FIGURE 2.

Putative components sensing physical and chemical signals in the plant root cell wall and plasma membrane under salt stress. (A) Cellular distribution of components known to be or that might be involved in salt stress perception; (B) The salt stress sensing process mediated by cell wall and plasma membrane components. The components in the cell wall and cell membrane perceive salt stress. Salt stress causes cell deformation. In the cell wall, the polysaccharides (e.g., cellulose, xyloglucan, and pectin RG-II), phenolic compounds, and proteins (e.g., GRP, glycoproteins, and extensin) undergo conformational changes due to the perception of a certain factor or binding with a certain substance such as Na⁺. Similarly, plasma membrane components such as proteins (e.g., annexin), transporters (e.g., SOS1), channels (e.g., CNGC), kinases (e.g., HPK), and sphingolipids (e.g., GIPC) also cause conformational changes in the cell wall or membrane followed by a series of biochemical reactions due to the sensing of a certain factor or binding with a certain substance such as Na⁺. These receptor-like components can also interact with each other to sense signals. RG-II, Rhamnogalacturonan II; GRP, glycine-rich protein; MSC, mechanosensory channel; CNGC, cyclic nucleotide-gated channel; HPK, histidine protein kinase; RBOH, NADPH oxidase.