Poster: Transcription Regulation

Abs # 1058: Iron Uptake in Arabidopsis

Presenter:	Colangelo, Elizabeth P, colangelo@dartmouth.edu
Authors	Colangelo, Elizabeth P (A)   Guerinot, Mary Lou  (A)
Affiliations:	(A): Dartmouth College, Department of Biological Sciences

Iron deficiency is the most prevalent human nutritional disorder. In addition, plant growth is often limited by iron availability. Since most people obtain their dietary iron from plants, understanding how plants acquire iron may lead to improvements in human nutrition as well as improvements in crop yields. Our lab is identifying components involved in iron uptake to better understand this process in Arabidopsis. In response to iron deprivation, Arabidopsis induce both ferric-chelate reductase activity and ferrous iron transport activity. We have now identified genes that encode the ferric-chelate reductase ( FRO2 ) and the main ferrous iron transporter ( IRT1 ) in Arabidopsis. By microarray analysis, we have identified several iron-regulated transcription factors and have begun to analyze their contribution to regulation of the iron deficiency response. One of these, FIT1 (Ferrous-deficiency Induced Transcription Factor 1), belongs to a group of bHLH transcription factors that recognizes the E-box consensus sequence 5’-CANNTG-3’. Putative E-box sequences are located in the promoters of IRT1 and FRO2 indicating that FIT1 may directly induce transcription of these iron uptake genes. FIT1 shows induced expression in iron deficient roots, specifically in the epidermis, coincident with the pattern seen for FRO2 and IRT1 . fit1 knockout plants are chlorotic and eventually die if not watered with a commercial iron source, which is similar to the phenotype of irt1 knockout plants. Expression of both IRT1 and FRO2 is altered in fit1 knockout plants relative to wild type plants but is unchanged in plants overexpressing FIT1 mRNA from the 35S promoter. Microarray analysis of the fit1 mutant is currently in progress in order to identity other potential FIT1 target genes.