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| role of auxin
in the growth, development and environmental
responses of plants |
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Mary
Helen M. Goldsmith, Ph.D.
Professor of Molecular,
Cellular & Developmental Biology
Professor in Forestry and Environmental
Studies (courtesy appointment)
Email: mary.goldsmith@yale.edu
Room: KBT 946A
Phone: (203) 432-3511/ (203) 432-3515
B.A. Cornell University
1955;
PhD. Harvard University, Radcliffe College
1959 |
The auxin indoleacetic acid is an important signal
for the growth and development of plants. Auxin
is produced in developing leaves. During its distribution
throughout the plant by a highly specific polar
transport, the hormone participates in regulating
cell division, elongation, and vascular differentiation
as well as mediating responses to environmental
signals such as light or gravity. Our interest
in polar auxin transport and auxin-induced growth
focuses on the role of H+- ATPases and ion channels
in cell elongation.
According to the acid growth hypothesis, auxin
stimulates the growth of plant cells by regulating
the activity of H+-ATPase in the plasma membrane.
Proton secretion by this transport enzyme acidifies
the cell walls increasing their extensibility.
The cells’ internal hydrostatic pressure then
extends the walls. Proton secretion also builds
up pH and electrical gradients that contribute
to the transport of ions and other solutes including
auxin. During the osmotic uptake of water accompanying
growth, plant cells maintain their internal solute
concentration through uptake of ions. Potassium
ions are essential for growth as well as opening
of stomata and flowers and rhythmic leaf movements.
If the concentration of K+ in the soil is above
0.2 mM, K+ enters the root passively through specific
voltage-sensitive channels in the cell membrane.
We discovered that one of the earliest responses
of cells stimulated to grow by auxin is a transient
depolarization of the cell membrane. This is followed
several minutes later by a hyperpolarization attributable
to stimulation of the proton pump. This drives
the potential of the plasma membrane sufficiently
negative for passive influx of K+ to occur. We
use patch clamping to investigate both the whole
cell and single channel currents underlying these
auxin-induced voltage changes. We are also examining
whether Ca++ modulates inward K+ channels in growing
cells during response to auxin.
Selected Publications
Senn, A., M.H.M. Goldsmith. (1988). Regulation
of electrogenic proton pumping by auxin and fusicoccin
as related to the growth of Avena coleoptiles.
Plant Physiol. 88:131-138
Kourie, J. & M.H.M. Goldsmith. 1992. K+ channels
are responsible for an inwardly-rectifying current
in the plasma membrane of mesophyll protoplasts
of Avena sativa. Plant Physiol. 98:1087-1097.
Spalding, E., C.L. Slayman, & M.H.M. Goldsmith,
A. Bertl. 1992. Ion channels in Arabidopsis plasma
membrane: Transport characteristics and involvement
in light-induced voltage changes. Plant Physiol.
99:96-102.
Spalding, E., M.H.M. Goldsmith (1993). Activation
of K+ channels in the plasma membrane of ATP produced
photosynthetically. Plant Cell 5:477-484.
Teaching
EVST 325b, MCDB 235b, F&ES 571b: Plants
and Agriculture in Temperate and Tropical Ecosystems.
MCDB 250 Biology of Plants.
Service
Advisory Committee, Program in Environmental
Studies.
Yale College Environmental Summer Internships,
chair since 1996.
Marsh Botanic Garden Steering Committee and former
director. Involved in the restoration of the garden
and development of its collections highlighting
plant communities, diversity, and environmental
change in New England.
Advisory Committee, YIBS Center for Field Ecology
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