title: Cell wall assembly and intracellular trafficking in plant cells are directly affected by changes in the magnitude of gravitational acceleration.
abstract: Plants are able to sense the magnitude and direction of gravity. This capacity is thought to reside in selected cell types within the plant body that are equipped with specialized organelles called statoliths. However, most plant cells do not possess statoliths, yet they respond to changes in gravitational acceleration. To understand the effect of gravity on the metabolism and cellular functioning of non-specialized plant cells, we investigated a rapidly growing plant cell devoid of known statoliths and without gravitropic behavior, the pollen tube. The effects of hyper-gravity and omnidirectional exposure to gravity on intracellular trafficking and on cell wall assembly were assessed in Camellia pollen tubes, a model system with highly reproducible growth behavior in vitro. Using an epi-fluorescence microscope mounted on the Large Diameter Centrifuge at the European Space Agency, we were able to demonstrate that vesicular trafficking is reduced under hyper-gravity conditions. Immuno-cytochemistry confirmed that both in hyper and omnidirectional gravity conditions, the characteristic spatial profiles of cellulose and callose distribution in the pollen tube wall were altered, in accordance with a dose-dependent effect on pollen tube diameter. Our findings suggest that in response to gravity induced stress, the pollen tube responds by modifying cell wall assembly to compensate for the altered mechanical load. The effect was reversible within few minutes demonstrating that the pollen tube is able to quickly adapt to changing stress conditions.
authors.affiliation: Institut de recherche en biologie végétale, Département de sciences biologiques, Université de Montréal, Montréal, Québec, Canada.
authors.forename: Youssef
authors.initials: Y
authors.lastname: Chebli
authors.forename: Lauranne
authors.initials: L
authors.lastname: Pujol
authors.forename: Anahid
authors.initials: A
authors.lastname: Shojaeifard
authors.forename: Iman
authors.initials: I
authors.lastname: Brouwer
authors.forename: Jack J W A
authors.initials: JJ
authors.lastname: van Loon
authors.forename: Anja
authors.initials: A
authors.lastname: Geitmann
mesh_terms: D001692:Biological Transport; D002473:Cell Wall / Q000378:metabolism*; D002482:Cellulose / Q000378:metabolism; D022162:Cytoplasmic Vesicles / Q000378:metabolism; D018525:Germination; D005936:Glucans / Q000378:metabolism; D006112:Gravitation; D042541:Intracellular Space; D059828:Plant Cells / Q000378:metabolism*; D053205:Pollen Tube / Q000166:cytology / Q000254:growth & development / Q000378:metabolism
chemical_list: D005936:Glucans; D002482:Cellulose; C048306:callose