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•
Major
Research Goal
To elucidate the
regulation of ethylene biosynthesis in response to
environmental stress conditions and changes in
orientation to gravity.
•Ethylene Biosynthesis-Mediated
Regulation of Stem Gravitropic
Curvature
Plant gravitropism, the directional growth of a
plant or plant parts in response to the Earth's
gravitational field, is controlled by
growth-regulating substances and light. The
gaseous hormone ethylene plays a modulating role
in regulating the kinetics of the growth
asymmetries. Light also modulates gravitropic
curvature, an effect attributed to phytochrome
regulation, possibly through its interaction
with ethylene biosynthesis and response.
Previous research on dark-grown pea stems
demonstrated that ethylene production is
inhibited by a short-term red-light pulse, but
increased after horizontal placement. Reverse
transcriptase-polymerase chain reaction (RT-PCR)
analysis of the amount of mRNA produced by genes
that encode the ethylene biosynthetic enzymes
1-aminocyclopropane-1-carboxylic acid (ACC)
synthase (ACS) and ACC oxidase did not support
strong transcriptional regulation of these genes
by red light. Our current research project uses
the genetic model plant, mouse-ear cress (Arabidopsis
thaliana), to characterize the gravitropic
responses in reporter mutants which contain ACS
promoter:: reporter constructs, and mutants lacking specific forms of
the enzyme 1-aminocyclopropane-1-carboxylic
acid synthase (ACS), or of the red-light
photoreceptor, phytochrome.
Using MATLAB to
Process Images for the Analysis of Plant Organ
Growth and Curvature.
Image analyses of
plant growth phenomena can be achieved by a
number of commercially available software
programs. However, these programs require
considerable user manipulation when collecting
the measurements, making it time-consuming to
examine large sets of images. Additionally, the
software programs that process images do not
necessarily offer the ability to integrate
complex mathematical calculations within the
same program. Dr. Harrison in collaboration
with Dr. Sarra and Saveliev in the Department of
Mathematics, have developed MATLAB mathematical
software and its associated Image Processing
Toolbox to create a plant image analysis tool
for the collection and measurement of the growth
and curvature of plant stems and roots. Our
objectives were to create a tool that 1) uses a
single program to accomplish multiple steps in
image processing and analysis, 2) can be
modified for a variety of mathematical
measurements, and 3) has the potential to be
automated to process sets of images. The plant
image analysis tool first reduces the image of
the stem or root to an array of x- and
y-coordinates that define the center of the
organ. These coordinates are used for
measurements of overall growth, curvature,
angle, and point of maximum curvature (vertex).
Using this tool, we have been able to process
images collected from the hypocotyls of
horizontally-reoriented etiolated Arabidopsis
mutants associated with the 1-aminocyclopropane
carboxylic acid synthase (At-ACS) genes.
Current studies are using the plant image
analysis tool to evaluate gravitropic curvature
in pea stems and Arabidopsis roots and
inflorescence stalks, as well as for basic organ
growth studies.
A
photoacoustic spectroscopy (PAS)-laser system
has been constructed for the analysis of the
kinetics of ethylene, a plant hormone. The PAS
system is based on the generation of acoustic
waves caused as gas molecules absorb light and
then release the excess energy as heat. The
resulting thermal expansion of the sample leads
to the generation of acoustic waves that are
detected with a pressure-sensitive microphone.
The current research project uses the PAS
to evaluate the kinetics of ethylene production in
pea stems during gravitropism (the process of
orientation relative to the gravitational field).
 The
PAS project was supported by the National Research Initiative of the USDA Cooperative Research, Education and Extension Service,
2005-35304-16013.
 Mia Brown,
2005 NASA Scholarship awardee, investigated
whether ethylene biosynthetic genes are
expressed in larger amounts on the lower
compared to the upper side of
horizontally-placed stems. Specific ethylene
biosynthetic genes were evaluated in Arabidopsis seedlings carrying the gene’s
regulatory sequence joined to a reporter gene.
Her results suggest that At-ACS4 is
up-regulated during gravitropic curvature and At-ACS6 and
At-ACS8 may increase in
the area of curvature supporting a stimulatory
role for ethylene in upward curvature in Arabidopsis stems.
•
 Mia Brown and Mica Rivera, 2004
NASA Scholarship awardees, are investigated the
role of specific ACS forms in the regulation of
gravitropism in Arabidopsis seedling
stems. Their ongoing investigation measures the
kinetics of curvature in the wild type and in mutants
lacking specific ACS forms.
Jessica Casto,
a 2004 Summer Undergraduate Research Fellow,
analyzed the gravitropic curvature response in
Arabidopsis
seedling stems in wild type and phytochrome
mutants. Her research showed that mutants
lacking phytochrome A had greatly inhibited
curvature, while mutants lacking phytochromes B
(and related phytochrome forms D and E)
exhibited increased curvature. Jessica is a
current graduate student in the Dept. of
Biological Sciences at Marshall.
