Biology subjects

Lunn, J. E.

Publications and source records attributed to Lunn, J. E..

18 recordsLinked to original sources

bioRxiv2026

C4 photosynthetic pathway fluxes in transgenic rice plants

Most land plants photosynthesize using the C3 pathway, in which ribulose bisphosphate carboxylase/oxygenase (Rubisco) fixes CO2 into 3-carbon acids. The C4 pathway, a biochemical CO2-concentrating mechanism that operates in the context of specialized leaf anatomy to concentrate CO2 around Rubisco, is more efficient. Introduction of the C4 pathway into the C3 crop rice could increase yield by 50%. Expression of five C4 enzymes in transgenic rice previously led to flux through the first step. However, there was no evidence for flux later in the cycle. Here we developed new transgenic rice lines and novel protocols to detect C4 cycle activity: CO2 fixation into C4 acids by carboxylation of a C3 compound, decarboxylation, refixation of CO2 by Rubisco, and regeneration of the C3 donor. We demonstrate that these four core C4 reactions are operating in rice, establishing the in vivo flux framework needed to progress towards a functional carbon-concentrating mechanism

plant biology↗

bioRxiv2025

TPS Proteins coordinate plant growth with sugar availability via the SnRK1 Kinase

The ability to sense and respond to nutrients determines adaptation and survival in all organisms. In plants, sucrose stimulates growth and developmental progression via the signalling sugar trehalose 6-phosphate (T6P) which reflects sucrose availability. T6P acts, at least partly, by inhibiting the protein kinase SUCROSE NON-FERMENTING 1 (SNF1)-RELATED KINASE 1 (SnRK1) but the underlying mechanisms are poorly understood. Here, we identify a group of catalytically inactive T6P synthase (TPS) proteins, TPS5/6/7, as important factors for coupling the T6P signal to SnRK1 activity. In Arabidopsis thaliana, lack of TPS5/6/7 causes severe growth defects, particularly in roots. This is accompanied by a metabolic signature that is suggestive of T6P insensitivity and impaired sucrose utilization. Using a combination of genetics, SnRK1 activity assays, and imaging, we demonstrate that the growth defects of the tps5/6/7 mutant are due to SnRK1 misregulation and are reverted by knocking-down SnRK1 in this background. Co-immunoprecipitation assays further show that T6P promotes the interaction of TPS proteins with SnRK1 in a highly specific and dose-dependent manner. Our results support a model where TPS proteins act as T6P sensors, inhibiting non-nuclear SnRK1 activity when sucrose is abundant to promote biosynthetic processes and growth.

plant biology↗

bioRxiv2025

Exploring the diversity of the CO2-concentrating mechanism (CCM) in different C4 subtypes

C4 plants have traditionally been classified into NADP-malic enzyme (NADP-ME), NAD-malic enzyme (NAD-ME) and PEP carboxykinase (PEPCK) subtypes based on the predominant C4-acid decarboxylating enzyme. To investigate the relative contributions of malate and aspartate to C4-pathway fluxes in each subtype, we performed 13CO2 pulse and pulse-chase labelling experiments on four C4 grass species: Zea mays and Setaria viridis (NADP-ME), Panicum miliaceum (NAD-ME) and Megathyrsus maximus (PEPCK). Only a proportion (8-50%) of the total malate pool in the leaves is photosynthetically active whereas essentially all of the aspartate pool is photosynthetically active. Estimates of metabolic fluxes indicate that approximately two thirds of the C4 pathway flux is via malate in Z. mays and the remaining third via aspartate, while in S. viridis 50% of the flux is via malate and 50% via aspartate. In P. miliaceum and M. maximus, 91% and 85% of the flux is via aspartate and the remaining 5% and 15% via malate, respectively. The results reveal greater complexity of C4 pathway fluxes than is usually represented in textbook diagrams, and demonstrate the feasibility of using non-radioactive 13CO2 in pulse-chase labelling experiments to study C4 photosynthesis and to detect C4 pathway fluxes in C3 plants engineered to perform C4 photosynthesis. Highlight StatementPhotosynthetic fluxes in C4 species are more complex than most textbook models show, with malate and aspartate both carrying C4 cycle fluxes in all three subtypes (NADP-ME, NAD-ME and PEPCK).

