The Control of Cell Size and Rate of Elongation in the Arabidopsis Root

Abstract

The control of cell elongation is studied in the root of Arabidopsis by focusing on reduction of cell size. Reduced organ size is a common response of a plant to different exogenous and endogenous signals. There is not a single specific event/actor that is solely responsible for the fast inhibition of cell elongation, but a battery of different actors at different levels work together to result in cell elongation arrest. A reduction of cell wall loosening seems to be achieved by cross-linking of structural proteins, by creating a suboptimal pH-environment for loosening enzymes by modulation of H +-ATPase activity and by structural changes in the composition and architecture of the cell walls. Microtubules and the reorientation of cellulose microfibrils are not involved in the control of cell elongation in the Arabidopsis root. Significant alterations in cellular symplast exchange, brought about by modulation of plasmodesmal transport, certainly influence the cell's general metabolism. In combination with changes that directly influence cell wall properties this may lead to the observed cell elongation arrest in the Arabidopsis root.