John Porter, a 2003 Summer
Undergraduate Research Fellow, found that
disruption of the Arabidopsis ACS4 gene
increases stem gravitropic curvature. Additionally,
preliminary RT-PCR analysis indicated that ACS4 is potentially regulated by red light
at the transcriptional level. John presented his
work at the annual meeting of the
American Society for Gravitational and Space
Biology in Huntsville, AL, and at the
14th International Conference on
Arabidopsis
Research in Madison, WI. John is
currently a graduate student in the Horticulture
Department at West Virginia University.
Previous Research Projects:
Ethylene Biosynthesis as an Indicator of
Stress in
Hydroponically-Grown Strawberries
Articles:
Harrison, M.A. 2006. Role of ethylene in the regulation of
stem gravitropic curvature. In: Ethylene Action in Plants,
Professor Dr. Nafees A. Khan (ed.), Springer-Verlag
GmbH Berlin Heidelberg,
pp 135-149.
Harrison, M.A. 2006. Plant hormones and signal transduction.
In: Plant Cell Biology, W.V. Dashek and M.H.
Harrison (eds), Science Publishers, Enfield, NH, pp 451-487.
Steed C.L., L.K. Taylor, and M.A. Harrison.
2004. Red-light regulation of ethylene biosynthesis and
gravitropism in etiolated pea stems. Plant Growth Regulation
43: 117-125.
Gonzales, D., J. Traylor, A. Hubbard,
B. Lowman, and M.A. Harrison. 1999. Growth and gravitropic
curvature in ethylene mutants of Arabidopsis thaliana. Proc.
WV Acad. Sci. 71: 33-42.
Presentations:
Harrison, M.A., P. Saveliev,
S. Sarra, and D. Silver.
2008. Using MATLAB to process images for the analysis of
plant organ growth and curvature. The 19th
International Conference on Arabidopsis Research,
Montreal, Canada.
Brown,
M.L. and M.A. Harrison. 2007. Ethylene regulation of
gravitropic curvature in Arabidopsis stems. Plant
Biology & Botany 2007: P32009. Joint Congress of the
American Society of Plant Biologists and the Botanical
Society of America, Chicago IL.
Brown,
M.L. and M.A. Harrison. 2007. Ethylene regulation of
gravitropic curvature in Arabidopsis stems. Proc.
WV Acad. Sci. 79: 24. Marshall University Sigma Xi
Research Day; the West Virginia Academy of Sciences,
Marshall University, WV.
Brown, M. and
M.A. Harrison. 2006. Ethylene regulation of the plant
response to gravity. Poster presented at the 2006 Sigma Xi
Research Day, Marshall University, Huntington, WV, and the
West Virginia Academy of Sciences, Shepherd, WV.
Porter, J.E., J.D. Hogan, and M.A. Harrison. 2004. The
interacting roles of light regulation and ethylene
biosynthesis in modulating hypocotyl gravitropism Poster
presented at the 15th International Conference on
Arabidopsis Research, Berlin, Germany.
Harrison, M.A. and J. E. Porter. 2003. Role of the
ethylene biosynthesis gene, 1-aminocyclopropane-1-carboxylic
acid synthase (ACS) in regulating stem gravitropism. Poster
presentation at meeting of
The American Society for Gravitational and Space Biology,
Huntsville, AL.
Porter, J. E. and M. A. Harrison 2003. Role of ethylene
biosynthesis in hypocotyl gravitropism. Poster presentation
at the
14th International Conference on Arabidopsis Research,
Madison, WI.
Harrison, M.A. 2002. Red-light regulation of ethylene
biosynthesis and gravitropism. Plant Biology
-PlantBiology2002:118. American Society for Plant
Physiologists, Denver, CO.
Harrison , M.A. and A.J. Porter. 2001. Evaluation of
red-light regulation of ethylene biosynthetic genes by
relative RT-PCR. The American Society for Gravitational
and Space Biology, Alexandria, VA.
Funded Projects:
NSF:
ADVANCE Institutional
Transformation Award: Advancing women in science,
math and engineering at Marshall. (2006-2009) $1,200,000
(PI: M. Harrison; Co-PIs: B. Delidow, E. Murray, J. Silver,
K. Miezio).
WV
EPSCoR Seed Grant: Cross-Disciplinary Research Initiative in
Biological Mathematics. (2006) $5,000 (PI: S. Collier,
co-PI’s M. Harrison, P. Saveliev, S. Sarra)
MUF: College of Science
Multidisciplinary Research Initiative: A College-Wide
Faculty Development Proposal to Foster Collaboration,
$50,000 (primary author: M. Harrison)
WV EPSCoR Seed Grant: Light regulation of
ethylene biosynthesis in Arabidopsis: Promoter analysis of
1-aminocyclopropane-1-carboxylic acid synthase genes.
(2003) $20,000 (PI: M. Harrison).
American Society for Gravitational and
Space Biology: Light regulation of ethylene biosynthesis
during gravitropic curvature in Arabidopsis.
(2002) $10,000 (PI: M. Harrison).
WV EPSCoR: Research Proposal
Preparation Mini-Grant: Evaluation of red-light regulation
of ethylene biosynthetic genes.
(2002) $5,000 (PI: Marcia A. Harrison).
USDA: CREES: NRI-Equipment Grant:
Gradient thermal cycler acquisition to enhance plant gene
expression research.
(2001) $10537 (PI: M. Harrison).
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