Nitrate Controls Gene Expression in Legumes

Legumes form nodules on their roots to take up nitrogen. They will stop the nodule production when nitrogen is plentiful, but precisely how nitrate presence controls nodule formation in these plants has been a mystery. The researchers from Japan have found that interactions between proteins and nitrate can induce and repress genes, controlling nodulation with potential applications in sustainable agriculture. The study was published in The plant cell.

The research team from the University of Tsukuba has shown that the different DNA-binding properties between proteins that establish nodule development determine if genes involved in a symbiosis that govern nodulation turn on or off and that this gene expression is nitrate-induced.There was no clear understanding of the molecular activity determining how legumes stop nodulation in the presence of excess nitrate. The research identified transcription factors in legumes that involved nodule formation, but that’s just part of the story. To examine these molecular interactions, the researchers analyzed RNA molecules and plant traits using proteins from Lotus japonicus

Researchers found some proteins have dual functions. They act as master regulators for nitrate-dependent gene expression. The new protein was also found in the binding sites and compared they were to previously known ones. Their findings reveal basic principles relating to NLP-regulated transcription of symbiotic genes inhibiting nitrate nodulation.

Some NLPs are found in cell nuclei in response to nitrate and stop nodule production, while others constantly aggregate in nuclei irrespective of nitrate levels. The location of the NLPs in the cell matters because translation happens in the cell’s cytoplasm. If changes to proteins occur after the genetic code has been read, it could explain how these NLPs access protein-protein interactions and regulate genes.