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Research reveals nitrogen’s role in Circadian cycle
A group of researchers, which includes faculty from Dartmouth, has
determined that organic nitrogen controls a genetic network in plants that
regulates both the plant’s nitrogen metabolism and its circadian clock.
C. Robertson McClung (Photo by Joseph Mehling ´69)
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The study was conducted by researchers at Dartmouth, New York University’s
Center for Genomics and Systems Biology, Chile’s Papal Catholic University, and
Cold Spring Harbor Laboratory. The study, titled, “Systems approach identifies
an organic nitrogen-responsive gene network that is regulated by the master
clock control gene CCA1,” was published in the March 25 issue of the
Proceedings of the National Academies of Science.
The circadian clock controls the plant’s response to the time of day,
available sunlight, and seasons. Understanding the clock’s underlying genetic
mechanisms contributes to efforts to help improve plant productivity and can
possibly lead to growing crops that are more resistant to stressful soil or
climate conditions.
“Nitrogen is a key component of proteins and other cellular matter, and
insufficient nitrogen frequently limits plant growth,” says C. Robertson
McClung, professor of biological
sciences and an author on the paper. “Our study provides evidence that a
plant’s nitrogen nutrition, in other words how much nitrogen is in the plant,
and circadian clock function are intimately linked and mutually regulate each
other.”
Plants get their nitrogen from the soil, where it is usually found in
inorganic form as nitrate. As plants take up the nitrate, it is combined with
the products of photosynthesis to make amino acids such as glutamate and
glutamine that, in turn, are primary indicators of the abundance of
nitrogen in the plant.
The circadian clock controls a plant's response to the time of day, sunlight,
and seasons. (Photo: iStockphoto.com)
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The research team studied the effects of glutamate and glutamine on the
master clock control gene called CCA1. This study indicates that, in plants,
anticipating daytime and photosynthesis, which enables the assimilation of
inorganic nitrogen into amino acids, may represent one of the important
functions of the clock.
“To our knowledge, this is the first manuscript that uses a systems approach
to identify organic nitrogen-responsive gene networks in plants,” says lead
author Rodrigo Gutiérrez, a faculty member both at New York University and at
Papal Catholic University. “The systems biology approach provides an emerging
view of the circadian clock as an integrator of metabolism, physiology, and
gene function over time.”
In addition to Gutiérrez and McClung, Xiaodong Xu, a postdoctoral fellow at
Dartmouth, was also an author on the paper. Other authors include: Gloria
Coruzzi (the senior author on the study), Trevor Stokes, Karen Thum, Mariana
Obertello, Manpreet Katari, Alexis Dean, and Damion Nero with New York
University; and Milo Tanurdzic with Cold Spring Harbor Lab in New York.
This work was funded by grants to Coruzzi from the National Institutes of
Health, the Department of Energy, and the National Science Foundation, and a
grant from the National Science Foundation to
McClung.
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