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Aluminum (Al) is an important factor that limits plant growth under acidic soil conditions. However, several plant species developed distinct mechanisms that limit the damage caused by high Al concentrations. In highbush blueberry (Vaccinium corymbosum), the Al resistance mechanisms are not fully understood. This study was designed to evaluate the effect of Al toxicity on roots and leaves of highbush blueberry genotypes with contrasting Al resistance [Star (Al-sensitive) and Camellia and Cargo (Al-resistant)] and identify the main molecular and physiological strategies underpinning adaptive Al stress responses in nutrient solution. After 48 h of Al treatment, the reduced form of ascorbate (ASC) was higher in roots, but unchanged in leaves of Cargo and Camellia genotypes compared to the control. We also observed decreased root exudation of oxalate in the Al-treated sensitive cultivar Star throughout the treatment period. However, in the resistant cultivar (Camellia), the exudation of oxalate increased 2.4- and 2.8-fold at 24 and 48 h, respectively. Al treatment differentially affected the enzyme activity and gene expression of the tricarboxylic acid (TCA) cycle enzymes. NAD-dependent malate dehydrogenase (NAD-MDH) expression in roots of cultivar Cargo was reduced at 24 h and increased at 48 h, whereas in leaves the expression was higher at 24 h and decreased at 48 h compared to the control. Citrate synthase (CS) activity in Al-resistant Cargo roots diminished at 24 h, increasing afterwards, without variation in the CS gene expression, compared with the initial time point (t = 0). In Al-resistant Camellia roots, the gene expression and the activity of CS decreased during Al exposure. NADP-dependent malate dehydrogenase (NADP-MDH) activity showed increased activity and gene expression at 24 h, in the leaves of cultivar Cargo, whereas in roots the gene expression decreased, but the activation state of NADP-MDH increased. The expression of genes encoding TCA cycle enzymes did not differ significantly in the Al-sensitive cultivar Star during Al exposure. In conclusion, the exudation of organic acid anions, particularly oxalate, plays an important role in Al resistance of highbush blueberry genotypes whilst elevated levels of ASC in roots, also contribute to the Al-resistance mechanisms exhibited by genotypes Camellia and Cargo., This work was supported by FONDECYT Initiation N° 11160355 and FONDECYT Regular N° 1171286 projects (FONDECYT, Chile). Research fellowships granted by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, Brazil) to R.P.O.G., J.R.V. and A.N.N. are also gratefully acknowledged.

Cassava is an important staple crop in sub‐Saharan Africa, due to its high productivity even on nutrient poor soils. The metabolic characteristics underlying this high productivity are poorly understood including the mode of photosynthesis, reasons for the high rate of photosynthesis, the extent of source/sink limitation, the impact of environment, and the extent of variation between cultivars. Six commercial African cassava cultivars were grown in a greenhouse in Erlangen, Germany, and in the field in Ibadan, Nigeria. Source leaves, sink leaves, stems and storage roots were harvested during storage root bulking and analyzed for sugars, organic acids, amino acids, phosphorylated intermediates, minerals, starch, protein, activities of enzymes in central metabolism and yield traits. High ratios of RuBisCO:phosphoenol pyruvate carboxylase activity support a C3 mode of photosynthesis. The high rate of photosynthesis is likely to be attributed to high activities of enzymes in the Calvin–Benson cycle and pathways for sucrose and starch synthesis. Nevertheless, source limitation is indicated because root yield traits correlated with metabolic traits in leaves rather than in the stem or storage roots. This situation was especially so in greenhouse‐grown plants, where irradiance will have been low. In the field, plants produced more storage roots. This was associated with higher AGPase activity and lower sucrose in the roots, indicating that feedforward loops enhanced sink capacity in the high light and low nitrogen environment in the field. Overall, these results indicated that carbon assimilation rate, the K battery, root starch synthesis, trehalose, and chlorogenic acid accumulation are potential target traits for genetic improvement., The Plant Journal, 102 (6), ISSN:0960-7412, ISSN:1365-313X

Cassava plays an important role as a staple food for more than 800 million people in the world due to its ability to maintain relatively high productivity even in nutrient-depleted soils. Even though cassava has been the focus of several breeding programs and has become a strong focus of research in the last few years, relatively little is currently known about its metabolism and metabolic composition in different tissues. In this article, the absolute content of sugars, organic acids, amino acids, phosphorylated intermediates, minerals, starch, carotenoids, chlorophylls, tocopherols, and total protein as well as starch quality is described based on multiple analytical techniques, with protocols specifically adjusted for material from different cassava tissues. Moreover, quantification of secondary metabolites relative to internal standards is presented using both non-targeted and targeted metabolomics approaches. The protocols have also been adjusted to apply to freeze-dried material in order to allow processing of field harvest samples that typically will require long-distance transport., Current protocols in plant biology, 4 (4)

