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Robert Schmidt
Robert Schmidt
Division of Biological Sciences
University of California, San Diego

Research Interests

Our research interests are directed towards understanding the regulation of gene expression in plants and its impact on plant development. We have focused on two areas of study using maize as our experimental system; the mechanisms controlling maize flower development and the regulation of zein seed storage protein gene expression within developing seeds.

We are using a combination of genetics, transposon mutagenesis, heterologous hybridizations and reverse genetics to identify and clone genes controlling floral morphogenesis in maize. Since the maize flower (a grass flower) represents a dramatic departure from the standard dicot flower, we are interested to see what parallels exists between patterns of regulatory gene expression in maize and Arabidopsis, a model dicot plant on which much of current understanding of flower development is based. To this end we have identified orthologs in maize of important floral homeotic genes from Arabidopsis. How these genes control aspects of maize flower development are being explored through a combination of classical and reverse genetic approaches that allow us to identify mutant alleles containing transposon insertions, in situ hybridization analyses, and studies of ectopic gene expression in transgenic plants.

In addition to this line of investigation we have targeted a number of genetically defined loci affecting aspects of maize inflorescence development for transposon mutagenesis. The cloning and characterization of these genes is in progress. As evident from the above description, research in our lab involves a combination of field, greenhouse and bench work. Our studies are facilitated by our having greenhouses and several acres of field space available on campus as well as fruitful collaborations with some of the nation's largest hybrid seed companies. These studies are contributing to our understanding of the mechanisms controlling flower development among one of the most agriculturally important groups of angiosperms, the cereals. This research is also of potential value to systematist and evolutionists addressing questions regarding evolutionary relatedness among the organs of distantly related angiosperms, like maize and Arabidopsis.

In addition to the above mentioned studies we are exploring the role of several different DNA binding proteins in regulating expression of the zein multi-gene family during maize endosperm development. These include the bZIP proteins Opaque-2 and OHP1, and the DOF protein PBF. A variety of techniques, including in vitro mutagenesis, transgenic expression in heterologous systems, transient assays in suspension cell cultures, and analyses of DNA-protein interactions are being used to evaluate the role of these proteins in zein gene expression. Using both classical and reverse genetic approaches we are analyzing the effects that mutations in these regulatory genes have on endosperm development and seed protein gene expression. Determining the individual role each plays in promoting proper developmental expression of zein genes, and elucidating what interactions may exist between the products of these regulatory loci are long-term goals. These efforts are important to furthering our understanding of plant gene regulation and may prove useful for future efforts aimed at exploiting seeds as tools for the production of selected protein products.