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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

Ascorbate (vitamin C) plays essential roles in stress resistance, development, signaling, hormone biosynthesis and regulation of gene expression; however, little is known about its biosynthesis in algae. In order to provide experimental proof for the operation of the Smirnoff-Wheeler pathway described for higher plants and to gain more information on the regulation of ascorbate biosynthesis in Chlamydomonas reinhardtii, we targeted the VTC2 gene encoding GDP-l-galactose phosphorylase using artificial microRNAs. Ascorbate concentrations in VTC2 amiRNA lines were reduced to 10% showing that GDP-l-galactose phosphorylase plays a pivotal role in ascorbate biosynthesis. The VTC2 amiRNA lines also grow more slowly, have lower chlorophyll content, and are more susceptible to stress than the control strains. We also demonstrate that: expression of the VTC2 gene is rapidly induced by H2 O2 and 1 O2 resulting in a manifold increase in ascorbate content; in contrast to plants, there is no circadian regulation of ascorbate biosynthesis; photosynthesis is not required per se for ascorbate biosynthesis; and Chlamydomonas VTC2 lacks negative feedback regulation by ascorbate in the physiological concentration range. Our work demonstrates that ascorbate biosynthesis is also highly regulated in Chlamydomonas albeit via mechanisms distinct from those previously described in land plants.

Plants often modify their metabolism in order to regain homeostasis and maintain survival in the face of stressful conditions. Here, two species of eucalyptus, E. globulus and E. grandis (adapted and non-adapted to low temperature, respectively), were exposed to either 10 °C or 25 °C over 24 h, and changes in gene expression and metabolite levels were analyzed. The aim of this experiment was to investigate the dynamic of short period changes in the energy metabolism of source (leaves) and sink (stem) tissues in these contrasting species regarding low temperature. We expected to observe a distinct pattern on carbon metabolism and source-to-sink relationship between both species which would be related to their different vegetative responses when facing low temperatures. In that way, E. globulus plants showed a differential expression in leaves and stems of SnRK1 genes system (responsible for energy availability control in plants), that was strongly associated to the changes in carbon metabolism and the main difference between the response when both species face cold. Taken together, the results suggest that low temperatures (10 °C) are able to increase the sink strength of stem tissues and the carbon assimilation in leaves of E. globulus, supporting a higher vegetative growth rate. In E. grandis, on the other hand, exposure to 10 °C promoted a higher consumption of carbon skeletons without better growth rate as a counterpart, suggesting that under cold conditions, these two eucalyptus species differ in the way they coordinate the interaction between the activation of SnRK1 system and primary metabolism in source and sink tissues.

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

Cell compartmentalization allows incompatible chemical reactions and localised responses to occur simultaneously, however, it also requires a complex system of communication between compartments in order to maintain the functionality of vital processes. It is clear that multiple such signals must exist, yet little is known about the identity of the key players orchestrating these interactions or about the role in the coordination of other processes. Mitochondria and chloroplasts have a considerable number of metabolites in common and are interdependent at multiple levels. Therefore, metabolites represent strong candidates as communicators between these organelles. In this context, vitamins and similar small molecules emerge as possible linkers to mediate metabolic crosstalk between compartments. This review focuses on two vitamins as potential metabolic signals within the plant cell, vitamin C (L-ascorbate) and vitamin B1 (thiamin). These two vitamins demonstrate the importance of metabolites in shaping cellular processes working as metabolic signals during acclimation processes. Inferences based on the combined studies of environment, genotype, and metabolite, in order to unravel signaling functions, are also highlighted.

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.