Differences in metabolic and physiological responses between local and widespread grapevine cultivars underwater deficit stress

Climate change forecasts suggest temperature increases and lower rainfall rates, both of which challenge viticulture, particularly in semi-arid areas where water availability is critical. In this scenario, tlx-use of tlx-genetic variability in grapevine varieties reported around the world represents an important strategy for the selection of climate-resilient cultivars. In this work, physiological and metabolomics analyses were conducted to Compare the water deficit stress (VVIJS) responses of red and white, local and widespread grapevines cultivars. Leaf gas exchange, water use efficiency (WUK) and water relation parameters were determined in plants under well-watered and WDS conditions alongside assessment of the levels of foliar primary metabolites using gas-chromatography coupled to mass-spectrometry. Results denote that red and white local cultivars displayed more adapted physiological performance under WDS as Compared to the widely-distributed ones. Multivariate analyses and specific changes in leaf primary metabolites indicate genotype-specific responses of local cultivars as Compared to widespread ones. Differences in ascorbate-related and shikimate/phenylpropanoid metabolism could explain the better physiological performance under WDS in red local as Compared to widespread cultivars. On the other hand, coordinated changes in respiratory- A nd stress-related sugars and amino acids Could underlie the better WUK under WDS in tlx-white local Cultivar. All these results suggest several metabolic targets that Could be useful as metabolic markers or for metabolic engineering in grapevine breeding programs to improve drought tolerance

Light signals generated by vegetation shade facilitate acclimation to low light in shade-avoider plants

[EN] When growing in search for light, plants can experience continuous or occasional shading by other plants. Plant proximity causes a decrease in the ratio of R to far-red light (low R:FR) due to the preferential absorbance of R light and reflection of FR light by photosynthetic tissues of neighboring plants. This signal is often perceived before actual shading causes a reduction in photo-synthetically active radiation (low PAR). Here, we investigated how several Brassicaceae species from different habitats respond to low R:FR and low PAR in terms of elongation, photosynthesis, and photoacclimation. Shade-tolerant plants such as hairy bittercress (Cardamine hirsuta) displayed a good adaptation to low PAR but a poor or null response to low R:FR exposure. In contrast, shade-avoider species, such as Arabidopsis (Arabidopsis thaliana), showed a weak photosynthetic performance under low PAR but they strongly elongated when exposed to low R:FR. These responses could be genetically uncoupled. Most interestingly, exposure to low R:FR of shade-avoider (but not shade-tolerant) plants improved their photoacclimation to low PAR by triggering changes in photosynthesis-related gene expression, pigment accumulation, and chloroplast ultrastructure. These results indicate that low R:FR signaling unleashes molecular, metabolic, and developmental responses that allow shade-avoider plants (including most crops) to adjust their photosynthetic capacity in anticipation of eventual shading by nearby plants.L.M. received a predoctoral fellowships from La Caixa Foundation (INPhINIT fellowship LCF/BQ/IN18/11660004). W.Q. is a recipient of a predoctoral Chinese Scholarship Council (CSC) fellowship. A.I.-S. is supported by a predoctoral fellowship from MICINN (PRE2018-083610). I.F.-S. has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no. 753301. Our research is supported by grants from MICINN-FEDER (BIO2017-85316-R, and BIO2017-84041-P) and AGAUR (2017-SGR1211, 2017-SGR710 and Xarba) to J.F.M.-G. and M.R.-C. We also acknowledge the support of the MINECO for the "Centro de Excelencia Severo Ochoa 2016-2019" award SEV-2015-0533 and by the CERCA Programme/Generalitat de Catalunya.Morelli, L.; Paulisic, S.; Qin, W.; Iglesias-Sanchez; Roig-Villanova, I.; Florez-Sarasa, I.; Rodriguez Concepción, M.... (2021). Light signals generated by vegetation shade facilitate acclimation to low light in shade-avoider plants. Plant Physiology (Online). 186(4):2137-2151. https://doi.org/10.1093/plphys/kiab206S21372151186