Thiamin pyrophosphate (TPP) is the active form of vitamin B1 and works as an essential cofactor for enzymes in key metabolic pathways, such as the tricarboxylic acid (TCA) cycle and the pentose phosphate pathway. Although its action as a coenzyme has been well documented, the roles of TPP in plant metabolism are still not fully understood. Here, we investigated the functions of TPP in the regulation of the metabolic networks during photoperiod transition using previously described Arabidopsis (Arabidopsis thaliana) riboswitch mutant plants, which accumulate thiamin vitamers. The results show that photosynthetic and metabolic phenotypes of TPP riboswitch mutants are photoperiod dependent. Additionally, the mutants are more distinct from control plants when plants are transferred from a short-day to a long-day photoperiod, suggesting that TPP also plays a role in metabolic acclimation to the photoperiod. Control plants showed changes in the amplitude of diurnal oscillation in the levels of metabolites, including glycine, maltose, and fumarate, following the photoperiod transition. Interestingly, many of these changes are not present in TPP riboswitch mutant plants, demonstrating their lack of metabolic flexibility. Our results also indicate a close relationship between photorespiration and the TCA cycle, as TPP riboswitch mutants accumulate less photorespiratory intermediates. This study shows the potential role of vitamin B1 in the diurnal regulation of central carbon metabolism in plants and the importance of maintaining appropriate cellular levels of thiamin vitamers for the plant's metabolic flexibility and ability to acclimate to an altered photoperiod. ispartof: PLANT PHYSIOLOGY vol:180 issue:1 pages:185-197 ispartof: location:United States status: published

Cassava is an important staple crop in sub-Saharan Africa, due to its high productivity even on nutrient poor soils. The metabolic characteristics underlying this high productivity are poorly understood including the mode of photosynthesis, reasons for the high rate of photosynthesis, the extent of source/sink limitation, the impact of environment, and the extent of variation between cultivars. Six commercial African cassava cultivars were grown in the greenhouse in Erlangen, Germany and the field in Ibadan, Nigeria. Source leaves, sink leaves, stems and storage roots were harvested during storage root bulking and analyzed for sugars, organic acids, amino acids, phosphorylated intermediates, minerals, starch, protein, activities of enzymes in central metabolism and yield traits. High ratios of Rubisco:phosphoenolpyruvate carboxylase activity support a C3 mode of photosynthesis. The high rate of photosynthesis is likely attributed to high activities of enzymes in the Calvin-Benson cycle and pathways for sucrose and starch synthesis. Nevertheless, source limitation is indicated because root yield traits correlated with metabolic traits in leaves rather than in the stem or storage roots. This was especially so in greenhouse-grown plants, where irradiance will have been low. In the field, plants produced more storage roots. This was associated with higher AGPase activity and lower sucrose in the roots, indicating that feedforward loops enhance sink capacity in the high light and low nitrogen environment in the field. Overall, the results indicate that carbon assimilation rate, the K battery, root starch synthesis, trehalose, and chlorogenic acid accumulation are potential target traits for genetic improvement.

To identify genomic regions involved in the regulation of fundamental physiological processes such as photosynthesis and respiration, a population of Solanum pennellii introgression lines was analyzed. We determined phenotypes for physiological, metabolic, and growth related traits, including gas exchange and chlorophyll fluorescence parameters. Data analysis allowed the identification of 208 physiological and metabolic quantitative trait loci with 33 of these being associated to smaller intervals of the genomic regions, termed BINs. Eight BINs were identified that were associated with higher assimilation rates than the recurrent parent M82. Two and 10 genomic regions were related to shoot and root dry matter accumulation, respectively. Nine genomic regions were associated with starch levels, whereas 12 BINs were associated with the levels of other metabolites. Additionally, a comprehensive and detailed annotation of the genomic regions spanning these quantitative trait loci allowed us to identify 87 candidate genes that putatively control the investigated traits. We confirmed 8 of these at the level of variance in gene expression. Taken together, our results allowed the identification of candidate genes that most likely regulate photosynthesis, primary metabolism, and plant growth and as such provide new avenues for crop improvement. Instituto de Biotecnología Fil: Oliveira Silva, Franklin Magnum de. Universidade Federal de Viçosa. Departamento de Biologia Vegetal. Max‐Planck Partner Group; Brasil Fil: Lichtenstein, Gabriel. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Biotecnología; Argentina Fil: Lichtenstein, Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Alseekh, Saleh. Max Planck Institute of Molecular Plant Physiology. Department of Molecular Physiology; Alemania Fil: Rosado‐Souza, Laise. Max Planck Institute of Molecular Plant Physiology; Alemania Fil: Conte, Mariana. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Biotecnología; Argentina Fil: Conte, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Fuentes Suguiyama, Vanessa. Universidade Federal do ABC; Brasil Fil: Lira, Bruno Silvestre. Universidade de São Pablo. Instituto de Biociencias. Departamento de Botânica; Brasil Fil: Fanourakis, Dimitrios. Department of Viticulture, Floriculture, Vegetable Crops and Plant Protection; Grecia Fil: Usadel, Björn. Rheinisch-Westfälische Technische Hochschule Aachen University. Institute for Botany and Molecular Genetics (IBMG). Institute for Biology I; Alemania Fil: Usadel, Björn. Forschungszentrum Jülich. Institut für Bio- und Geowissenschaften 2 (IBG-2); Alemania Fil: Lopes Bhering, Leonardo. Universidade Federal de Viçosa. Departamento de Biologia Geral; Brasil Fil: DaMatta, Fábio M. Universidade Federal de Viçosa. Departamento de Biologia Vegetal; Brasil Fil: Sulpice, Ronan. National University of Ireland Galway. Plant & Agribiosiences. Plant and AgriBiosciences Research Centre. Plant Systems Biology Lab; Irlanda Fil: Araújo, Wagner L. Universidade Federal de Viçosa. Departamento de Biologia Vegetal. Max‐Planck Partner Group; Brasil Fil: Rossi, Magdalena. Universidade de São Pablo. Instituto de Biociencias. Departamento de Botânica; Brasil Fil: de Setta, Nathalia. Universidade Federal do ABC; Brasil Fil: Fernie, Alisdair R. Max Planck Institute of Molecular Plant Physiology. Department of Molecular Physiology; Alemania Fil: Carrari, Fernando. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Biotecnología; Argentina Fil: Carrari, Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Fisiología, Biología Molecular y Neurociencias; Argentina Fil: Nunes Nesi, Adriano. Universidade Federal de Viçosa. Departamento de Biologia Vegetal. Max‐Planck Partner Group; Brasil

