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Plant scientists have long known that crop yields are proportional to the dose of nitrogen fertilizer, but increased use of fertilizers is costly and environmentally damaging. Until now, the underlying mechanisms by which plants adjust their growth according to nitrogen dose were unknown, a key finding that could help improve plant growth and limit the use of fertilizers.
In a new study published in the Proceedings of the National Academy of Sciences (PNAS), plant genomics scientists at the Center for Genomics and Biology Systems at New York University discovered the missing piece of the molecular link between a plant’s perception of the nitrogen dose in its environment and dose-sensitive changes in its biomass.
Using a novel approach, NYU researchers examined how increasing doses of nitrogen created changes in plant genome expression as a function of time. They then used mathematical models to investigate the rate of change of messenger RNA (mRNA) for thousands of genes within the genome to this experimental setup.
The researchers discovered that the dynamics of mRNA responses to nitrogen dose were governed by simple principles of enzyme kinetics (rates of enzyme-catalyzed reactions) first described by Michaelis-Menten in 1913. In fact, the authors discovered that the Michaelis-Menten kinetics could model the rate of change in gene expression in 30 percent of the nitrogen-sensitive genes.
“According to the classic Michaelis-Menten kinetic model, changing the abundance of enzymes will affect the maximum possible reaction rate. Because transcription factors establish the rates at which gene transcription from DNA to RNA takes place, they can be directly compared to catalytic enzymes in the Michaelis-Menten model. This means that increasing the abundance of key transcription factors should be able to increase the nitrogen dose-dependent gene expression rate and, consequently, the growth rate of plants, “said Gloria Coruzzi, professor at Carroll & Milton Petrie at the Department of Biology and Center for Genomics & Systems Biology, and the lead author of the article.
The research team found that increasing the level of transcription factor TGA1 accelerated the rates of gene expression sensitive to nitrogen dose and the growth rate of plants. Plants that overexpressed TGA1 had increased growth rates in response to nitrogen, reaching three times more plant biomass than wild-type plants.
