Journal: Plant Physiology

Abbreviation

Plant physiol.

Publisher

Oxford University Press

Journal Volumes

ISSN

0032-0889
1532-2548

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2021 - 202516
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Publications 1 - 10 of 16
  • Asymmetric expression of Argonautes in reproductive tissues
    Item type: Other Journal Item
    Jullien, Pauline E.; Schröder, Jens; Bonnet, Diane M.V.; et al. (2022)
    Plant Physiology
  • A point mutation in the photosystem II protein PsbW disrupts thylakoid organization and alters starch granule formation
    Item type: Journal Article
    Ilse, Theresa E.; Zhang, Hongyuan; Heutinck, Arvid; et al. (2025)
    Plant Physiology
    Chloroplast thylakoid membranes are the sites of the light reactions of photosynthesis. They are also thought to influence starch granule biogenesis via the thylakoid-anchored protein MAR-BINDING FILAMENT-LIKE PROTEIN 1 (MFP1), but mechanistic understanding is scarce. Here, we report an Arabidopsis (Arabidopsis thaliana) mutant affected in PHOTOSYSTEM II REACTION CENTER W (PsbW), an integral thylakoid membrane protein associated with photosynthetic complexes of PSII. This mutant (psbw-2) was identified in a large-scale mutant screen designed to find proteins that regulate starch granule shape and size because it produces an excessive number of small, irregularly-shaped starch granules. The mutation in psbw-2 causes a glycine-to-arginine substitution in PsbW's transmembrane helix. The resulting PsbW$^{G107R}$ protein remains membrane-associated but has lost its ability to stabilize PSII supercomplexes. In addition, the transgenic expression of this mutated version results in abnormal thylakoid membranes that have drastically enlarged luminal spaces and no longer-form distinct grana stacks, leading to reduced plant growth and impaired photosynthesis. These effects increase with PsbW$^{G107R}$ expression levels but are not observed in the psbw knockout mutant, suggesting that PsbW$^{G107R}$ has acquired an aberrant function. We analyzed psbw-2 mutants also lacking either MFP1 or STARCH SYNTHASE 4 (SS4), a key factor involved in granule initiation and growth. These data suggest that thylakoid distortion is caused by the membrane insertion of PsbW$^{G107R}$, which in turn affects the initiation and growth of starch granules. Our results reaffirm the link between the thylakoid membrane system and starch formation and highlight the importance of proper thylakoid architecture for plant fitness.
  • Soluble and insoluble α-glucan synthesis in yeast by enzyme suites derived exclusively from maize endosperm
    Item type: Journal Article
    Boehlein, Susan K.; Pfister, Barbara; Hennen-Bierwagen, Tracie A.; et al. (2023)
    Plant Physiology
    Molecular mechanisms that distinguish the synthesis of semi-crystalline & alpha;-glucan polymers found in plant starch granules from the synthesis of water-soluble polymers by nonplant species are not well understood. To address this, starch biosynthetic enzymes from maize (Zea mays L.) endosperm were isolated in a reconstituted environment using yeast (Saccharomyces cerevisiae) as a test bed. Ninety strains were constructed containing unique combinations of 11 synthetic transcription units specifying maize starch synthase (SS), starch phosphorylase (PHO), starch branching enzyme (SBE), or isoamylase-type starch debranching enzyme (ISA). Soluble and insoluble branched & alpha;-glucans accumulated in varying proportions depending on the enzyme suite, with ISA function stimulating distribution into the insoluble form. Among the SS isoforms, SSIIa, SSIII, and SSIV individually supported the accumulation of glucan polymer. Neither SSI nor SSV alone produced polymers; however, synergistic effects demonstrated that both isoforms can stimulate & alpha;-glucan accumulation. PHO did not support & alpha;-glucan production by itself, but it had either positive or negative effects on polymer content depending on which SS or a combination thereof was present. The complete suite of maize enzymes generated insoluble particles resembling native starch granules in size, shape, and crystallinity. Ultrastructural analysis revealed a hierarchical assembly starting with subparticles of approximately 50 nm diameter that coalesce into discrete structures of approximately 200 nm diameter. These are assembled into semi-crystalline & alpha;-glucan superstructures up to 4 & mu;m in length filling most of the yeast cytosol. ISA was not essential for the formation of such particles, but their abundance was increased dramatically by ISA presence.
