Plant & zo
The science of plants and more
Salty soil and salty water are fatal to plants. It pushes them out of balance. To avoid this damage, plants have a salt-action plan. They turn on genes that help dealing with too much salt in a plant. They adjust their growth, avoiding the salty ground. But plants need salt as well, in small doses. They can’t completely shut it out. So how do they recognise when there is too much salt?
To find out Dutch researchers turned to the cell wall. Asking the question: does it change when there is too much salt? The cell wall consists of long chains of cellulose hold together by pectin. Together they make a strong but flexible cell wall. Analysing this, the researchers noticed that when roots are in salty water, the structure of pectin changes.
This discovery appears to be at the start of the uncovering of an elegant system
Pectin methyl esterase is the enzyme responsible for the structure change of pectin. It removes a methyl group. When there is lots of salt this enzyme works harder. It removes more methyl groups. Calcium in contrast is slowing this enzyme down. If there is enough calcium, it can cancel the promoting effect of salt. The interesting part is, the researchers not only observed this for the enzyme speed, but also for some other salt responses. Such as the turning on of salt-action genes. These are only turned on in response to salt, but only when there is not enough calcium present.
How the cell exactly notices the changes in the cell wall is not clear yet. A group of cell wall sensors are the most likely candidates. Plants in which these cell wall sensors don’t work are more sensitive to salt. Suggesting that these cell wall sensors prevent a reaction to salt, unless they notice a change in the cell wall that indicates that there is too much salt is present.
This discovery appears to be at the start of the uncovering of an elegant system. With it, the plant can react on cell as well as organ level when there is too much salt. It can make sure the plant stays in balance.
Nora Gigli-Bisceglia, Eva van Zelm, Wenying Huo, Jasper Lamers, Christa Testerink; Arabidopsis root responses to salinity depend on pectin modification and cell wall sensing. Development 15 June 2022; 149 (12): dev200363. doi: https://doi.org/10.1242/dev.200363