Poster: Regulation of gene expression

Abs # 793: Regulation of thiamin biosynthetic genes by cellular demand for thiamin pyrophosphate

Presenter:	Tunc, Meral , tuncmeral@yahoo.com
Authors	Shintani, David Ken (A)   Tunc, Meral  (A)
Affiliations:	(A): University Of Nevada, Department of Biochemistry

Thiamin pyrophosphate (TPP) is an essential enzyme cofactor required for the viability of all organisms. While TPP can be synthesized by plants and microbes, humans and animals must obtain TPP as free thiamin from dietary sources. Although plants are an important dietary source of thiamin, little is known about how its synthesis is regulated in plants. Analyses of the Arabidopsis genome have identified plant orthologs of known microbial thiamin biosynthetic genes, including the E. coli ThiE, ThiC, and ThiM genes and the yeast Thi4 and Thi80 genes. Currently, very little is known about how plant thiamin biosynthetic genes are regulated. Previous studies in bacteria and fungi have shown that the expression of a number of thiamin biosynthetic genes is tightly regulated by cellular demands for TPP. Although much less is known in plants, it has been reported that the expression of the plant ThiE and Thi4 genes is repressed in the presence of exogenous thiamin. These observations suggest that like in microbial systems, thiamin biosynthesis in plants is tightly regulated at the level of gene expression. In order to determine whether this regulation extends to all plant thiamin biosynthetic genes, we are conducting transcriptional profiling studies on the effect of cellular demands for TPP on the plant ThiE, ThiC, ThiM, Thi4 and Thi80 genes. Quantitative RT-PCR analyses will be performed on thiamin auxotrophic Arabidopsis mutants and wild type Arabidopsis plants grown in the presence and absence of exogenous thiamin. These results will contribute greatly to our understanding of how thiamin biosynthesis is regulated in plants.