Different metabolic roles for alternative oxidase in leaves of palustrine and terrestrial species

The alternative oxidase pathway (AOP) is associated with excess energy dissipation in leaves of terrestrial plants. To address whether this association is less important in palustrine plants, we compared the role of AOP in balancing energy and carbon metabolism in palustrine and terrestrial environments by identifying metabolic relationships between primary carbon metabolites and AOP in each habitat. We measured oxygen isotope discrimination during respiration, gas exchange, and metabolite profiles in aerial leaves of ten fern and angiosperm species belonging to five families organized as pairs of palustrine and terrestrial species. We performed a partial least square model combined with variable importance for projection to reveal relationships between the electron partitioning to the AOP (τa) and metabolite levels. Terrestrial plants showed higher values of net photosynthesis (AN) and τa, together with stronger metabolic relationships between τa and sugars, important for water conservation. Palustrine plants showed relationships between τa and metabolites related to the shikimate pathway and the GABA shunt, to be important for heterophylly. Excess energy dissipation via AOX is less crucial in palustrine environments than on land. The basis of this difference resides in the contrasting photosynthetic performance observed in each environment, thus reinforcing the importance of AOP for photosynthesis.This work was mainly supported by Ministerio de Economía y Competitividad (MINECO, Spain) (project PGC2018-093824-B-C41) and the ERDF (FEDER). Others funding were provided by FONDECYT No. 1191118 from National Agency for Research and Development (ANID) and the Chilean Scholarship Program/Becas de doctorado nacional/2017–21180329, the European Union’s Horizon 2020 Research and Innovation Program under the Marie Skłodowska-Curie grant agreement no. 753301, the ‘Ramon y Cajal’ contract RYC2019-027244-I/AEI/10.13039/501100011033 and the European Social Fund.Peer reviewe

The Lack of Mitochondrial Thioredoxin TRXo1 Affects In Vivo Alternative Oxidase Activity and Carbon Metabolism under Different Light Conditions

International audienceThe alternative oxidase (AOX) constitutes a nonphosphorylating pathway of electron transport in the mitochondrial respiratory chain that provides flexibility to energy and carbon primary metabolism. Its activity is regulated in vitro by the mitochondrial thioredoxin (TRX) system which reduces conserved cysteines residues of AOX. However, in vivo evidence for redox regulation of the AOX activity is still scarce. In the present study, the redox state, protein levels and in vivo activity of the AOX in parallel to photosynthetic parameters were determined in Arabidopsis knockout mutants lacking mitochondrial trxo1 under moderate (ML) and high light (HL) conditions, known to induce in vivo AOX activity. In addition, 13C- and 14C-labeling experiments together with metabolite profiling were performed to better understand the metabolic coordination between energy and carbon metabolism in the trxo1 mutants. Our results show that the in vivo AOX activity is higher in the trxo1 mutants at ML while the AOX redox state is apparently unaltered. These results suggest that mitochondrial thiol redox systems are responsible for maintaining AOX in its reduced form rather than regulating its activity in vivo. Moreover, the negative regulation of the tricarboxylic acid cycle by the TRX system is coordinated with the increased input of electrons into the AOX pathway. Under HL conditions, while AOX and photosynthesis displayed similar patterns in the mutants, photorespiration is restricted at the level of glycine decarboxylation most likely as a consequence of redox imbalance

Cytochrome c Deficiency Differentially Affects the In Vivo Mitochondrial Electron Partitioning and Primary Metabolism Depending on the Photoperiod

