Figure 1.

Changes in the Primary Cell Wall under Water-Deficit Stress.

(A) Cell wall structure. The primary cell wall mainly consists of cellulose microfibrils, xyloglucan, and pectin. The orientation of cellulose microfibrils is largely determined by microtubule arrays. The current model suggests that xyloglucans localize to cellulose bundles, while pectins form a network that coats the cellulose. Cross-linked pectins that tether cellulose microfibrils may be load-bearing. Blue arrows indicate turgor pressure.

(B) Changes in cell wall properties under water-deficit stress. Under water-deficit stress, the cell wall deforms and dissociates from the plasma membrane. Cellulose biosynthesis is disrupted due to the depolymerization of microtubules under these conditions. Different stresses may trigger unique changes in addition to the general effect caused by water loss by the cell. For example, sodium ions (Na⁺) may disrupt pectin cross-links as well as microtubule arrays. Changes in cell wall integrity may be monitored directly by RLKs or indirectly by membrane-localized mechanosensitive channels.

(C) Comparison of cells under standard and salt stress conditions. With plasmolysis, most of the cell membrane dissociates from the cell wall. The cellulose synthase complex dislocates from the cell membrane as the microtubules depolymerize. CC1/2 proteins remain associated with the CSCs and aid the reassembly of the microtubule array and relocalization of CSCs under salt stress.