A Ph.D. Thesis Proposal

PROJECT SUMMARY
The broad aim of this project is to develop a set of molecular tools, namely promoters that drive transcription to the root, for use in studying root biology. These promoters will then be used to study the function of ATP citrate lyase (ACL), a cytosolic enzyme whose immediate product is acetyl-CoA. The acetyl-CoA produced by ACL is used in formation of secondary metabolites including suberin, and flavonoids and isoflavonoids used in plant protection or signaling. ACL mRNA is present to high levels in root tips and vasculature; its function there is unknown.

The first step in this project is to identify a promoter that can be used to direct expression of transgenes to soybean or Arabidopsis root. A root-preferential promoter would allow directed study of genes of interest, and could also be used for agronomic purposes. Three promoters I am targeting for further study are the promoter of the soybean gmrp2 gene, the promoter of the maize zrp2 gene, and the sterol-inducible GVG promoter system (Aoyama and Chua, 1997). Northern blots have confirmed the pattern of root-preferential mRNA accumulation of the soybean GMRP2. Phage that may contain the gmrp2 promoter have been isolated from a genomic library, and are being sequenced to identify the promoter region. ZRP2 mRNA accumulates in the root cortex in maize. This pattern holds true for the transgenic zrp2-uidA maize. However, the zrp2 promoter acts in a specific, but not root-preferential, manner in soybean and Arabidopsis. Soybean and Arabidopsis plants have been produced which are designed to overexpress the Arabidopsis ACL-B protein under the control of the zrp2 promoter. These show no apparent phenotypic difference from wild-type plants. Some of the soybeans (in the T2 generation) may have elevated ACL-B protein levels in the leaves as detected by Western blot analysis. The GVG promoter system will be tested in soybean and Arabidopsis using the GUS reporter gene before it is used to direct expression of other transgenes.

It is possible that at some point in the future I will be able to post copies of my posters here. Whenever I get some papers published I will add links to those. Otherwise, if you are interested in what I do, please ask! I'll be happy to talk about ATP citrate lyase and soybean roots for hours on end (and even give the story of how my project has changed over the past 4+ years).

10/30/01