A new regulatory element enables bacterial uptake by plant cells
Nitrogen is essential for growth and development of plants. Although, it is widely available, this is often not in a form that is easily taken up by plants. One group of plants did find a way around this and symbiose with nitrogen fixing bacteria. For this the plants take up these nitrogen fixing bacteria, and house them in specific organs, nodules.
But which trait is enabling this is not completely clear. Known is that this trait most likely is acquired once by the las common ancestor.
First researchers thought that this trait must be a gen. But studying the genomes of plants that do and don’t symbiose with nitrogen fixing bacteria did not result in any candidates.
Regulatory element
That made a group of German, France and Japanese researchers look to regulator elements in the promotor of an essential gen, NIN, that is needed for the uptake and housing of nitrogen fixing bacteria. The promoter of a gene is located in front of the protein coding part of a gene and contains instructions in the form of regulatory elements for gen regulators.
The NIN gene occurs in both plants that do and don’t symbiose with nitrogen fixing bacteria. By comparing the NIN promoter of 37 plants the researchers discovered that only NIN promoters of plants that do symbiose with nitrogen fixing bacteria contain a regulatory element that the researchers called PACE.
Bacterial up take
Subsequently the researchers showed that genes with a PACE regulatory element in their promoter are active in the cells where nitrogen fixing bacteria enter the plant. The researchers also showed that in absence of a PACE regulatory element the NIN-gene is not active in the presence of nitrogen fixing bacteria, and that the plant is not taking these up.
In addition, the researchers placed the PACE regulatory element in front of the tomato NIN-gene. Tomato normally does not symbiose with nitrogen fixing bacteria. But when there was a PACE regulatory element in front of the tomato NIN-gene, then that gene was just as active as a NIN-gene from plants that do symbiose with nitrogen fixing bacteria. It is, therefore, the PACE regulatory element and not the NIN-gene, that gives plants the trait to take up nitrogen fixing bacteria.
Literature
Cathebras, C., Gong, X., Andrade, R.E. et al. A novel cis-element enabled bacterial uptake by plant cells. Nat. Plants (2026). https://doi.org/10.1038/s41477-025-02161-z
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