Plant respiration provides metabolic flexibility under changing environmental conditions by modulating the activity of the nonphosphorylating alternative pathways from the mitochondrial electron transport chain, which bypass the main energy-producing components of the cytochrome oxidase pathway (COP). While adjustments in leaf primary metabolism induced by changes in day length are well studied, possible differences in the in vivo contribution of the COP and the alternative oxidase pathway (AOP) between different photoperiods remain unknown. In our study, in vivo electron partitioning between AOP and COP and expression analysis of respiratory components, photosynthesis, and the levels of primary metabolites were studied in leaves of wild-type (WT) plants and cytochrome c (CYTc) mutants, with reduced levels of COP components, under shortand long-day photoperiods. Our results clearly show that differences in AOP and COP in vivo activities between WT and cytc mutants depend on the photoperiod likely due to energy and stress signaling constraints. Parallel responses observed between in vivo respiratory activities, TCA cycle intermediates, amino acids, and stress signaling metabolites indicate the coordination of different pathways of primary metabolism to support growth adaptation under different photoperiods.info:eu-repo/semantics/publishedVersio

Overexpression of thioredoxin m in chloroplasts alters carbon and nitrogen partitioning in tobacco

In plants, there is a complex interaction between carbon (C) and nitrogen (N) metabolism, and its coordination is fundamental for plant growth and development. Here, we studied the influence of thioredoxin (Trx) m on C and N partitioning using tobacco plants overexpressing Trx m from the chloroplast genome. The transgenic plants showed altered metabolism of C (lower leaf starch and soluble sugar accumulation) and N (with higher amounts of amino acids and soluble protein), which pointed to an activation of N metabolism at the expense of carbohydrates. To further delineate the effect of Trx m overexpression, metabolomic and enzymatic analyses were performed on these plants. These results showed an up-regulation of the glutamine synthetase-glutamate synthase pathway; specifically tobacco plants overexpressing Trx m displayed increased activity and stability of glutamine synthetase. Moreover, higher photorespiration and nitrate accumulation were observed in these plants relative to untransformed control plants, indicating that overexpression of Trx m favors the photorespiratory N cycle rather than primary nitrate assimilation. Taken together, our results reveal the importance of Trx m as a molecular mediator of N metabolism in plant chloroplasts.info:eu-repo/semantics/publishedVersio

Decreased levels of Thioredoxin o1 influences stomatal development and aperture but not Photosynthesis under non-stress and saline conditions

Salinity has a negative impact on plant growth, with photosynthesis being downregulated partially due to osmotic effect and enhanced cellular oxidation. Redox signaling contributes to the plant response playing thioredoxins (TRXs) a central role. In this work we explore the potential contribution of Arabidopsis TRXo1 to the photosynthetic response under salinity analyzing Arabidopsis wild-type (WT) and two Attrxo1 mutant lines in their growth under short photoperiod and higher light intensity than previous reported works. Stomatal development and apertures and the antioxidant, hormonal and metabolic acclimation are also analyzed. In control conditions mutant plants displayed less and larger developed stomata and higher pore size which could underlie their higher stomatal conductance, without being affected in other photosynthetic parameters. Under salinity, all genotypes displayed a general decrease in photosynthesis and the oxidative status in the Attrxo1 mutant lines was altered, with higher levels of H2O2 and NO but also higher ascorbate/glutathione (ASC/GSH) redox states than WT plants. Finally, sugar changes and increases in abscisic acid (ABA) and NO may be involved in the observed higher stomatal response of the TRXo1-altered plants. Therefore, the lack of AtTRXo1 affected stomata development and opening and the mutants modulate their antioxidant, metabolic and hormonal responses to optimize their adaptation to salinity.info:eu-repo/semantics/publishedVersio

In Vivo Metabolic Regulation of Alternative Oxidase under Nutrient Deficiency—Interaction with Arbuscular Mycorrhizal Fungi and Rhizobium Bacteria

