective of this work was to evaluate the influence of the moisture and type of drying applied to grains on the level of carotenoids in yellow maize. The experiment was conducted in a completely randomized design (2 × 4 factorial), two levels of initial moisture at the harvest (22 and 19%) and three types of drying (in the sun; in the shade and in a dryer) and control (no drying). The samples of grains after drying with 12% of final moisture were analyzed by concentration of total carotenoids, carotenes (α-carotene + β-carotene), monohydroxilated carotenoids (β-cryptoxanthin), and xanthophylls (lutein + zeaxanthin). Initial moisture, type of drying and the interaction between moisture versus drying influence (p≤0.05) the levels of carotenoids in grains. This is the first report about the drying conditions and harvest’s initial moisture as influence on the profile and content of carotenoids in maize grains. Based on the results, this work suggested that the harvest be carried out preferably when the grains present 22% humidity, with drying in a dryer or in shade for further use or storage.

Soil factors associated with zinc deficiency in crops and humans

Zinc deficiency is the most ubiquitous micronutrient deficiency problem in world crops. Zinc is essential for both plants and animals because it is a structural constituent and regulatory co-factor in enzymes and proteins involved in many biochemical pathways. Millions of hectares of cropland are affected by Zn deficiency and approximately one-third of the human population suffers from an inadequate intake of Zn. The main soil factors affecting the availability of Zn to plants are low total Zn contents, high pH, high calcite and organic matter contents and high concentrations of Na, Ca, Mg, bicarbonate and phosphate in the soil solution or in labile forms. Maize is the most susceptible cereal crop, but wheat grown on calcareous soils and lowland rice on flooded soils are also highly prone to Zn deficiency. Zinc fertilizers are used in the prevention of Zn deficiency and in the biofortification of cereal grains.

Zinc in plants

Zinc (Zn) is an essential component of thousands of proteins in plants, although it is toxic in excess. In this review, the dominant fluxes of Zn in the soil-root-shoot continuum are described, including Zn inputs to soils, the plant availability of soluble Zn(2+) at the root surface, and plant uptake and accumulation of Zn. Knowledge of these fluxes can inform agronomic and genetic strategies to address the widespread problem of Zn-limited crop growth. Substantial within-species genetic variation in Zn composition is being used to alleviate human dietary Zn deficiencies through biofortification. Intriguingly, a meta-analysis of data from an extensive literature survey indicates that a small proportion of the genetic variation in shoot Zn concentration can be attributed to evolutionary processes whose effects manifest above the family level. Remarkable insights into the evolutionary potential of plants to respond to elevated soil Zn have recently been made through detailed anatomical, physiological, chemical, genetic and molecular characterizations of the brassicaceous Zn hyperaccumulators Thlaspi caerulescens and Arabidopsis halleri.

Bio-fortification of potato tubers using foliar zinc-fertiliser

Worldwide, many people are zinc (Zn)-deficient. Dietary Zn intake can be increased by producing crops with higher concentrations of Zn in their edible portions. This can be achieved by applying Zn-fertilisers to varieties with an increased ability to acquire Zn and to accumulate Zn in their edible portions. Potato (Solanum tuberosum L.) is an important food crop and is, therefore, a target for bio-fortification with Zn. Field trials incorporating a core collection of 23 potato genotypes, performed over 4 years (2006 – 2009), indicated significant genotypic effects on tuber Zn concentration and suggested that tuber Zn concentration was influenced by environmental effects, but also found that genotype environment (G E) interactions were not significant. Tuber Zn concentrations averaged 10.8 mg kg–1 dry matter (DM), and the ratio between the lowest and the highest varietal tuber Zn-concentration averaged 1.76. Tuber Zn concentrations could be increased by foliar Zn-fertilisation. Tuber yields of ‘Maris Piper’ were unaffected by foliar applications of < 1.08 g Zn plant–1. The relationship between tuber Zn concentration and foliar Zn application followed a saturation curve, reaching a maximum at approx. 30 mg Zn kg–1 DM at a foliar Zn application rate of 1.08 g plant–1. Despite a 40-fold increase in shoot Zn concentration compared to the unfertilised controls following foliar Zn fertilisation with 2.16 g Zn plant–1, only a doubling in tuber Zn concentration was observed. This suggests that the biofortification of tubers with Zn was restricted by the limited mobility of Zn in the phloem. A significant positive linear relationship between tuber Zn concentration and tuber N concentration supported the hypothesis of co-transport of Zn and N-compounds in the phloem.

