Dr. Heike Winter
News Services, 919/515-3470
Plants Respond Quickly to Changes in Gravity, Environment
sample microarray. Lighter colored genes
are being expressed and darker colored genes
are not being expressed in this snapshot
When a plant is blown by the wind, flipped over, or
has its roots disturbed by an animal or a rock, specific
genes responsible for keeping the plant stable and
its roots and shoots growing respond very quickly,
many within one minute of the stimulus.
the findings of a research team from North Carolina
State University studying the effects of both
mechanical stimulation – forces like wind, temperature,
and water – and gravitational stimulation to
the root tips of the plant model Arabidopsis, or mustard
The team – consisting of botany graduate student
Jeffery M. Kimbrough; Dr. Heike Winter Sederoff, research
assistant professor of botany; Dr. Christopher Brown,
director of the North Carolina Space Initiative; Dr.
Wendy Boss, professor of botany; and post-doctoral
researcher Dr. Raul Salinas-Mondragon – also
discovered the specific genes that responded to the
different types of stimulation.
The research, which was funded by NASA, was published
in the September issue of Plant Physiology.
team used a technique called whole-genome microarray
analysis to take multiple snapshots of all
the plant’s genes during different time points – 2
minutes, 5 minutes, 15 minutes, 30 minutes and 60 minutes – after
both gravitational and mechanical stimulation.
Gravitational stimulation was applied by rotating
Arabidopsis seedlings 135 degrees from a vertical orientation,
or essentially flipping the seedling over so the shoot
would face down toward the ground on an angle and the
root would face up to the sky on an angle.
showed that 65 of the plant’s
roughly 24,000 genes responded specifically to gravitational
Arabidopsis seedlings like this one are used to study the
effects of mechanical and gravitational stimulation
To reproduce mechanical stimulation, the researchers moved the Arabidopsis seedlings in a back and forth motion for five seconds, similar to what a strong
gust of wind might do.
The results showed that 26 genes responded specifically
to mechanical stimulation.
also discovered that about 7 percent of the plant’s
genes responded to both mechanical and gravitational
stimulation. Sederoff says these
were mostly general plant growth genes that respond
to many different stimuli.
“The rapidity of the response of some of the
plant genes was a surprise to us,” Sederoff says. “This
research shows plants can quickly distinguish between
mechanical and gravitational stimulation.”
That’s important, she says, because it could
lead to more clues about how crops survive in different
climates on Earth. Also, agencies like NASA want to
learn more about how plants would grow on planets with
different gravitational forces than Earth’s.
The researchers plan to continue their work in this
area, examining the effects of other types of stimulation
and different varieties of plants.
- kulikowski -
to editors: An abstract of the paper follows.
Fast and Transient Transcriptional Network of Gravity
and Mechanical Stimulation in the Arabidopsis Root
Authors: Jeffery M. Kimbrough, Raul Salinas-Mondragon,
Wendy F. Boss, Christopher S. Brown and Heike Winter
Sederoff, North Carolina State University
Published: September 2004 in Plant Physiology
Abstract: Plant root growth is affected by both gravity and
mechanical stimulation (Massa GD, Gilroy S 
Plant J 33: 435–445). A coordinated response
to both stimuli requires specific and common elements.
To delineate the transcriptional response mechanisms,
we carried out whole-genome microarray analysis of
Arabidopsis root apices after gravity stimulation (reorientation)
and mechanical stimulation and monitored transcript
levels of 22,744 genes in a time course during the
first hour after either stimulus. Rapid, transient
changes in the relative abundance of specific transcripts
occurred in response to gravity or mechanical stimulation,
and these transcript level changes reveal clusters
of coordinated events. Transcriptional regulation occurs
in the root apices within less than 2 minutes after
either stimulus. We identified genes responding specifically
to each stimulus as well as transcripts regulated in
both signal transduction pathways. Several unknown
genes were specifically induced only during gravitropic
stimulation (gravity induced genes). We also analyzed
the network of transcriptional regulation during the
early stages of gravitropism and mechanical stimulation.