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Nuclear magnetic resonance metabolomics of iron deficiency in soybean leaves

Publication . Lima, Marta R. M.; Diaz, Sílvia O.; Lamego, Inês; Grusak, Michael A.; Vasconcelos, Marta; Gil, Ana M.

Iron (Fe) deficiency is an important agricultural concern that leads to lower yields and crop quality. A better understanding of the condition at the metabolome level could contribute to the design of strategies to ameliorate Fe-deficiency problems. Fe-sufficient and Fe-deficient soybean leaf extracts and whole leaves were analyzed by liquid 1H nuclear magnetic resonance (NMR) and high-resolution magic-angle spinning NMR spectroscopy, respectively. Overall, 30 compounds were measurable and identifiable (comprising amino and organic acids, fatty acids, carbohydrates, alcohols, polyphenols, and others), along with 22 additional spin systems (still unassigned). Thus, metabolite differences between treatment conditions could be evaluated for different compound families simultaneously. Statistically relevant metabolite changes upon Fe deficiency included higher levels of alanine, asparagine/aspartate, threonine, valine, GABA, acetate, choline, ethanolamine, hypoxanthine, trigonelline, and polyphenols and lower levels of citrate, malate, ethanol, methanol, chlorogenate, and 3-methyl-2-oxovalerate. The data indicate that the main metabolic impacts of Fe deficiency in soybean include enhanced tricarboxylic acid cycle activity, enhanced activation of oxidative stress protection mechanisms and enhanced amino acid accumulation. Metabolites showing accumulation differences in Fe-starved but visually asymptomatic leaves could serve as biomarkers for early detection of Fe-deficiency stress.

2014Journal article

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Cultivar variability of iron uptake mechanisms in rice (Oryza sativa L.)

Publication . Pereira, Margarida P.; Santos, Carla; Gomes, Ana M. P.; Vasconcelos, Marta W.

Rice (Oryza sativa L.) is the most important staple food in the world. It is rich in genetic diversity and can grow in a wide range of environments. Iron (Fe) deficiency is a major abiotic stress in crop production and in aerobic soils, where Fe forms insoluble complexes, and is not readily available for uptake. To cope with Fe deficiency, plants developed mechanisms for Fe uptake, and although rice was described as a Strategy II plant, recent evidence suggests that it is capable of utilizing mechanisms from both Strategies. The main objective of this work was to compare two cultivars, Bico Branco (japonica) and Nipponbare (tropical japonica), to understand if the regulation of Fe uptake mechanisms could be cultivar (cv.) dependent. Plants of both cultivars were grown under Fe-deficient and -sufficient conditions and physiological and molecular responses to Fe deficiency were evaluated. Bico Branco cv. developed more leaf chlorosis and was more susceptible to Fe deficiency, retaining more nutrients in roots, than Nipponbare cv., which translocated more nutrients to shoots. Nipponbare cv. presented higher levels of Fe reductase activity, which was significantly up-regulated by Fe deficiency, and had higher expression levels of the Strategy I-OsFRO2 gene in roots, while Bico Branco cv. induced more genes involved in Strategy II. These new findings show that rice cultivars have different responses to Fe deficiency and that the induction of Strategy I or II may be rice cultivar-dependent, although the utilization of the reduction mechanisms seems to be an ubiquitous advantage.

2014Journal article

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Morpho-physiological parameters affecting iron deficiency chlorosis in soybean (Glycine max L.)

Publication . Vasconcelos, Marta; Grusak, Michael A.

