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243 results on '"Zeeman, Samuel C."'

4. Morphological bases of phytoplankton energy management and physiological responses unveiled by 3D subcellular imaging

Author

Uwizeye, Clarisse, Decelle, Johan, Jouneau, Pierre-Henri, Flori, Serena, Gallet, Benoit, Keck, Jean-Baptiste, Bo, Davide Dal, Moriscot, Christine, Seydoux, Claire, Chevalier, Fabien, Schieber, Nicole L., Templin, Rachel, Allorent, Guillaume, Courtois, Florence, Curien, Gilles, Schwab, Yannick, Schoehn, Guy, Zeeman, Samuel C., Falconet, Denis, and Finazzi, Giovanni

Published
2021
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8. MFP1 defines the subchloroplast location of starch granule initiation.

Author

Sharma, Mayank, Abt, Melanie R., Eicke, Simona, Ilse, Theresa E., Chun Liu, Lucas, Miriam S., Pfister, Barbara, and Zeeman, Samuel C.

Subjects
STARCH, RICE starch, RICE products, CHLOROPLASTS, CARBOHYDRATES
Abstract

Starch is one of the major carbohydrate storage compounds in plants. The biogenesis of starch granules starts with the formation of initials, which subsequently expand into granules. Several coiled-coil domain-containing proteins have been previously implicated with the initiation process, but the mechanisms by which they act remain largely elusive. Here, we demonstrate that one of these proteins, the thylakoid-associated MAR-BINDING FILAMENT-LIKE PROTEIN 1 (MFP1), specifically determines the subchloroplast location of initial formation. The expression of MFP1 variants "mis"-targeted to specific locations within chloroplasts in Arabidopsis results in distinctive shifts in not only how many but also where starch granules are formed. Importantly, "re" localizing MFP1 to the stromal face of the chloroplast's inner envelope is sufficient to generate starch granules in this aberrant position. These findings provide compelling evidence that a single protein MFP1 possesses the capacity to direct the initiation and biosynthesis machinery of starch granules. [ABSTRACT FROM AUTHOR]

Published
2024
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9. Plasmodesmal connectivity in C4Gynandropsis gynandra is induced by light and dependent on photosynthesis.

Author

Schreier, Tina B., Müller, Karin H., Eicke, Simona, Faulkner, Christine, Zeeman, Samuel C., and Hibberd, Julian M.

Subjects
CARBON 4 photosynthesis, PLASMODESMATA, PHOTOSYNTHESIS, DICOTYLEDONS, INHIBITORY postsynaptic potential, FOLIAGE plants, DECARBOXYLATION
Abstract

Summary: In leaves of C4 plants, the reactions of photosynthesis become restricted between two compartments. Typically, this allows accumulation of C4 acids in mesophyll (M) cells and subsequent decarboxylation in the bundle sheath (BS). In C4 grasses, proliferation of plasmodesmata between these cell types is thought to increase cell‐to‐cell connectivity to allow efficient metabolite movement. However, it is not known whether C4 dicotyledons also show this enhanced plasmodesmal connectivity and so whether this is a general requirement for C4 photosynthesis is not clear. How M and BS cells in C4 leaves become highly connected is also not known.We investigated these questions using 3D‐ and 2D‐electron microscopy on the C4 dicotyledon Gynandropsis gynandra as well as phylogenetically close C3 relatives.The M–BS interface of C4G. gynandra showed higher plasmodesmal frequency compared with closely related C3 species. Formation of these plasmodesmata was induced by light. Pharmacological agents that perturbed photosynthesis reduced the number of plasmodesmata, but this inhibitory effect could be reversed by the provision of exogenous sucrose.We conclude that enhanced formation of plasmodesmata between M and BS cells is wired to the induction of photosynthesis in C4G. gynandra. [ABSTRACT FROM AUTHOR]

Published
2024
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27. Fluid flow structures gut microbiota biofilm communities by distributing public goods.

Author

Wong, Jeremy P. H., Flscher-Stettler, Michaela, Zeeman, Samuel C., Battin, Tom J., and Persat, Alexandre

Subjects
MICROBIAL communities, PUBLIC goods, FLUID flow, GUT microbiome, COMMON good
Abstract

Bacterial gut commensals experience a biologically and physically complex mucosal environment. While many chemical factors mediate the composition and structure of these microbial communities, less is known about the role of mechanics. Here, we demonstrate that fluid flow impacts the spatial organization and composition of gut biofilm communities by shaping how different species interact metabolically. We first demonstrate that a model community composed of Bacteroides thetaiotaomicron (Bt) and Bacteroides fragilis (Bf), two representative human commensals, can form robust biofilms in flow. We identified dextran as a polysaccharide readily metabolized by Bt but not Bf, but whose fermentation generates a public good enabling Bf growth. By combining simulations with experiments, we demonstrate that in flow, Bt biofilms share dextran metabolic by-products, promoting Bf biofilm formation. By transporting this public good, flow structures the spatial organization of the community, positioning the Bf population downstream from Bt. We show that sufficiently strong flows abolish Bf biofilm formation by limiting the effective public good concentration at the surface. Physical factors such as flow may therefore contribute to the composition of intestinal microbial communities, potentially impacting host health. [ABSTRACT FROM AUTHOR]

Published
2023
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28. Effective root responses to salinity stress include maintained cell expansion and carbon allocation.

Author

Li, Hongfei, Duijts, Kilian, Pasini, Carlo, van Santen, Joyce E., Lamers, Jasper, de Zeeuw, Thijs, Verstappen, Francel, Wang, Nan, Zeeman, Samuel C., Santelia, Diana, Zhang, Yanxia, and Testerink, Christa

Subjects
ROOT growth, SALT tolerance in plants, SALINITY, GENE regulatory networks, ABSCISIC acid, ARABIDOPSIS thaliana
Abstract

Summary: Acclimation of root growth is vital for plants to survive salt stress. Halophytes are great examples of plants that thrive even under severe salinity, but their salt tolerance mechanisms, especially those mediated by root responses, are still largely unknown.We compared root growth responses of the halophyte Schrenkiella parvula with its glycophytic relative species Arabidopsis thaliana under salt stress and performed transcriptomic analysis of S. parvula roots to identify possible gene regulatory networks underlying their physiological responses.Schrenkiella parvula roots do not avoid salt and experience less growth inhibition under salt stress. Salt‐induced abscisic acid levels were higher in S. parvula roots compared with Arabidopsis. Root transcriptomic analysis of S. parvula revealed the induction of sugar transporters and genes regulating cell expansion and suberization under salt stress. 14C‐labeled carbon partitioning analyses showed that S. parvula continued allocating carbon to roots from shoots under salt stress while carbon barely allocated to Arabidopsis roots. Further physiological investigation revealed that S. parvula roots maintained root cell expansion and enhanced suberization under severe salt stress.In summary, roots of S. parvula deploy multiple physiological and developmental adjustments under salt stress to maintain growth, providing new avenues to improve salt tolerance of plants using root‐specific strategies. [ABSTRACT FROM AUTHOR]

Published
2023
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