Genetical and comparative genomics of Brassica under altered Ca supply identifies Arabidopsis Ca-transporter orthologs

Although Ca transport in plants is highly complex, the overexpression of vacuolar Ca2+ transporters in crops is a promising new technology to improve dietary Ca supplies through biofortification. Here, we sought to identify novel targets for increasing plant Ca accumulation using genetical and comparative genomics. Expression quantitative trait locus (eQTL) mapping to 1895 cis- and 8015 trans-loci were identified in shoots of an inbred mapping population of Brassica rapa (IMB211 × R500); 23 cis- and 948 trans-eQTLs responded specifically to altered Ca supply. eQTLs were screened for functional significance using a large database of shoot Ca concentration phenotypes of Arabidopsis thaliana. From 31 Arabidopsis gene identifiers tagged to robust shoot Ca concentration phenotypes, 21 mapped to 27 B. rapa eQTLs, including orthologs of the Ca2+ transporters At-CAX1 and At-ACA8. Two of three independent missense mutants of BraA.cax1a, isolated previously by targeting induced local lesions in genomes, have allele-specific shoot Ca concentration phenotypes compared with their segregating wild types. BraA.CAX1a is a promising target for altering the Ca composition of Brassica, consistent with prior knowledge from Arabidopsis. We conclude that multiple-environment eQTL analysis of complex crop genomes combined with comparative genomics is a powerful technique for novel gene identification/prioritization.

Selenato e selenito na produção, nutrição mineral e biofortificação com selênio em cultivares de alface

SELENATE and SELENITE on YIELD, MINERAL NUTRITION and BIOFORTIFICATION WITH SELENIUM IN LETTUCE CULTIVARSSelenium is an important antioxidant element associated with physiological processes in plants, microorganisms, animals, and humans. However, its mode of action and essentiality in plants are still disputed. In Brazil, information on Se in agricultural crops is extremely scarce, though there are indications that low levels of Se are being consumed by the population. The objective of this study was to evaluate the effect of selenate and selenite on yield, mineral nutrition and biofortification with Se of lettuce cultivars. The experiment was arranged in a completely randomized factorial design 5 x 3 x 2, with five lettuce cultivars (Maravilha de Verao, Rafaela, Great Lakes, Veneranda, and Vera), three Se concentrations (0, 10 and 20 mu mol L(-1)) and two forms of Se (selenate and selenite), with four replicates. Results indicate that selenate application is more appropriate for biofortification of lettuce cultivars, while the effect of selenite proved to be more toxic. The application of selenate results in increased S shoot concentrations, while selenite reduced P concentrations, and both Se forms decreased micronutrient concentrations. No genotypic variation among lettuce cultivars was observed for Se concentration, and little variation was observed for shoot dry matter yield and S, Mg, Mn, and Fe levels.

Biofortificação com zinco, selênio e ferro, e biodisponibilidade de ferro em cultivares de feijoeiro-comum

The common bean (Phaseolus vulgaris L.), a staple food in nutritional diet of Brazilians and populations in developing countries, is a nutritionally rich legume with potential for biofortification. Approximately one third of the world population suffers from nutritional deficiencies, being necessary to increase the nutrient content in vegetables, especially iron (Fe), selenium (Se) and zinc (Zn), which are important micronutrients for plants and human health. In this context, three studies were carried out aiming to evaluate the potential of common bean cultivars to biofortification with Fe, Se and Zn, and verify the interaction between these minerals and iron bioavailability, in order to contribute to increased nutritional quality of grains, reducing the micronutrients deficiency and improving human health. In the first study, experiments were conducted in a greenhouse, with ten common bean cultivars in nutrient solution under different treatments with Fe, Se and Zn. The plant growth and the mineral content of the beans were evaluated in addition to verify the influence of polyphenol and phytate levels on Fe bioavailability in grains fortified with Zn and Se. The evaluated beans cultivars have proved promising for simultaneous biofortification with these nutrients without greatly affecting Fe bioavailability. In the second study, the aim was evaluate the interaction between Fe, Se and Zn in cultivars consumed in Brazil or in USA. Gene expression and root microscopy analysis were performed in order to understand the positive effect of Zn supply on the Fe uptake by roots. The expression of genes related to the transport and uptake of Fe and Zn did not clearly explain the influence of Zn in Fe nutrition. The roots microscopy and the evaluation of nutrient solutions used showed that, in the presence of Zn, there was Fe accumulation in epidermis of the roots and not in the vascular system, prone to be precipitated when it goes through the root membrane. In the latest study, a field experiment was conducted to evaluate the effect of Zn fertilization via soil and foliar, in the content and accumulation of Fe and Zn in grains and in the yield of common bean cultivars, in addition to verify the amount of these micronutrients supplied by biofortified beans. The fertilization with Zn did not affect the yield, but provided high levels of this nutrient in grains of the cultivars analyzed, representing 27% of the recommended daily intake of Zn. The higher Fe content in beans, obtained when there was no application of foliar Zn, supplies 56% of the daily requirement of Fe.

