Authors: Elodie Parre Anja Geitmann
Publish Date: 2004/09/21
Volume: 220, Issue: 4, Pages: 582-592
Abstract
The cell wall is one of the structural key players regulating pollen tube growth since plant cell expansion depends on an interplay between intracellular driving forces and the controlled yielding of the cell wall Pectin is the main cell wall component at the growing pollen tube apex We therefore assessed its role in pollen tube growth and cytomechanics using the enzymes pectinase and pectin methyl esterase PME Pectinase activity was able to stimulate pollen germination and tube growth at moderate concentrations whereas higher concentrations caused apical swelling or bursting in Solanum chacoense Bitt pollen tubes This is consistent with a modification of the physical properties of the cell wall affecting its extensibility and thus the growth rate as well as its capacity to withstand turgor To prove that the enzymeinduced effects were due to the altered cell wall mechanics we subjected pollen tubes to microindentation experiments We observed that cellular stiffness was reduced and viscoelasticity increased in the presence of pectinase These are the first mechanical data that confirm the influence of the amount of pectins in the pollen tube cell wall on the physical parameters characterizing overall cellular architecture Cytomechanical data were also obtained to analyze the role of the degree of pectin methylesterification which is known to exhibit a gradient along the pollen tube axis This feature has frequently been suggested to result in a gradient of the physical properties characterizing the cell wall and our data provide for the first time mechanical support for this concept The gradient in cell wall composition from apical esterified to distal deesterified pectins seems to be correlated with an increase in the degree of cell wall rigidity and a decrease of viscoelasticity Our mechanical approach provides new insights concerning the mechanics of pollen tube growth and the architecture of living plant cellsThis research was supported by grants from the Natural Sciences and Engineering Research Council of Canada NSERC the Canadian Foundation for Innovation CFI and the Fonds Québecois de la Recherche sur la Nature et les Technologies FQRNT to A Geitmann The generous gifts of monoclonal antibodies JIM5 and JIM7 from Keith Roberts John Innes Centre Norwich UK and from Paul Knox Leeds University UK are gratefully acknowledged We also thank William B McConnaughey Washington University St Louis Missouri for assistance with the microindentation setup
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