Flotillin proteins could help plant cells maintain their salt balance

A gene that could help plants cope with elevated salinity has been identified in the widely studied model plant species Arabidopsis thaliana¹. The finding, published in the Russian Journal of Plant Physiology, refines our picture of how proteins in plant membranes regulate the cellular ion balance.

The research focused on one of the genes that encode flotillin proteins—components of the cell membrane that are thought to be involved in a range of specialized cellular functions.

A research team from the Timiryazev Institute of Plant Physiology at the Russian Academy of Sciences, led by Yury Balnokin, used an Arabidopsis mutant with increased expression of the flotillin FLOT1 gene to investigate the gene’s potential role in salt tolerance.

“[We thought that] there could be a relationship between flotillin and salt tolerance via the functions of ion-transporting proteins localized to membrane nanodomains,” explains Balnokin.

Salinity is a major problem in many agricultural regions around the world, and can have a devastating impact on crop yields. It is caused by a range of factors including irrigation and drying climate, and while improved agricultural practices can help reduce salinity levels, increasing the salt-tolerance of the crops themselves is a highly active area of research.

The team observed that the FLOT1 mutation led to increased levels of FLOT1 expression in the roots. Mutants had lower concentrations of sodium ions (Na⁺) and elevated potassium ion (K⁺) levels than wild-type plants, along with larger plant organs. The mutant plants also formed a larger number of bubble-like vesicles in the cell’s gelatinous cytoplasm.

“The mutant had significant and quite pronounced phenotypic changes with only a relatively small increase in FLOT1 expression,” says Balnokin.

To test the effect of the mutation on salt tolerance, the researchers grew wild-type and mutant plants in a high-salinity medium for 20 days and then exposed them to salt for 8 hours. They found that the changes caused by the mutation were accentuated by saline conditions.

Growing plants in a saline medium led to increased expression of FLOT1 in both the mutant and wild type plants. The wild type specimens also underwent changes in cellular structure that made them more similar to the mutant, including a more vesicular cytoplasm and more fluid-filled microvacuoles.

While these findings do not directly show that FLOT1 increases salinity tolerance, they do point towards a role for FLOT1 in regulating the transport of Na⁺ and probably other ions.

The FLOT1 gene is activated under saline conditions, and many of the changes in response to salt – increased organ mass and changes in cellular structure – seem to be a consequence of increased FLOT1 expression. These findings, together with the presence of flotillin in nanodomains, suggest that flotillin influences ion homeostasis by affecting the distribution of transport proteins in membranes.