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 procedures of the National Academy of Sciences (PNAS), plant genomic scientists at the Center for Genomics and Systems Biology at New York University discovered the missing piece in the molecular link between a plant’s perception of the dose of nitrogen in its environment and changes sensitive to dose in your biomass.
Taking a novel approach, the NYU researchers examined how increasing doses of nitrogen created changes in the expression of the entire plant genome 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 rate of reaction. Because transcription factors establish the rates at which gene transcription from DNA to RNA takes place, can directly compare with catalytic enzymes in the Michaelis-Menten model. This means that increasing the abundance of key transcription factors should be able to increase the rate of gene expression dependent on the dose of nitrogen and, consequently, the rate of plant growth, “said Gloria Coruzzi, Carroll & Milton Petrie Professor in the NYU Department of Biology and Center for Genomics and Systems Biology, and 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.
“By modeling the transcriptome kinetics underlying nitrogen dose detection using a classical principle of Michaelis-Menten kinetics, we discovered a regulatory gene whose increased expression can drive crop growth in low nitrogen soil,” he said. Coruzzi. “Because TGA1 is preserved in plants, including crops such as rice, tomato, and wheat, our findings have implications for improving the efficiency of nitrogen use in crops, which can benefit agriculture and sustainability ”
Biologists capture fleeting interactions between regulatory proteins and their genomic targets
Joseph Swift et al., “Dose-responsive transcriptome changes driven by Michaelis-Menten kinetics underlie plant growth rates.” PNAS (2020). www.pnas.org/cgi/doi/10.1073/pnas.1918619117
New york university
Boosting plant biomass: biologists discover molecular link between nutrient availability and growth (2020, May 11)
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