Stability of Carotenoids, Total Phenolics and In Vitro Antioxidant Capacity in the Thermal Processing of Orange-Fleshed Sweet Potato (Ipomoea batatas Lam.) Cultivars Grown in Brazil

Intervention strategies regarding the biofortification of orange-fleshed sweet potato, which is a rich source of carotenoids for combating vitamin A deficiency, are being developed in Brazil. This study was conducted to evaluate the concentrations of individual carotenoids, total phenolic compounds and antioxidant capacity in the roots of four biofortified sweet potato cultivars that were raw or processed by four common heat treatments. HPLC, Folin-Ciocalteu, DPPH and ABTS assays were used. All cultivars showed high levels of carotenoids in raw roots, predominantly all-trans-beta-carotene (79.1-128.5 mg.100 g(-1) DW), suggesting a high estimated vitamin A activity. The CNPH 1194 cultivar reported carotenoids values highest than those of other cultivars (p < 0.05). The total phenolic compounds varied among cultivars and heat treatments (0.96-2.05 mg.g(-1) DW). In most cases, the heat treatments resulted in a significant decrease in the carotenoids and phenolic compounds contents as well as antioxidant capacity. Processing of flour presented the greatest losses of major carotenoids and phenolics. The phenolic compounds showed more stability than carotenoids after processing. There were significant correlations between the carotenoids and phenolic compounds and the antioxidant capacity.

Vegetables biofortified with iodine: chemical, agronomic and qualitative aspects of raw and fried potatoes

Iodine is an essential microelement for human health because it is a constituent of the thyroid hormones that regulate growth and development of the organism. Iodine Deficiency Disorders (IDDs) are believed to be one of the commonest preventable human health problems in the world today, according to the World Health Organization: that diseases include endemic goiter, cretinism and fetal abnormalities, among others, and they are caused by lack of iodine in the diet, that is the main source of iodine. Since iodine intake from food is not enough respect to human needs, this can be remedied through dietary diversification, mineral supplementation, food fortification, or increasing the concentration and/or bioavailability of mineral elements in the edible portions of crops through agricultural intervention or genetic selection (biofortification). The introduction of iodized salt is a strategy widely used and accepted to eradicate iodine deficiency, because it is an inexpensive source of stable iodine. Since the intake of salt, though iodized, must still be limited according to the risk of cardiovascular disease, so the increase of iodine content in plants for the production of functional foods is representing a field of study of particular interest and a potential market. In Italy potatoes enriched with iodine are produced by a patented procedure of agronomic biofortification for the fresh market since several years, furthermore they are recently accepted and recommended by Italian Thyroid Association, as an alternative source of iodine. Researches performed during the PhD course intended to characterize this innovative vegetables products, focusing the attention on different aspects, such as chemistry, agriculture, and quality of fresh and fried potatoes. For this purpose, lipid fraction of raw material was firstly investigated, in order to assess whether the presence of iodine in plant metabolism can affect fatty acid or sterol biosynthesis, according to the hypothesis that iodine can be bounded to polyunsaturated fatty acids of cell membranes, protecting them from peroxydation; phytosterols of plant sterol are also studied because their importance in reducing serum cholesterol, especially in potato plant sterols are also involved in synthesis of glycoalkaloid, a family of steroidal toxic secondary metabolites present in plants of the Solanaceae family. To achieve this goal chromatographic analytical techniques were employed to identify and quantify fatty acids and sterols profile of common and iodine enriched row potatoes. Another aim of the project was to evaluate the effects of frying on the quality of iodine-enriched and common potatoes. Since iodine-enriched potatoes are nowadays produced only for the fresh market, preliminary trials of cultivation under controlled environment were carried out to verify if potato varieties suitable for processing were able to absorb and accumulate iodine in the tuber. In a successive phase, these varieties were grown in the field, to evaluate their potential productivity and quality at harvest and after storage. The best potato variety to be destined for processing purposes, was finally subjected to repeated frying cycles; the effects of lipid oxidation on the composition and quality of both potatoes and frying oil bath were evaluated by chromatographic and spectrophotometric analytical techniques. Special attention were paid on volatile compounds of fried potatoes.