Demethylesterification of Cell Wall Pectins in Arabidopsis Plays a Role in Seed Germination

Muller, Kerstin and Levesque-Tremblay, Gabriel and Bartels, Sebastian and Weitbrecht, Karin and Wormit, Alexandra and Usadel, Bjoern and Haughn, George and Kermode, Allison R.. (2013) Demethylesterification of Cell Wall Pectins in Arabidopsis Plays a Role in Seed Germination. Plant physiology, Vol. 161, H. 1. pp. 305-316.

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Official URL: http://edoc.unibas.ch/dok/A6083331

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The methylesterification status of cell wall homogalacturonans, mediated through the action of pectin methylesterases (PMEs), influences the biophysical properties of plant cell walls such as elasticity and porosity, important parameters for cell elongation and water uptake. The completion of seed germination requires cell wall extensibility changes in both the radicle itself and in the micropylar tissues surrounding the radicle. In wild-type seeds of Arabidopsis (Arabidopsis thaliana), PME activities peaked around the time of testa rupture but declined just before the completion of germination (endosperm weakening and rupture). We overexpressed an Arabidopsis PME inhibitor to investigate PME involvement in seed germination. Seeds of the resultant lines showed a denser methylesterification status of their cell wall homogalacturonans, but there were no changes in the neutral sugar and uronic acid composition of the cell walls. As compared with wild-type seeds, the PME activities of the overexpressing lines were greatly reduced throughout germination, and the low steady-state levels neither increased nor decreased. The most striking phenotype was a significantly faster rate of germination, which was not connected to altered testa rupture morphology but to alterations of the micropylar endosperm cells, evident by environmental scanning electron microscopy. The transgenic seeds also exhibited an apparent reduced sensitivity to abscisic acid with respect to its inhibitory effects on germination. We speculate that PME activity contributes to the temporal regulation of radicle emergence in endospermic seeds by altering the mechanical properties of the cell walls and thereby the balance between the two opposing forces of radicle elongation and mechanical resistance of the endosperm.
Faculties and Departments:05 Faculty of Science > Departement Umweltwissenschaften > Ehemalige Einheiten Umweltwissenschaften > Pflanzenphysiologie Pathogenabwehr (Boller)
UniBasel Contributors:Merker, Sebastian
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:American Society of Plant Biologists
Note:Publication type according to Uni Basel Research Database: Journal article
Identification Number:
Last Modified:24 May 2013 09:22
Deposited On:24 May 2013 09:04

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