  • Abscisic acid modulates neighbor proximity-induced leaf hyponasty in Arabidopsis
    Item type: Journal Article
    Michaud, Olivier; Krahmer, Johanna; Galbier, Florian; et al. (2023)
    Plant Physiology
    Leaves of shade-avoiding plants such as Arabidopsis (Arabidopsis thaliana) change their growth pattern and position in response to low red to far-red ratios (LRFRs) encountered in dense plant communities. Under LRFR, transcription factors of the phytochrome-interacting factor (PIF) family are derepressed. PIFs induce auxin production, which is required for promoting leaf hyponasty, thereby favoring access to unfiltered sunlight. Abscisic acid (ABA) has also been implicated in the control of leaf hyponasty, with gene expression patterns suggesting that LRFR regulates the ABA response. Here, we show that LRFR leads to a rapid increase in ABA levels in leaves. Changes in ABA levels depend on PIFs, which regulate the expression of genes encoding isoforms of the enzyme catalyzing a rate-limiting step in ABA biosynthesis. Interestingly, ABA biosynthesis and signaling mutants have more erect leaves than wild-type Arabidopsis under white light but respond less to LRFR. Consistent with this, ABA application decreases leaf angle under white light; however, this response is inhibited under LRFR. Tissue-specific interference with ABA signaling indicates that an ABA response is required in different cell types for LRFR-induced hyponasty. Collectively, our data indicate that LRFR triggers rapid PIF-mediated ABA production. ABA plays a different role in controlling hyponasty under white light than under LRFR. Moreover, ABA exerts its activity in multiple cell types to control leaf position.
  • LIKE EARLY STARVATION 1 interacts with amylopectin during starch biosynthesis
    Item type: Journal Article
    Osman, Rayan; Bossu, Mélanie; Dauvillée, David; et al. (2024)
    Plant Physiology
    Starch is the major energy storage compound in plants. Both transient starch and long-lasting storage starch accumulate in the form of insoluble, partly crystalline granules. The structure of these granules is related to the structure of the branched polymer amylopectin: linear chains of glucose units organized in double helices that align to form semicrystalline lamellae, with branching points located in amorphous regions between them. EARLY STARVATION 1 (ESV1) and LIKE EARLY STARVATION 1 (LESV) proteins are involved in the maintenance of starch granule structure and in the phase transition of amylopectin, respectively, in Arabidopsis (Arabidopsis thaliana). These proteins contain a conserved tryptophan-rich C-terminal domain folded into an antiparallel beta-sheet, likely responsible for binding of the proteins to starch, and different N-terminal domains whose structure and function are unknown. In this work, we combined biochemical and biophysical approaches to analyze the structures of LESV and ESV1 and their interactions with the different starch polyglucans. We determined that both proteins interact with amylopectin but not with amylose and that only LESV is capable of interacting with amylopectin during starch biosynthesis. While the C-terminal domain interacts with amylopectin in its semicrystalline form, the N-terminal domain of LESV undergoes induced conformational changes that are probably involved in its specific function of mediating glucan phase transition. These results clarify the specific mechanism of action of these 2 proteins in the biosynthesis of starch granules.
  • Starch metabolism in guard cells: At the intersection of environmental stimuli and stomatal movement
    Item type: Review Article
    Dang, Trang; Piro, Lucia; Pasini, Carlo; et al. (2024)
    Plant Physiology
    Starch metabolism in guard cells plays a central role in regulating stomatal movement in response to light, elevated ambient CO₂ and potentially other abiotic and biotic factors. Here, we discuss how various guard cell signal transduction pathways converge to promote rearrangements in guard cell starch metabolism for efficient stomatal responses, an essential physiological process that sustains plant productivity and stress tolerance. We suggest manipulation of guard cell starch dynamics as a previously overlooked strategy to improve stomatal behavior under changing environmental conditions.
  • Temporal and spatial frameworks supporting plant responses to vegetation proximity
    Item type: Journal Article
    Pastor-Andreu, Pedro; Moreno-Romero, Jordi; Urdin-Bravo, Mikel; et al. (2024)
    Plant Physiology
