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| Alan Lloyd | |
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Associate Professor Ph.D. Stanford University, 1993 Office MBB 1.448
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| Epidermal
cell fate determination—trichome differentiation. In plants, the control of cell fate is a central issue during plant development. One main focus of my lab is to use trichome (plant hair) initiation as a simple and amenable model system to study the control of plant cell fate determination. Arabidopsis trichomes are single epidermal hair cells that originate from a field of undifferentiated epidermal cells and are distributed regularly on the leaf surface. They typically have three branches, and are highly polyploid. Trichomes can protect against heat and water loss and herbivore attack. Over the years, many trichome initiation mutants have been identified. For example, mutations in Transparent testa glabra1 (TTG1) are pleiotropic, affecting trichome initiation, anthocyanin synthesis, seed coat mucilage production, and root hair placement; mutations in Glabra1 (GL1) lead only to a loss of trichome initiation; Glabra3 (GL3) mutants have fewer and less branched trichomes. TTG1 encodes a WD40 protein, GL1 encodes a Myb protein, and we have recently shown that GL3 encodes a bHLH protein. Using a combination of genetics, molecular biology, and biochemistry, we are defining the specific regions of these and other cell-fate regulatory proteins that interact, characterizing the very early stages of the trichome cell fate decision, and studying how the wild-type leaf is able to create a very regular pattern of trichomes on the mature leaf surface. Seed coat (testa) differentiation Because mutations in TTG1 also lead to a loss of seed coat mucilage, we have become interested in the differentiation of the Arabidopsis seed coat. This is a relatively simple organ consisting of 5 cell layers surrounding the embryo. We have characterized the stages in its late differentiation in wild type plants and we are now studying the affect that various mutations have on this process. These include both extant and new mutations isolated in our lab. Recombinant Inbred Line construction The goal of this project is to contribute to the development of resources for both our lab and the plant science community that allow for the expanded use of natural genetic variation in reaching the goal of assigning a function to each Arabidopsis gene. We are developing several new sets of mapped Recombinant Inbred Lines (RILs). Simple Sequence Length Polymorphisms (SSLPs) are being used to define the genetic distance between all pairs of about 100 wild collected lines. Preliminary data indicate that these lines are highly polymorphic for this type of marker and this type of analysis is very amenable to robotic automation. We intend to generate maps with a density of approximately 6 centiMorgans. All lines will be made publicly available through the established stock centers and the data will be available to freely download through the Internet. Conventional mutational genetics and other methodologies used exclusively in a limited number of well-characterized laboratory strains of Arabidopsis, will not be able to reach the goal of a complete functional genomic analysis. We are hoping to contribute to a well-recognized need to include the large amount of available natural variation in the large-scale analysis of gene function in this species. The role of Apyrase and P-glycoprotein in toxin resistance. My lab collaborates with the lab of Dr. Stan Roux on the characterization of the role of extracellular phosphatases, particularly apyrase, in cellular toxin resistance and efflux mechanisms. We have found that these extracellular ectophosphatases play a fundamental role in the well known Multi Drug Resistance phenomenon. We have discovered a set of chemical inhibitors to ectophosphatases using an automated robotic screen for enzymatic inhibition. We have gone on to show that these inhibitors have profound biological activity in reversing multi drug resistance in bacteria and cancer cells and that these inhibitors may allow for a dramatic reduction in the amount of herbicides and other pesticides that are applied to the environment. These findings have broad implications in both agriculture and clinical pharmacology and we are pursuing the development of several practical applications of this technology. |
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