UTSA Biology 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.