Background and aims Iron deficiency chlorosis (IDC) leads to severe leaf chlorosis, low photosynthetic rates, and yield reductions of several million metric tonnes each year. In order to devise breeding and genetic transformation programs that aim at generating high-yielding and IDC-tolerant soybean lines, it is necessary to better understand the mechanisms that enable tolerant plants to survive under Fe-limiting conditions. Methods An in silico analysis in the USDA soybean collection allowed the identification of a set of novel efficient and inefficient soybean cultivars which can be used in future studies concerning IDC response. Plants were grown in iron deficient and iron sufficient conditions using a bicarbonate system and several IDCrelated aspects were studied. Results A new set of efficient and inefficient soybean lines were identified in silico, and their tolerance to IDC was confirmed under laboratorial conditions. New plant traits that are highly correlated to IDC scoring were identified: a negative correlation was found between SPADvalues and stemweight,weight of the unifoliolates and iron concentration of the first unifoliolates was found; higher SPAD values were correlated with the amount of iron in the first trifoliate leaves. Our data also show that having higher concentrations of iron in the seeds provides increased resistance to IDC. No correlation was found between root iron reductase activity and chlorosis. Conclusions Soybean differential chlorosis susceptibility between different accessions is linked to specific morpho-physiological parameters such as unifoliolate leaf size, stem weigh, concentration of iron in the seeds, and tissue iron partitioning.

2014Journal article

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Transcriptomic analysis of iron deficiency related genes in the legumes

Publication . Santos, Carla S.; Silva, Ana I.; Serrão, Inês; Carvalho, Ana L.; Vasconcelos, Marta W.

Among the mineral elements required by humans, iron (Fe) is the most common cause of nutritional deficiencies, particularly anaemia. Legume plants are extremely important in the world's diet and they are major sources of mineral nutrients. However, when these plant foods are grown in calcareous soil, their production is severely affected by Fe deficiency chlorosis (IDC), and when less Fe is available for absorption, less amount of this element will be available for accumulation in the edible plant parts. As Fe plays critical roles in photosynthesis and respiration, when lacking this element, plants develop chlorosis and their growth is drastically reduced. IDC morphological symptoms were monitored in soybean (Glycine max), common bean (Phaseolus vulgaris) and the model crop barrel medic (Medicago truncatula). When compared to the other two legumes, G. max presented lower Fe-reduction rates and severe chlorosis, associated with lower SPAD values. Transcriptome analysis was performed in roots of the three species when grown in Fe deficiency and Fe sufficiency, and 114,723 annotated genes were obtained for all samples. Four IDC-related genes were up-regulated in common by the three species and can be considered key players involved in the IDC response, namely, metal ligands, transferases, zinc ion binding and metal ion binding genes. With regards to the genes most highly expressed under iron deficiency individually by each species, we found that the most highly expressed genes were a defensin in P. vulgaris, a phosphatase in M. truncatula and a zinc ion binding gene in G. max.

2013Journal article

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Evaluation of chitooligosaccharide application on mineralaccumulation and plant growth in Phaseolus vulgaris

Publication . Chatelain, Philippe G.; Pintado, Manuela E.; Vasconcelos, Marta

tChitooligosaccharides (COS) – water soluble derivatives from chitin, are an interesting group of moleculesfor several biological applications, for they can enter plant cells and bind negatively charged molecules.Several studies reported an enhanced plant growth and higher crop yield due to chitosan application insoil grown plants, but no studies have looked on the effect of COS application on plant mineral nutrientdynamics in hydroponically grown plants. In this study, Phaseolus vulgaris was grown in hydroponicculture and the effect of three different concentrations of COS on plant growth and mineral accumulationwas assessed. There were significant changes in mineral allocations for Mo, B, Zn, P, Pb, Cd, Mn, Fe, Mg,Ca, Cu, Na, Al and K among treatments. Plant morphology was severely affected in high doses of COS,as well as lignin concentration in the stem and the leaves, but not in the roots. Chlorophyll A, B andcarotenoid concentrations did not change significantly among treatments, suggesting that even at higherconcentrations, COS application did not affect photosynthetic pigment accumulation. Plants grown athigh COS levels had shorter shoots and roots, suggesting that COS can be phytotoxic to the plant. Thepresent study is the first detailed report on the effect of COS application on mineral nutrition in plants,and opens the door for future studies that aim at utilizing COS in biofortification or phytoremediationprograms.

2014Journal article

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