Includes the study of how the environmental stimuli of light and gravity alter patterns of growth and development in plants. Molecular approaches are used to characterize proteins that are critically involved in mediating the coupling of light and gravity stimuli to morphogenic changes in plants. Studies of light-induced signal transduction leads to a focus on potential signaling proteins that function primarily or partially in the nucleus. Nuclear proteins recently characterized include an annexin, an apyrase (= NTPase), a CK II protein kinase, lamins, a nucleolin, protein phosphatases and Ran (a monomeric GTP-binding protein). For most of these proteins, their cDNAs have been characterized and the effects of light on the abundance of mRNAs that encode them have been documented. Several of them include the study of the phenotypes of transgenic Arabidopsis plants that ectopically express the sense or antisense versions of their genes. Antibodies to most of these proteins have been raised to help immunolocalize them and quantitate their expression. Most of the proteins carry out their nuclear functions in partnership with other proteins. To help define these binding partners the yeast two-hybrid system is being employed. Investigations of the molecular biology of these proteins should help to clarify how they function in plant photomorphogenesis.
Recently found is that the apyrase enzyme, which is primarily nuclear in etiolated plants, is localized primarily in the the plasma membrane in light-grown plants, with its active site facing out into the extracellular matrix. It thus qualifies as an ectoapyrase. Since ATP is the preferred substrate of this enzyme, its ECM localization raises the question of the function of extracellular ATP (xATP). It has been found that xATP occurs in soil environments and that the pea ectoapyrase, which is strongly expressed in roots, can not only hydrolyze phosphates from xATP, but also promote the uptake of the released phosphate. Surprisingly, it can also promote the uptake of inorganic phosphate and can complement a yeast mutant deficient in a high-affinity phosphate transporter. It has also been found that the Arabidopsis multi-drug resistance transporter, MDR1, can promote the transport of ATP out of yeast and plant cells, just as its homolog in vertebrates has been reported to do in animal cells. It has been found that the hydolysis of xATP by ectoapyrase and other ectophosphatases, which increases the steepness of the ATP gradient between the inside and outside of cells, increases the efficiency of toxin export across the MDR1 transporter both in transgenic yeast and in transgenic Arabidopsis plants.
For gravitational studies, a single-cell model system has been developed, germinating spores of Ceratopteris richardii, in which gravity orients the direction of nuclear migration and subsequent rhizoid development and growth. The utility of this system for defining the genes needed for gravity responsiveness is being investigated. A Shuttle experiment (STS-93, July 1999) has been completed which allows the identification of genes that are differentially expressed in microgravity and to examine the role of these genes in mediating the gravity response.
Affiliated Research Units
Now that you've used EUREKA to identify a faculty member whose research interests match your own, read about getting involved in research at The University of Texas at Austin.
The Office of Undergraduate Research recommends that you attend an info session before contacting faculty members about research opportunities. We'll cover the steps to getting involved, tips for contacting faculty, funding possibilities, and options for course credit.
If you aren't able to attend an info session, contact the Office of Undergraduate Research to schedule an appointment with an advisor.