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Full Stream Name: Epidermal Cell Fates and Pathways

Research Educator: Tony Gonzalez

Principal Investigator: Alan Lloyd

Credit Options: Spring & Fall

How is a cell’s fate determined?

This stream uses a comprehensive genetics approach to investigate mechanisms that lead to developmental cell fate decision events giving rise to terminally differentiated organs. In addition the stream studies pigment biosynthetic pathways that occur in those cells and are part of the differentiation process. Students will design and pursue experiments using a broad range of genetic strategies such as classical, molecular, forward and reverse genetics. In the process students will learn how to clone genes, engineer DNA, generate mutant and transgenic organisms, document and analyze data, and more. While this lab focuses on plants as experimental organisms, all the technologies learned in this stream are common to research in all modern molecular/genetic model organisms.

Over the years, many mutants and genes involved in the trichome (hair), testa (seed coat) and anthocyanin (red pigments common to flowering plants) pathways have been isolated. Much of this work has centered on identifying and characterizing the genes and proteins from Arabidopsis that physically interact in a single combinatorial transcription factor complex that regulates all of these pathways. We know a great deal about where and how these genes are expressed, how the proteins interact, and where they are located at the subcellular level.

Recently, a focus on identification of downstream transcriptional targets of this complex has lead to the identification of two key targets, both of which turn out to be transcription factors themselves. These both pleiotropically control several of the above-mentioned epidermal cell fate pathways.

In one aspect of this stream, students will perform a broad and rigorous molecular/genetic analysis of these two key regulatory loci, the Transparent Testa Glabra2 (TTG2) locus and the Glabra2 (GL2) locus. Students will learn and think about plant developmental processes at both the organismic-systems level and the extreme reductionist levels.

In another aspect, some students will be exploring the regulation of a novel plant pigment pathway, the red betalains. Betalains are interesting because they completely replace the biological role of anthocyanin pigments in a narrowly restricted group of plants, the Caryophyllales, which includes beets, spinach, and cactus. As mentioned above, anthocyanins are regulated by the combinatorial transcription factor complex that also regulates epidermal developmental events. One of the important questions we want to address, is how the betalain pathway is regulated. Is it regulated by the same complex that regulates anthocyanins? Is it co-regulated with other epidermal cell fate pathways? Presently there is virtually no information about betalain pathway regulation at the molecular level.

The course will emphasize hypothesis testing, experimental design, and the use of a wide range of technologies commonly used with modern model molecular/genetic organisms such as: mutagenesis and enhancer/suppressor mutant screens; map-based gene cloning; gene expression studies from single-gene RT-PCR or hybridization to whole genome DNA array-based analysis; transgenic organism production such as gene overexpression or suppression, protein epitope tagging, promoter-reporter construction, leading to confocal or other microscopic analysis technologies; protein-protein studies utilizing yeast 2-hybrid or in vitro analysis and more. The experiments performed by this stream will most likely lead to one or more publications with stream members as authors. These publications should be definitive publications characterizing the biology of two key regulators of plant epidermal cell fate and the regulation of the betalain pathway.

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