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Faculty
 Valerie M. Sponsel, Ph.D.
Associate Professor of Biology
Laboratory: BSE 3.208. Tel: (210) 458-5494
Office: BSE 1.642. Tel: (210) 458-5929
Fax: (210) 458-5658
Valerie.Sponsel@utsa.edu
Ph.D., University of Wales, U.K.
D.Sc., University of Bristol, U.K.
Research Interests
Plants, like animals, contain
hormones that can regulate growth and development. My research focuses on
the gibberellin group of plant hormones. Gibberellins are diterpenoids,
and more than 130 different gibberellins have been identified from plants,
and from some fungi including Gibberella fujikuroi, from which the
hormones derive their name. In plants, we know that one type of hormone
can control many different developmental processes. As an example,
gibberellins can regulate seed germination, stem growth, transition to
flowering, and fruit development. In many cases the regulation involves
interaction with other types of plant hormones too.
In my research lab we are looking at growth and development in the model
plant Arabidopsis thaliana, which is easy to grow, has a short life
cycle, has a small genome, and produces thousands of seeds per plant. By
making genetic mutants of Arabidopsis we are able to select for
mutant plants in which processes that are known to be controlled by
gibberellins are altered. For example, by screening for and selecting
plants that are extremely short or extremely tall we can investigate
whether these mutants are altered in their biosynthesis or response to
gibberellin. An investigation into which biochemical processes have been
altered or perturbed in a mutant can lead to a clearer understanding of
how those processes operate in wild-type individuals. In turn this
information may be use to determine how plant growth or development could
be manipulated in a specific manner to improve crop productivity and
yield.
Gibberellin/auxin interaction in Arabidopsis:
The tir3-1 mutant of Arabidopsis has altered transport of
the plant hormone, auxin, which is normally synthesized in shoot apices
and transported basipetally from the shoot apex to the root. The tir3-1
mutant has many phenotypic features consistent with altered auxin
transport such as reduced apical dominance and a reduction in the number
of lateral roots. Other phenotypic features can be reversed by treating
with bioactive gibberellins, suggesting that there is cross-talk between
auxins and gibberellins, either at the level of biosynthesis or signaling.
Our current research is investigating the effect of auxin on gibberellin
biosynthesis and signaling. The work involves determining hormone levels
by combined gas chromatography-mass spectrometry, measuring levels of
transcripts encoding genes for biosynthetic enzymes, and looking at
components in the gibberellin signal transduction pathway.
Opportunities exist in the lab for undergraduate and
graduate student research.
Recent Papers and Reviews
Desgagne-Penix I, Eakununkul S, Coles JP, Phillips
AL, Hedden P, Sponsel VM. The auxin transport inhibitor response 3
(tir3) allele of BIG and auxin transport inhibitors affect
the gibberellin status of Arabidopsis. Plant J. 41: 231-242 (2005).
Sponsel VM. Gibberellins. In: Encyclopedia of
Hormones and Related Cell Regulators (Henry, HL, Norman, AW eds. Elsevier,
San Diego, CA) vol.2 pp 29-40 (2003).
Sponsel VM, Hedden P. Gibberellin biosynthesis and
metabolism. In: Plant Hormones: Biosynthesis, Signal Transduction, Action!
(Davies, PJ ed. Kluwer, Dordrecht) pp 62-98. (2004).
Sponsel VM. Gibberellins. In: Plant Physiology. (Taiz,
L and Zeiger E., Sinauer, Sunderland MA) 4th edition. In press.
Publication date: April 2006.
Teaching Interests
Classes taught in the past five years:
Bio 1123 Introductory Biology 2 (Honors, team taught with David Senseman)
BIO 1143 Introductory Biology 3 (Honors and Regular sections)
HON 3253 Plants and Society
BIO 3343 Plant Science
BIO 4643 Medicinal Plants and BIO 6973 Special Topics in Medicinal Plants
BIO 4663 Plant Development and BIO 6973 Special Topics in Plant Development
BIO 6563 Food Science and Biotechnology
Graduate Advisor of Record for the Masters of Science in Biotechnology
Secretary and Treasurer of the International Plant Growth Substance Association (IPGSA) http://www.ipgsa.org/
Member American Society of Plant Biologists http://www.aspb.org/
Secretary Friends of Friedrich Wilderness Park http://www.fofriedrichpark.org/
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