plant biology↗

bioRxiv2025

Seasonal changes in the physiology and metabolism of grapevine perennating buds

Grapevine (Vitis vinifera L.) buds undergo seasonal dormancy to survive unfavourable conditions and synchronize growth with environmental cues. While dormancy transitions have been widely studied in temperate woody perennials, the physiological and metabolic dynamics underlying these transitions in grapevine remain poorly understood. Our study investigates seasonal changes in the physiology and metabolism of perennating buds in V. vinifera cv. Cabernet Sauvignon, focusing on dormancy depth, respiration, sugar metabolism, and cell cycle activity. We identified three distinct phases of bud quiescence: (i) para-dormancy (early summer), characterized by active metabolism and high levels of tricarboxylic acid cycle intermediates, shikimate, and myo-inositol; (ii) endo-dormancy (late summer to autumn), where dormancy depth peaked in late summer and was marked by reduced respiration and bud water content, and a sharp decline in hexose levels with a concomitant increase in raffinose; and (iii) eco-dormancy (winter to spring), featuring increased respiration, sugar mobilization (notably sucrose, glucose, and trehalose), and reactivation of cell division, with a shift of cells into the G2 phase. Just prior to bud burst, we observed a significant accumulation of sugar-phosphates, providing evidence that supports their role in promoting bud burst also in grapevine. Our findings provide new insights into the biochemical and physiological regulation of bud dormancy and bud burst, contributing to a deeper understanding of dormancy transitions in perennial crops.

plant biology↗

bioRxiv2024

Intercellular compartmentation of trehalose 6-phosphate metabolism in Setaria viridis leaves

Trehalose 6-phosphate (Tre6P) is a signal metabolite that links carbon metabolism with plant development. Our current understanding of Tre6P metabolism and signalling is predominantly based on studies in Arabidopsis thaliana. Some features could be adapted to the specific physiology, anatomy, and life cycle of this C3 eudicot model species, and thus might not be representative of other angiosperms. To better understand Tre6P metabolism in monocot C4 species we used Setaria viridis, which has been widely adopted as a model for the major C4 NADP-malic enzyme subtype crop species, such as maize (Zea mays), sorghum (Sorghum bicolor) and sugarcane (Saccharum officinarum). In this work, we analysed the levels of transcripts encoding Tre6P-related enzymes in different tissues and cell types from S. viridis. The TREHALOSE-6-PHOSPHATE SYNTHASE1 transcript, its encoded protein (TPS1, the enzyme responsible for Tre6P synthesis) and Tre6P were mainly located in bundle sheath cells of S. viridis. Our results show that Tre6P is predominately synthesized and located in bundle sheath and associated cells. HighlightTrehalose 6-phosphate, a sugar signalling metabolite, is mainly present in the bundle sheath cells of Setaria viridis leaves.

plant biology↗

bioRxiv2024

The stress-protectant molecule trehalose mediates fluconazole tolerance in Candida glabrata

The incidence of non-albicans Candida infections has witnessed a substantial rise in recent decades. Candida glabrata (Nakaseomyces glabratus), an opportunistic human fungal pathogen, is accountable for both superficial mucosal and life-threatening bloodstream infections, particularly in immunocompromised individuals. Distinguished by its remarkable resilience to environmental stressors, C. glabrata exhibits intrinsic tolerance to azoles and a high propensity to swiftly develop azole resistance during treatment. The molecular mechanism for the high tolerance is not fully understood. In this work we investigated the possible role of trehalose in this tolerance. We generated mutants in the C. glabrata TPS1, TPS2, and NTH1 genes, encoding trehalose 6-phosphate synthase (Tps1), trehalose 6-phosphate phosphatase (Tps2), and neutral trehalase (Nth1), respectively. As expected, the tps1{Delta} strain cannot grow on glucose. The tps2{Delta} strain demonstrated diminished trehalose accumulation and very high levels of trehalose 6-phosphate (T6P), the biosynthetic intermediate, in comparison to the WT strain. Whereas these higher T6P levels did not affect growth, the lower trehalose levels clearly resulted in lower environmental stress tolerance and a lower susceptibility to fluconazole. More interestingly, the tps2{Delta} strain completely lost tolerance to fluconazole, characterized by the absence of slow growth at supra-MIC concentrations of this drug. All these phenotypes are reversed in the nth1{Delta} strain, which accumulates high levels of trehalose. Our findings underscore the role of trehalose in enabling tolerance towards fluconazole in C. glabrata. We further show that the change in tolerance is a result of the effect that trehalose has on the sterol pattern in the cell, showing that accumulation of toxic sterols correlate with absence of tolerance. Author summaryC. glabrata is a yeast of significant medical importance, known for causing nosocomial outbreaks of invasive candidiasis. Its propensity to develop resistance to antifungal medications, notably azoles such as fluconazole, raises considerable concern. An underlying reason for the rapid development of resistance is its intrinsic tolerance to this drug. The underlying molecular mechanism of tolerance to fluconazole is heavily studied but not understood. This study sheds light on the involvement of trehalose in modulating tolerance to fluconazole. We have elucidated that trehalose serves not only as a protective agent against various stresses but also as a mediator of fluconazole resistance and tolerance. To start elucidating how this may work, we provide data that trehalose (or the enzymes affecting the amount of trehalose in the cell) alters the ergosterol type and level in the cells, thereby affecting tolerance.

microbiology↗

bioRxiv2023

Direct and indirect responses of the Arabidopsis transcriptome to an induced increase in trehalose 6-phosphate

Trehalose 6-phosphate (Tre6P) is an essential signal metabolite that reports and regulates the level of sucrose, linking growth and development to the metabolic status. We hypothesized that Tre6P plays a role in mediating the regulation of gene expression by sucrose. To test this, we performed transcriptomic profiling on Arabidopsis plants that expressed a bacterial trehalose-6-phosphate synthase (TPS) under the control of an ethanol-inducible promoter. Induction led to a 4-fold rise in Tre6P levels, a concomitant decrease in sucrose, and significant changes of over 13,000 transcripts and two-fold or larger changes of over 5000 transcripts. Comparison with nine published responses to sugar availability allowed some of these changes to be linked to the rise in Tre6P, while others were probably due to lower sucrose or other indirect effects. Changes linked to Tre6P included repression of photosynthesis and induction of many growth-related processes including ribosome biogenesis. About 500 starvation-related genes are known to be induced by SUCROSE-NON-FERMENTING-1-RELATED KINASE 1 (SnRK1). They were largely repressed by Tre6P in a manner consistent with Tre6P acting to inhibit SnRK1. SnRK1 also represses many genes that are involved in biosynthesis and growth. These responded to Tre6P in a more complex manner, pointing to Tre6P also interacting with further C-signaling pathways. In addition, elevated Tre6P modified expression of genes encoding regulatory subunits of the SnRK1 complex and TPS class II and FLZ proteins that are thought to modulate SnRK1 function, and genes involved in the circadian clock and in TOR, light, abscisic acid and other hormone signaling. One sentence summaryAn induced increase in trehalose 6-phosphate levels has direct effects on gene expression via inhibition of SUCROSE-NON-FERMENTING-1-RELATED KINASE 1 and interactions with light, circadian clock and phytohormone signaling, and widespread indirect effects on gene expression from reciprocal changes in sucrose levels.

plant biology↗

bioRxiv2023

Spliceosomal complex components are critical for adjusting the C:N balance during high-light acclimation

Plant acclimation to an ever-changing environment is decisive for growth, reproduction and survival. Light availability limits biomass production on both ends of the intensity spectrum. Therefore, the adjustment of plant metabolism is central to high-light (HL) acclimation, and accumulation of photoprotective anthocyanins is commonly observed. However, mechanisms and factors regulating the HL acclimation response are less clear. Two Arabidopsis mutants of spliceosome components exhibiting a pronounced anthocyanin overaccumulation in HL were isolated from a forward genetic screen for new factors crucial for plant acclimation. Time-resolved physiological, transcriptome and metabolome analysis revealed a vital function of the spliceosome components for rapidly adjusting gene expression and metabolism. Deficiency of INCREASED LEVEL OF POLYPLOIDY1 (ILP1), NTC-RELATED PROTEIN1 (NTR1), and PLEIOTROPIC REGULATORY LOCUS1 (PRL1) resulted in a marked overaccumulation of carbohydrates and strongly diminished amino acid biosynthesis in HL. While not generally limited in N-assimilation, ilp1, ntr1, and prl1 mutants showed higher glutamate levels and reduced amino acid biosynthesis in HL. The comprehensive analysis reveals a function of the spliceosome in the conditional regulation of the carbon:nitrogen-balance and the accumulation of anthocyanins during HL acclimation. The importance of gene expression, metabolic regulation, and re-direction of carbon towards anthocyanin biosynthesis for HL acclimation are discussed.

molecular biology↗

bioRxiv2023

S1 basic leucine zipper transcription factors shape plant architecture by controlling C/N partitioning to apical and lateral organs

Plants exhibit an immense plasticity in their architecture. While the impact of hormonal regulation is well-characterised, the importance of sugar-signalling has just recently emerged. Here, we addressed which sugar-signalling components mediate the trade-off between growth of apical versus lateral meristems and how they control organ sink-strength. Thereby, we unravelled a novel developmental function of the sugar-controlled S1 basic-leucine-zipper (S1-bZIP) transcription factors in establishing global source-sink interactions. Applying comprehensive molecular, analytical, and genetic approaches, we demonstrate that S1-bZIPs operate in a redundant manner to control tissue-specific expression of defined SWEET sugar-transporters and the GAT1_2.1 glutaminase. By these means, S1-bZIPs control carbohydrate (C)-channelling from source leaves to apical shoot and root organs and tune systemic organic nitrogen (N)-supply to restrict lateral organ formation by C/N depletion. Knowledge of the underlying mechanisms controlling plant C/N partitioning is of pivotal importance for breeding strategies to generate plants with desired architectural and nutritional characteristics.

plant biology↗

bioRxiv2023

The transcription factor bZIP11 acts antagonistically with trehalose 6-phosphate to inhibit shoot branching

The ontogenetic regulation of shoot branching allows plants to adjust their architecture in accordance with the environment. This process is due to the regulation of axillary bud outgrowth into branches, which can be induced by increasing sugar availability to the buds through decapitation of the shoot tip. Different sugar signalling components have been identified in the induction of shoot branching. However, the molecular components that maintain bud dormancy in response to sugar starvation remain largely unknown. Here, we show at the genetic level that basic leucine zipper 11 (bZIP11), a transcription factor that plays important roles in response to sugar starvation in plants, inhibits shoot branching in Arabidopsis thaliana. Physiology experiments demonstrated that bZIP11 protein levels are decreased by decapitation. Molecular and genetic evidence suggests that bZIP11 acts in a negative feedback loop with trehalose 6-phosphate (Tre6P), a sugar signal that promotes shoot branching. Our data also suggest that the central energy sensor SUCROSE NON-FERMENTING 1 RELATED KINASE1 (SnRK1), alleviates the inhibitory effect of Tre6P on bZIP11 protein accumulation and inhibits shoot branching. Altogether, these data provide a working model that involves bZIP11, Tre6P and SnRK1 in the regulation of shoot branching.

plant biology↗

bioRxiv2023

Sugar signaling modulates SHOOT MERISTEMLESS expression and meristem function in Arabidopsis

In plants, development of all above-ground tissues is controlled by the shoot apical meristem (SAM) which balances cell proliferation and differentiation to allow life-long growth. To maximize fitness and survival, meristem activity is adjusted to the prevailing conditions through a poorly understood integration of developmental signals with environmental and nutritional information. Here, we show that sugar signals influence SAM function by altering the protein levels of SHOOT MERISTEMLESS (STM), a key regulator of meristem maintenance. STM is less abundant in the inflorescence meristems of plants grown or treated under limiting light conditions, with lower STM levels correlating with lower sugar content in these meristems. Additionally, sucrose but not light is sufficient to sustain STM accumulation in excised inflorescences. Plants overexpressing the 1-subunit of SUCROSE-NON-FERMENTING1-RELATED KINASE 1 (SnRK1) accumulate less STM protein under optimal light conditions, despite higher sugar accumulation in the meristem. Furthermore, SnRK11 interacts physically with STM, suggesting a direct local repression. Surprisingly, silencing SnRK1 in the meristem leads to reduced STM expression and severe developmental phenotypes previously associated with STM loss-of-function. Altogether, we demonstrate that sugars promote STM accumulation and that the SnRK1 sugar sensor plays a dual role in the SAM, limiting STM abundance under unfavorable conditions but being required for overall meristem organization and integrity. This highlights the importance of sugars and SnRK1 signaling for the proper coordination of meristem activities.

plant biology↗

bioRxiv2022

Diel fluctuations in in-vivo SnRK1 activity in Arabidopsis rosettes during light-dark cycles

SUCROSE-NON-FERMENTING1 (SNF1)-RELATED KINASE1 (SnRK1) is a central hub in carbon and energy signalling in plants, and is orthologous with SNF1 in yeast and the AMP-ACTIVATED PROTEIN KINASE (AMPK) in animals. Previous studies of SnRK1 relied on in-vitro activity assays or on monitoring the expression of putative marker genes. Neither approach gives unambiguous information about in-vivo SnRK1 activity. We have monitored in-vivo SnRK1 activity using Arabidopsis (Arabidopsis thaliana) reporter lines that express a chimeric polypeptide with a SNF1/SnRK1/AMPK-specific phosphorylation site. We investigated responses during an equinoctial diel cycle, and after perturbing this cycle. As expected, in vivo SnRK1 activity rose towards the end of the night and rose even further when the night was extended. Unexpectedly, although sugars rose after dawn, SnRK1 activity did not decline until about 12 hours into the light period. The sucrose signal trehalose 6-phosphate (Tre6P) has been shown to inhibit SnRK1 in vitro. We introduced the SnRK1 reporter into lines that harboured an inducible TREHALOSE-6-PHOSPHATE SYNTHASE construct. Elevated Tre6P decreased in-vivo SnRK1 activity in the light period, but not at the end of the night. Reporter polypeptide phosphorylation was sometimes negatively correlated with Tre6P, but a stronger and more widespread negative correlation was observed with glucose 6-phosphate. We propose that SnRK1 operates within a network that controls carbon utilization and maintains diel sugar homeostasis, and that Tre6P, hexose phosphates and the circadian clock contribute to regulation of SnRK1 activity in a context-dependent manner, and SnRK1-signalling is further modulated by factors that act downstream of SnRK1. One sentence summaryIn vivo SnRK1 activity shows an unexpected diel response and a complex relationship with trehalose 6-phosphate and other possible metabolic regulators.

plant biology↗

bioRxiv2022

The Arabidopsis transcription factor NLP2 regulates early nitrate responses and integrates nitrate assimilation with energy and carbon skeleton supply

Nitrate signaling improves plant growth under limited nitrate availability and, hence, optimal resource use for crop production. Ongoing work has identified several transcriptional regulators of nitrate signaling, including the Arabidopsis thaliana transcription factor NIN-LIKE PROTEIN 7 (NLP7), but additional regulators likely remain to be identified. Here, we characterized Arabidopsis NLP2 as a master upstream transcriptional regulator of early nitrate responses that interacts with NLP7 in vivo and shares key molecular features such as nitrate-dependent nuclear localization, a DNA binding motif, and some target genes with NLP7. Additional genetic, genomic and metabolic approaches revealed a specific role for NLP2 in the nitrate-dependent regulation of carbon and energy-related processes that likely influence plant growth under distinct nitrogen environments. Our findings highlight the complementarity and specificity of NLP2 and NLP7 in orchestrating a multi-tiered nitrate regulatory network that links nitrate assimilation with carbon and energy metabolism for efficient nitrogen use and biomass production. One-sentence summaryNLP2 and NLP7 orchestrate plant responses to nitrate supply and control nitrate- dependent regulation of carbon and energy metabolism.

plant biology↗

bioRxiv2021

Trehalose-6-phosphate links singlet oxygen-induced signalling with metabolic signalling in Chlamydomonas reinhardtii

Using a novel mutant screen, we identified TREHALOSE 6-PHOSPHATE PHOSPHATASE 1 (TSPP1) as a functional enzyme dephosphorylating trehalose 6-phosphate (Tre6P) to trehalose in Chlamydomonas reinhardtii. The tspp1 knock-out results in reprogramming of the cell metabolism via significantly altered transcriptome. As a secondary effect, tspp1 also shows impairment in 1O2-induced chloroplast retrograde signalling. From transcriptomic analysis and metabolite profiling, we conclude that accumulation or deficiency of certain metabolites directly affect 1O2-signalling. 1O2-inducible GLUTATHIONE PEROXIDASE 5 (GPX5) gene expression is suppressed by increased content of fumarate, an intermediate in the tricarboxylic acid cycle (TCA cycle) in mitochondria and dicarboxylate metabolism in the cytosol, while it is promoted by another TCA cycle intermediate, aconitate. Furthermore, genes encoding known essential components of chloroplast-to-nucleus 1O2-signalling, PSBP2, MBS, and SAK1, show decreased transcript levels in the tspp1 mutant, which can be rescued by exogenous application of aconitate. We demonstrate that chloroplast retrograde signalling involving 1O2 depends on mitochondrial and cytosolic processes and that the metabolic status of the cell determines the response to 1O2.

cell biology↗

bioRxiv2021

Recruitment of an ancient branching program to suppress carpel development in maize flowers

Floral morphology is immensely diverse. One developmental process acting to shape this diversity is growth suppression. For example, grass flowers exhibit extreme diversity in floral sexuality, arising through differential suppression of stamens or carpels. In maize, carpels undergo programmed cell death in half of the flowers initiated in ears and in all flowers in tassels. The HD-ZIP I transcription factor gene GRASSY TILLERS1 (GT1) is one of only a few genes known to regulate this process. To identify additional regulators of carpel suppression, we performed a gt1 enhancer screen, and found a genetic interaction between gt1 and ramosa3 (ra3). RA3 is a classic inflorescence meristem determinacy gene that encodes a trehalose-6-phosphate (T6P) phosphatase (TPP). Dissection of floral development revealed that ra3 single mutants have partially derepressed carpels, whereas gt1; ra3 double mutants have completely derepressed carpels. Surprisingly, gt1 suppresses ra3 inflorescence branching, revealing a role for gt1 in meristem determinacy. Supporting these genetic interactions, GT1 and RA3 proteins colocalize to carpel nuclei in developing flowers. Global expression profiling revealed common genes misregulated in single and double mutant flowers, as well as in derepressed gt1 axillary meristems. Indeed, we found that ra3 enhances gt1 vegetative branching, similar to the roles for the trehalose pathway and GT1 homologs in the eudicots. This functional conservation over ~160 million years of evolution reveals ancient roles for GT1-like genes and the trehalose pathway in regulating axillary meristem suppression, later recruited to mediate carpel suppression. Our findings expose hidden pleiotropy of classic maize genes, and show how an ancient developmental program was redeployed to sculpt floral form.

plant biology↗

bioRxiv2020

A partial C4 photosynthetic biochemical pathway in rice

Introduction of a C4 photosynthetic pathway into C3 rice (Oryza sativa) requires installation of a biochemical pump that concentrates CO2 at the site of carboxylation in modified bundle sheath cells. To investigate the feasibility of this, we generated a quadruple line that simultaneously expresses four of the core C4 photosynthetic enzymes from the NADP-malic enzyme subtype, phosphoenolpyruvate carboxylase (ZmPEPC), NADP-malate dehydrogenase (ZmNADP-MDH), NADP-malic enzyme (ZmNADP-ME) and pyruvate phosphate dikinase (ZmPPDK), in a cell-specific manner. This led to enhanced enzyme activity but was largely neutral in its effects on photosynthetic rate and growth. Measurements of the flux of 13CO2 through photosynthetic metabolism revealed a significant increase in the incorporation of 13C into malate, consistent with increased fixation of 13CO2 via PEP carboxylase in lines expressing the maize PEPC enzyme. We also showed 13C labelling of aspartate indicating additional 13CO2 fixation into oxaloacetate by PEPC and conversion to aspartate by the endogenous aspartate aminotransferase activity. However, there were no significant differences in labelling of 3-phosphoglycerate (3PGA) or phosphoenolpyruvate (PEP) indicating limited carbon flux through C4 enzymes into the Calvin-Benson cycle. Crossing the quadruple line with a line with reduced glycine decarboxylase H-protein (OsGDCH) abundance led to a photosynthetic phenotype characteristic of the reduced OsGDCH line and higher labelling of malate, aspartate and citrate. While Kranz anatomy or other anatomical modifications have not yet been installed in these plants to enable a fully functional C4 cycle, these results demonstrate for the first-time flux through the carboxylation phase of C4 metabolism in transgenic rice containing the key metabolic steps in the C4 pathway.

plant biology↗

bioRxiv2019

Proteomic and metabolomic profiling underlines the stage- and time-dependent effects of high temperature on grape berry metabolism

Climate change scenarios predict an increase in mean air temperatures and in the frequency, intensity, and length of extreme temperature events in many wine-growing regions worldwide. Because elevated temperature has detrimental effects on the berry growth and composition, it threatens the economic and environmental sustainability of wine production. Using Cabernet Sauvignon fruit-bearing cuttings, we investigated the effects of high temperature (HT) on grapevine berries through a label-free shotgun proteomic analysis coupled to a complementary metabolomic study. Among the 2279 proteins identified, 592 differentially abundant proteins were found in berries exposed to HT. The gene ontology categories \"Stress\", \"Protein\", \"Secondary metabolism\" and \"Cell wall\" were predominantly altered under HT. High temperatures strongly impaired carbohydrate and energy metabolism, and the effects depended on the stage of development and duration of treatment. Transcript amounts correlated poorly with protein expression levels in HT berries, highlighting the value of proteomic studies in the context of heat stress. Furthermore, this work reveals that HT alters key proteins driving berry development and ripening. Finally, we provide a list of differentially abundant proteins that can be considered as potential markers for developing or selecting grape varieties that are better adapted to warmer climates or extreme heat waves.

plant biology↗

bioRxiv2019

Trehalose 6-phosphate Controls Seed Filling by Inducing Auxin Biosynthesis

Plants undergo several developmental transitions during their life cycle. One of these, the differentiation of the young embryo from a meristem-like structure into a highly-specialized storage organ, is vital to the formation of a viable seed. For crops in which the seed itself is the end product, effective accumulation of storage compounds is of economic relevance, defining the quantity and nutritive value of the harvest yield. However, the regulatory networks underpinning the phase transition into seed filling are poorly understood. Here we show that trehalose 6-phosphate (T6P), which functions as a signal for sucrose availability in plants, mediates seed filling processes in seeds of the garden pea (Pisum sativum), a key grain legume. Seeds deficient in T6P are compromised in size and starch production, resembling the wrinkled seeds studied by Gregor Mendel. We show also that T6P exerts these effects by stimulating the biosynthesis of the pivotal plant hormone, auxin. We found that T6P promotes the expression of the auxin biosynthesis gene TRYPTOPHAN AMINOTRANSFERASE RELATED2 (TAR2), and the resulting effect on auxin levels is required to mediate the T6P-induced activation of storage processes. Our results suggest that auxin acts downstream of T6P to facilitate seed filling, thereby providing a salient example of how a metabolic signal governs the hormonal control of an integral phase transition in a crop plant.

plant biology↗