Proteins anchor plant cells against water loss

Researchers led by Stanford University have identified two protein systems with opposing functions in the stability of plant cells under water deficit. The cellulose synthase complex, known as CSC, increases anchoring points between the cell wall and plasma membrane. Remorins, or REMs, limit this process. The study indicates a new cellular pathway associated with resilience to water loss stress.

The research analyzed structures described more than a century ago by the botanist Karl Hecht. Under conditions of water loss, the plasma membrane retracts relative to the cell wall. Part of it remains attached by filaments and attachment points, called Hechtian structures. The team showed that these anchorages keep the membrane connected to the wall during cell dehydration. Cells with more attachment points recovered better after water returned.

Experimental model

The work used roots of Arabidopsis thaliana as an experimental model. Researcher Yue Rui compared wild-type plants with genetically modified lines. The group applied live-cell imaging, protein mapping, genetics, confocal microscopy, and cryogenic electron tomography. The objective involved observing the interface between the cell wall and plasma membrane during hyperosmotic shock.

Scientists describe the cell's outer surface as the first line of perception and response to environmental stimuli. In plants, this interface includes the plasma membrane beneath the cell wall. The two structures remain associated by anchoring points. These points become evident during hyperosmotic shock, when severe water loss causes membrane retraction.

Cellulose complex

The cellulose synthase complex played a central role. According to the article, the density of CSCs in the plasma membrane correlated with resistance to hyperosmotic stress. Higher CSC density favored the maintenance of cell wall-membrane bonds. Cellulose deficiency produced the opposite effect, with greater plasmolysis and less recovery of root growth.

In assays with 0,28 molar sorbitol, wild-type roots showed a 52 to 57 percent reduction in growth. Cellulose-deficient mutants, such as cesa3je5, cesa6prc1-1, and cob-1, had a reduction equal to or greater than 75 percent. Expression of GFP-CELLULOSE SYNTHASE 3 in the cesa3je5 mutant restored root growth to wild-type levels.

Distinct effect

The results also pointed to a distinct effect of rhamnose, a component of the rhamnogalacturonan-I chain. rhm1-1, rhm1-2, and rhm1-3 mutants, deficient in rhamnose, experienced less growth reduction under hyperosmotic stress compared to the wild type. The researchers observed an increase in proteins associated with the CSC machinery in the rhm1-1 mutant. Among these were CESA1, CESA5, CESA6, CSI1, CSI3, PATROL1, and CMU1.

Remorins acted as negative regulators of anchorages. Under sorbitol treatment, REM1.2 formed nanodomains in about five minutes. These nanodomains appeared in the roots of five-day-old seedlings. Their density increased with the concentration of sorbitol. The study indicates that REMs restrict the abundance of CSCs, with the participation of SHOU4 and SHOU4L proteins.

Scientists propose a model in which CSCs function as stitching points between the membrane and the cell wall. By producing cellulose, the complex also attaches the membrane to the cell wall. REMs act as a brake on this system, limiting the amount of CSCs at the anchoring sites. When REMs are lacking, the number of CSCs increases in the membrane. The anchoring becomes firmer during stress.

The agronomic importance stems from the relationship between cellular water loss and common field stresses. The source cites drought, salinity, heat, and freezing as conditions associated with cellular water loss. Identifying these proteins opens possibilities for studying crop engineering to produce more stress-tolerant crops. The next step mentioned by Yue Rui involves observing the same mechanism in species with greater drought tolerance and verifying whether they exhibit more stable or denser anchoring points.

Further information at doi.org/10.1016/j.cell.2026.05.009