Poster: Regulation of gene expression

Abs # 794: Transcriptional Regulation by the Auxin Response Factor MONOPTEROS

Presenter:	Krogan, