Thioredoxin f1 and NADPH-dependent thioredoxin reductase C have overlapping functions in regulating photosynthetic metabolism and plant growth in response to varying light conditions

Two different thiol-redox-systems exist in plant chloroplasts, the ferredoxin-thioredoxin system, which depends of ferredoxin reduced by the photosynthetic electron-transport chain and, thus, of light, and the NADPH-dependent thioredoxin reductase C (NTRC) system, which relies on NADPH and thus may be linked to sugar metabolism in the dark. Previous studies suggested therefore that the two different systems may have different functions in plants. We now report that there is a previously unrecognized functional redundancy of thioredoxin-f1 and NTRC in regulating photosynthetic metabolism and growth. In Arabidopsis mutants, combined - but not single - deficiencies of thioredoxin-f1 and NTRC led to severe growth inhibition and perturbed light acclimation, accompanied by strong impairments of Calvin-Benson-cycle activity and starch accumulation. Light-activation of key-enzymes of these pathways, fructose-1,6-bisphosphatase and ADP-glucose pyrophosphorylase, was almost completely abolished. The subsequent increase in NADPH/NADP+ and ATP/ADP ratios led to increased nitrogen assimilation, NADP-malate dehydrogenase activation and light-vulnerability of photosystem I core-proteins. In an additional approach, reporter studies show that Trx f1 and NTRC proteins are both co-localized in the same chloroplast substructure. Results provide genetic evidence that light and NADPH dependent thiol-redox systems interact at the level of thioredoxin-f1 and NTRC to coordinately participate in the regulation of Calvin-Benson-cycle, starch metabolism and growth in response to varying light conditions

Thioredoxin f1 and NADPH-dependent thioredoxin reductase C have overlapping functions in regulating photosynthetic metabolism and plant growth in response to varying light conditions

Two different thiol-redox-systems exist in plant chloroplasts, the ferredoxin-thioredoxin system, which depends of ferredoxin reduced by the photosynthetic electron-transport chain and, thus, of light, and the NADPH-dependent thioredoxin reductase C (NTRC) system, which relies on NADPH and thus may be linked to sugar metabolism in the dark. Previous studies suggested therefore that the two different systems may have different functions in plants. We now report that there is a previously unrecognized functional redundancy of thioredoxin-f1 and NTRC in regulating photosynthetic metabolism and growth. In Arabidopsis mutants, combined - but not single - deficiencies of thioredoxin-f1 and NTRC led to severe growth inhibition and perturbed light acclimation, accompanied by strong impairments of Calvin-Benson-cycle activity and starch accumulation. Light-activation of key-enzymes of these pathways, fructose-1,6-bisphosphatase and ADP-glucose pyrophosphorylase, was almost completely abolished. The subsequent increase in NADPH/NADP+ and ATP/ADP ratios led to increased nitrogen assimilation, NADP-malate dehydrogenase activation and light-vulnerability of photosystem I core-proteins. In an additional approach, reporter studies show that Trx f1 and NTRC proteins are both co-localized in the same chloroplast substructure. Results provide genetic evidence that light and NADPH dependent thiol-redox systems interact at the level of thioredoxin-f1 and NTRC to coordinately participate in the regulation of Calvin-Benson-cycle, starch metabolism and growth in response to varying light conditions.Peer reviewe

Metabolic alterations triggered by silicon nutrition is there a signaling role for silicon?

Although the beneficial role of silicon (Si) in stimulating the growth and development of many plants is generally accepted, our knowledge concerning the physiological and molecular mechanisms underlying this response remains far from comprehensive. Considerable effort has been invested in understanding the role of Si on plant disease, which has led to several new and compelling hypotheses; in unstressed plants, however, Si is believed to have no molecular or metabolic effects. Recently, we have demonstrated that Si nutrition can modulate the carbon/nitrogen balance in unstressed rice plants. Our findings point to an important role of Si as a signaling metabolite able to promote amino acid remobilization. In this article we additionally discuss the agronomic significance of these novel observations and suggest Si nutrition as an important target in future attempts to improve yields of agronomic crops

Trehalose 6-phosphate promotes seed filling by activating 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 believed to be controlled by local connections between sugars and hormonal response systems. However, we know little about the regulatory networks underpinning the sugar–hormone interactions in developing seeds. By modulating the trehalose 6-phosphate (T6P) content in growing embryos of garden pea (Pisum sativum), we investigate here the role of this signaling sugar during the seed-filling process. 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 concentrations 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

Good things come to those who wait - a 42-yr study challenges 'trade-off' theories

This article is a Commentary on Chen et al. (2024), 241: 623–631

Von der Revolution in der DDR zur deutschen Einheit: Auswahlbibliographie ; 1989 - 1990

Available from Bibliothek des Instituts fuer Weltwirtschaft, ZBW, Duesternbrook Weg 120, D-24105 Kiel C 171495 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Signaling pathways in legume seed development : evidence for a crosstalk between trehalose 6-phosphate and auxin ; [kumulative Dissertation]

Samen bestimmen die Fortpflanzungsfähigkeit von Pflanzen und sind für ihre Existenz lebenswichtig. Unabhängig von ihrer biologischen Bedeutung sind Ertrag und Qualität des Saatguts für die moderne Pflanzenzüchtung und die effiziente Lebensmittelproduktion von erheblichem Interesse. Die molekularen Mechanismen, die die Samengröße und die Akkumulation von Speicherverbindungen regulieren, sind jedoch immer noch nicht gut geklärt. Anhand verschiedener Leguminosenmodelle mit großen Samen wird nun gezeigt, dass sowohl die Samenfüllung als auch die Samengröße von der transkriptionellen Aktivierung der Auxinbiosynthese durch den Signalzuckertrehalose-6-phosphat (T6P) abhängen. Die Feststellung, dass T6P stromaufwärts von Auxin wirkt, ist ein herausragendes Beispiel dafür, wie ein metabolisches Signal die hormonelle Kontrolle einer integralen Entwicklungsphase in Pflanzen steuert.Seeds determine the reproductive capacity of plants and are vital to their existence. Regardless of their biological importance, yield and quality of seeds are of significant interest for modern plant breeding and efficient food production. However, the molecular mechanisms regulating seed size and storage compound accumulation are still not well elucidated. Taking advantage of different large-seeded legume models, it is now shown that both seed filling and seed size are dependent on the transcriptional activation of auxin biosynthesis by the signaling sugar trehalose 6-phosphate (T6P). The finding that T6P acts upstream of auxin provides a salient example of how a metabolic signal governs the hormonal control of an integral developmental phase in plants

Hybrid embryos of Vicia faba develop enhanced sink strength, which is established during early development

P>Selfed and crossed seeds of two homozygous Vicia faba lines served as models for the analysis of the physiological and molecular mechanisms underlying embryo heterosis. Profiles of transcripts, metabolites and seed contents of developing embryos were analysed to compare the means of reciprocally crossed and selfed seeds growing on the same mother plants. The mean weight of mature hybrid seeds was demonstrably higher, revealing mid-parent heterosis. Hybrid embryos exhibited a prolonged early phase of development and delayed onset of storage activity. Accordingly, transcript profiling indicates stimulation of cell proliferation, an effect, which is potentially mediated by activation of auxin functions within a framework of growth-related transcription factors. At the transcript level, activated cell proliferation increased assimilate uptake activity and thereby seed sink strength. This situation might finally lead to the increased size of the hybrid seeds. We conclude that hybrid seeds are characterised by accelerated growth during early development, which increases storage capacity and leads to higher metabolic fluxes. These needs are, at least partially, met by increased assimilate uptake capacity. The stimulated growth of hybrid seeds shifted metabolite profiles and potentially depleted available pools. Such metabolic shifts are most likely secondary effects resulting from the higher storage capacity of hybrid seeds, a heterotic feature, which is itself established very early in seed development.Deutsche Forschungsgemeinschaft [LI 586/5-3, WE 1641/10-3