Carbohydrates catabolized via respiratory processes are not only used for energy production but also for biosynthesis of cellular components including soluble molecules (sugars, amino acids, organic acids, and their derivatives) and insoluble macromolecules (proteins, starch, and cell wall). Radiotracer experiments using 14C-labeled glucose provide a global picture of the fate of respired carbon in the metabolic network. This method is based on a chemical fractionation of biomolecules in 14C-glucose fed plant materials and the subsequent determination of radioactivity in each fraction. Metabolic flux into each fraction can be estimated from the specific activity of the hexose phosphate pool. Here, we describe the procedure for glucose metabolism in potato tuber but similar protocols can be adopted for various plant organs and substrates.

Collectively, the results presented improve upon the utility of an important genetic resource and attest to a complex genetic basis for differences in both leaf metabolism and fruit morphology between natural populations. Diversity of accessions within the same species provides an alternative method to identify physiological and metabolic traits that have large effects on growth regulation, biomass and fruit production. Here, we investigated physiological and metabolic traits as well as parameters related to plant growth and fruit production of 49 phenotypically diverse pepper accessions of Capsicum chinense grown ex situ under controlled conditions. Although single-trait analysis identified up to seven distinct groups of accessions, working with the whole data set by multivariate analyses allowed the separation of the 49 accessions in three clusters. Using all 23 measured parameters and data from the geographic origin for these accessions, positive correlations between the combined phenotypes and geographic origin were observed, supporting a robust pattern of isolation-by-distance. In addition, we found that fruit set was positively correlated with photosynthesis-related parameters, which, however, do not explain alone the differences in accession susceptibility to fruit abortion. Our results demonstrated that, although the accessions belong to the same species, they exhibit considerable natural intraspecific variation with respect to physiological and metabolic parameters, presenting diverse adaptation mechanisms and being a highly interesting source of information for plant breeders. This study also represents the first study combining photosynthetic, primary metabolism and growth parameters for Capsicum to date.

Iron toxicity is the most important stressor of rice in many lowland environments worldwide. Rice cultivars differ widely in their ability to tolerate excess iron. A physiological evaluation of iron toxicity in rice was performed using non-invasive photosynthesis, photorespiration and chlorophyll a fluorescence imaging measurements and chlorophyll content determination by SPAD. Four rice cultivars (BR IRGA 409; BR IRGA 412; BRA 041171 and BRA 041152) from the Brazilian breeding programs were used. Fe 2+ was supplied in the nutrient solution as Fe–EDTA (0.019, 4, 7 and 9 mM). Increases in shoot iron content due to Fe 2+ treatments led to changes in most of the non-invasive physiological variables assessed. The reduction in rice photosynthesis can be attributed to stomatal limitations at moderate Fe 2+ doses (4 mM) and both stomatal and non-stomatal limitations at higher doses. Photorespiration was an important sink for electrons in rice cultivars under iron excess. A decreased chlorophyll content and limited photochemical ability to cope with light excess were characteristic of the more sensitive and iron accumulator cultivars (BRA 041171 and BRA 041152). Chlorophyll fluorescence imaging revealed a spatial heterogeneity of photosynthesis under excessive iron concentrations. The results showed the usefulness of non-invasive physiological measurements to assess differences among cultivars. The contributions toward understanding the rice photosynthetic response to toxic levels of iron in the nutrient solution are also discussed.