    After the perception of vegetation proximity by phytochrome photoreceptors, shade-avoider plants initiate a set of responses known as the shade avoidance syndrome (SAS). Shade perception by the phytochrome B (phyB) photoreceptor unleashes the PHYTOCHROME INTERACTING FACTORs and initiates SAS responses. In Arabidopsis (Arabidopsis thaliana) seedlings, shade perception involves rapid and massive changes in gene expression, increases auxin production, and promotes hypocotyl elongation. Other components, such as phyA and ELONGATED HYPOCOTYL 5, also participate in the shade regulation of the hypocotyl elongation response by repressing it. However, why and how so many regulators with either positive or negative activities modulate the same response remains unclear. Our physiological, genetic, cellular, and transcriptomic analyses showed that (i) these components are organized into 2 main branches or modules and (ii) the connection between them is dynamic and changes with the time of shade exposure. We propose a model for the regulation of shade-induced hypocotyl elongation in which the temporal and spatial functional importance of the various SAS regulators analyzed here helps to explain the coexistence of differentiated regulatory branches with overlapping activities.
  • Starch biosynthesis in guard cells has features of both autotrophic and heterotrophic tissues
    Item type: Journal Article
    Flütsch, Sabrina; Horrer, Daniel; Santelia, Diana (2022)
    Plant Physiology
    The pathway of starch synthesis in guard cells (GCs), despite the crucial role starch plays in stomatal movements, is not well understood. Here, we characterized starch dynamics in GCs of Arabidopsis (Arabidopsis thaliana) mutants lacking enzymes of the phosphoglucose isomerase-phosphoglucose mutase-ADP-glucose pyrophosphorylase starch synthesis pathway in leaf mesophyll chloroplasts or sugar transporters at the plastid membrane, such as glucose-6-phosphate/phosphate translocators, which are active in heterotrophic tissues. We demonstrate that GCs have metabolic features of both photo-autotrophic and heterotrophic cells. GCs make starch using different carbon precursors depending on the time of day, which can originate both from GC photosynthesis and/or sugars imported from the leaf mesophyll. Furthermore, we unravel the major enzymes involved in GC starch synthesis and demonstrate that they act in a temporal manner according to the fluctuations of stomatal aperture, which is unique for GCs. Our work substantially enhances our knowledge on GC starch metabolism and uncovers targets for manipulating GC starch dynamics to improve stomatal behavior, directly affecting plant productivity.
  • The impact of drought-induced root and root hair shrinkage on root-soil contact
    Item type: Other Journal Item
    Duddek, Patrick; Carminati, Andrea; Koebernick, Nicolai; et al. (2022)
    Plant Physiology
    Although root hairs significantly increased root-soil contact, in maize, their shrinkage during soil drying is initiated at relatively high soil matric potentials (between -10 and -310 kPa).
  • Chronic warming and dry soils limit carbon uptake and growth despite a longer growing season in beech and oak
    Item type: Journal Article
    Didion-Gency, Margaux; Vitasse, Yann; Buchmann, Nina; et al. (2024)
    Plant Physiology
    Progressively warmer and drier climatic conditions impact tree phenology and carbon cycling with large consequences for forest carbon balance. However, it remains unclear how individual impacts of warming and drier soils differ from their combined effects and how species interactions modulate tree responses. Using mesocosms, we assessed the multiyear impact of continuous air warming and lower soil moisture alone or in combination on phenology, leaf-level photosynthesis, nonstructural carbohydrate concentrations, and aboveground growth of young European beech (Fagus sylvatica L.) and Downy oak (Quercus pubescens Willd.) trees. We further tested how species interactions (in monocultures and in mixtures) modulated these effects. Warming prolonged the growing season of both species but reduced growth in oak. In contrast, lower moisture did not impact phenology but reduced carbon assimilation and growth in both species. Combined impacts of warming and drier soils did not differ from their single effects. Under warmer and drier conditions, performances of both species were enhanced in mixtures compared to monocultures. Our work revealed that higher temperature and lower soil moisture have contrasting impacts on phenology vs. leaf-level assimilation and growth, with the former being driven by temperature and the latter by moisture. Furthermore, we showed a compensation in the negative impacts of chronic heat and drought by tree species interactions.
Publications 1 - 10 of 16