Regulation of Stem Gravitropic
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
a Masters student at Marshall, investigates the
interaction of auxin and ethylene in the
regulation of gravitropism.
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,
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.