Research Article

Cell wall remodeling and vesicle trafficking mediate the root clock in Arabidopsis

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Science  13 Nov 2020:
Vol. 370, Issue 6518, pp. 819-823
DOI: 10.1126/science.abb7250

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Signaling for a weakness in cell walls

Lateral roots form at regular intervals in the small mustard plant Arabidopsis thaliana. Wachsman et al. have now identified both pectin and subcellular vesicle trafficking as part of the oscillating signaling system that initiates lateral roots. Esterification of pectin regulates its function at the nascent lateral root site, altering the stiffness of cell walls and the strength of cell-cell adhesion. Because lateral root primordia must push through overlying cell layers, reduced cell adhesion at these sites might aid in the formation of lateral roots.

Science, this issue p. 819

Abstract

In Arabidopsis thaliana, lateral roots initiate in a process preceded by periodic gene expression known as the root clock. We identified the vesicle-trafficking regulator GNOM and its suppressor, ADENOSINE PHOSPHATE RIBOSYLATION FACTOR GTPase ACTIVATION PROTEIN DOMAIN3, as root clock regulators. GNOM is required for the proper distribution of pectin, a mediator of intercellular adhesion, whereas the pectin esterification state is essential for a functional root clock. In sites of lateral root primordia emergence, both esterified and de-esterified pectin variants are differentially distributed. Using a reverse-genetics approach, we show that genes controlling pectin esterification regulate the root clock and lateral root initiation. These results indicate that the balance between esterified and de-esterified pectin states is essential for proper root clock function and the subsequent initiation of lateral root primordia.

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