Abstract
How is the extensibility of growing plant cell walls regulated? In the past, most studies have focused on the role of the cellulose/xyloglucan network and the enigmatic wall-loosening agents expansins. Here we review first how in the closest relatives of the land plants, the Charophycean algae, cell wall synthesis is coupled to cell wall extensibility by a chemical Ca2+-exchange mechanism between Ca2+–pectate complexes. We next discuss evidence for the existence in terrestrial plants of a similar “primitive” Ca2+–pectate-based growth control mechanism in parallel to the more recent, land plant-specific, expansin-dependent process.
Highlights
Plant cell growth reflects the balance between the extensibility of the cell wall and the forces exerted on the wall by the turgor pressure
Wall relaxation and cell expansion can occur, in principle, with or without a change in wall strength, depending on whether or not this chemorheological process causes a net change in the number or strength of the load-bearing bonds
The current “textbook view” of the control of cell wall extensibility (Carpita and McCann, 2000) is largely based on a series of seminal extensometer experiments, which showed that acid-promoted wall extension under a constant tension, referred to as creep, can be reproduced on isolated walls
Summary
Plant cell growth reflects the balance between the extensibility of the cell wall and the forces exerted on the wall by the turgor pressure. Wall relaxation and cell expansion can occur, in principle, with or without a change in wall strength, depending on whether or not this chemorheological process causes a net change in the number or strength of the load-bearing bonds.
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