A waxy layer for salt tolerance
Most plants don’t like to much salt. They get pretty stressed out about it, lose their appetite, or to be more accurate their chloroplasts, and die slowly. Still, there are plants that flourish under salty conditions. Not surprisingly researchers are curious how plants adapted that don’t stress out over an extra pinch of salt.
Chinese researchers show in a new study “BOUNDARY OF ROP DOMAIN3 Modulates Salt Tolerance by Mediating Cuticle Wax Synthesis” that one of these adaptations is the doubling of the wax layer that covers the leaves.
The researchers were curious to the adaptions of plants to prevent respiration during salt stress. To find those the researchers searched for a tale cress plant that did not show signs of salt stress when growing in salty soil. This plant, that they gave the nickname tos1, turned out to have extra shiny and waxy leaves.
Negative influence
The first thing the researchers did was determine the responsible gene. This turned out to be DBR3. The researchers also observed that the protein encoded by DBR3 was located in the mitochondria. This was a surprise as fatty molecules for the wax layer are synthesised in the endoplasmic reticulum.
In tos1 there is less DBR3 present. Therefore, to find out how DBR3 is influencing salt tolerance, the researchers created a plant with more DBR3. This plant was extra sensitive to salt. Which indicates that DBR3 is negatively influencing salt tolerance.
Extra thick wax layer
Subsequently the researchers analysed the wax layer of tos1 plant, which was twice as thick. Especially the amount of fatty acids, alkanes and ketones where increased. With as effect that tos1 plants were sweating less, losing less water.
To find out how BDR3 manages this, the researchers studied how the gene expression changed during salt stress in tos1 plants. They noticed that genes needed for the wax production showed increased activity in tos1. They also noticed that genes involved in the production of glycerolipid were less active.
This information about how the gene expression changes in tos1 plant compared to plants with a working DBR3 gene explains why tos1 plants have a thicker wax layer. What is still unclear is how DBR3 managed this, as it is not directly involved by the regulation of gene expression or the production of the lipids of the wax layer. The next step is then, as the researchers say, to characterise the DBR3 protein.
Literature
Miao, R., Q. Yang, W. Xiang, et al. 2025. “BOUNDARY OF ROP DOMAIN3 Modulates Salt Tolerance by Mediating Cuticle Wax Synthesis.” Plant, Cell & Environment 0: 1–17. https://doi.org/10.1111/pce.70300.
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