Overcoming salt stress with a one-two punch
Plants don’t like too much salt, still there are plants that thrive in a salty environment. Now Japanese researchers show that Vigna marina thanks its extreme salt tolerance due to a two-pronged approach.
Vigna marina is a plant that lives on tropical beaches. As a result, this plant is salt tolerant. But surprisingly, Vigna marina is more salt tolerant than its close relatives which also live on the beach. It is also closely related to a salt sensitive crop species. The researchers asked themselves therefore: how does Vigna marina manage this?
To investigate this the researchers studied first where in Vigna marina the salt accumulates. But the researchers noticed that in Vigna marina there was hardly any salt accumulated, when it grew in a salty environment. Vigna marina did not in as much keep salt outside, but it was actively showing it the door.
The researchers discovered that the pumping out of salt out of the plant was keeping a diurnal rhythm. Whereby, during the day, when the plant takes up more water — and thus more salt — the plant pumps out more salt than during the night. The responsible pump turned out to be SOS2. The gene encoding this protein is active during the day, but rests at night.
The SOS1 gene in Vigna marinaI is extra attractive to gene activators
Subsequently the researchers compared this pattern of SOS2 activity in Vigna marina with its nearest relatives. In each of the salt tolerant relatives SOS2 showed the same diurnal activity pattern. But not in the salt sensitive related crop species.
Still the researchers where not completely satisfied. Diving deeper into the salt tolerance of Vigna marina the researchers focused their attention to another salt pump, SOS1. This gene appeared to be constantly active in Vigna marina, it even did a bit extra during salt stress. In contrast, in Vigna marina nearest relatives, SOS1 was only active during salt stress. And in the salt sensitive crop relative, SOS1 wasn’t turned on at all. The reason why SOS1 is constantly on in Vigna marina, the researchers suspect, is that this gene is extra attractive to gene activators.
Because of this tow-pronged approach Vigna marina manages to survive in salty environments. First of all, through actively pumping out salt all the time, salt does not get a chance to accumulate in the plant. But even in the case salt does manages to find its way deeper into the plant, then the second salt pump is there to pump it out. This approach might turn out to be interesting for breeders of salt tolerant crops.
Literature
Noda, Y., Wang, F., Chankaew, S., Ariga, H., Muto, C., Iki, Y., Ohashi, H., Takahashi, Y., Sakai, H., Iseki, K., Ogiso-Tanaka, E., Suzui, N., Yin, Y.-G., Miyoshi, Y., Enomoto, K., Kawachi, N., Somta, P., Furukawa, J., Tomooka, N. and Naito, K. (2025), Diurnal Regulation of SOS Pathway and Sodium Excretion Underlying Salinity Tolerance of Vigna marina. Plant, Cell & Environment. https://doi.org/10.1111/pce.15402
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