The interaction of the alternative oxidase (AOX) pathway with nutrient metabolism is important for understanding how respiration modulates ATP synthesis and carbon economy in plants under nutrient deficiency. Although AOX activity reduces the energy yield of respiration, this enzymatic activity is upregulated under stress conditions to maintain the functioning of primary metabolism. The in vivo metabolic regulation of AOX activity by phosphorus (P) and nitrogen (N) and during plant symbioses with Arbuscular mycorrhizal fungi (AMF) and Rhizobium bacteria is still not fully understood. We highlight several findings and open questions concerning the in vivo regulation of AOX activity and its impact on plant metabolism during P deficiency and symbiosis with AMF. We also highlight the need for the identification of which metabolic regulatory factors of AOX activity are related to N availability and nitrogen-fixing legume-rhizobia symbiosis in order to improve our understanding of N assimilation and biological nitrogen fixation.FONDECYT from National Agency for Research and Development (ANID) 1191118Chilean Scholarship Program/Becas de doctorado nacional/2017 21180329European Union (EU) 75330

Synthetic conversion of leaf chloroplasts into carotenoid-rich plastids reveals mechanistic basis of natural chromoplast development

[EN] Plastids, the defining organelles of plant cells, undergo physiological and morphological changes to fulfill distinct biological functions. In particular, the differentiation of chloroplasts into chromoplasts results in an enhanced storage capacity for carotenoids with industrial and nutritional value such as beta-carotene (provitamin A). Here, we show that synthetically inducing a burst in the production of phytoene, the first committed intermediate of the carotenoid pathway, elicits an artificial chloroplast-to-chromoplast differentiation in leaves. Phytoene overproduction initially interferes with photosynthesis, acting as a metabolic threshold switch mechanism that weakens chloroplast identity. In a second stage, phytoene conversion into downstream carotenoids is required for the differentiation of chromoplasts, a process that involves a concurrent reprogramming of nuclear gene expression and plastid morphology for improved carotenoid storage. We hence demonstrate that loss of photosynthetic competence and enhanced production of carotenoids are not just consequences but requirements for chloroplasts to differentiate into chromoplasts.We greatly thank Jaume F. Martinez-Garcia and Ralf Welsch for fruitful discussions on the manuscript; Ralf Welsch and Li Li for providing seeds of the Arabidopsis ccd1 ccd4 and ator atorl mutants, respectively; Juan Jose Lopez-Moya and Maria Luisa Domingo-Calap for the gift of the HcProWMV-pGWB702 vector; and M. Rosa Rodriguez-Goberna for excellent technical support. The help of Marti Bernardo, Fidel Lozano, Lidia Jimenez, and members of the CRAG core facilities is also appreciated. This work was funded by the European Regional Development Fund and Spanish Agencia Estatal de Investigacion Grants BIO2017-84041-P, BIO2017-83184-R, BIO2017-90877-REDT, BES-2017-080652, and AGL2017-85563-C2-1-R; Ministry of Education, Culture and Sports Grants AP2012-3751 and FPU16/04054; and Generalitat de Catalunya Grant 2017SGR-710. We also thank the financial support of the European Union's Horizon 2020 (EU-H2020) COST Action CA15136 (EuroCaroten) and Marie S. Curie Action (MSCA) 753301 (Arcatom), the Severo Ochoa Programme for Centres of Excellence in R&D 2016-2019 Grant SEV-2015-0533 and the Generalitat de Catalunya CERCA Programme (to CRAG). B.L. is supported by grants from the CSIRO Synthetic Biology Future Science Platform and Macquarie University. L.M. is supported by La Caixa Foundation PhD INPhINIT Fellowship LCF/BQ/IN18/11660004, which received funding from the EU-H2020 through MSCA Grant 713673. A.R.F. is supported by Deutsche Forschungsgemeinschaft Grant DFG TRR 175.Llorente, B.; Torres-Montilla, S.; Morelli, L.; Florez-Sarasa, I.; Matus, JT.; Ezquerro, M.; D'andrea, L.... (2020). Synthetic conversion of leaf chloroplasts into carotenoid-rich plastids reveals mechanistic basis of natural chromoplast development. Proceedings of the National Academy of Sciences of the United States of America (Online). 117(35):21796-21803. https://doi.org/10.1073/pnas.2004405117S21796218031173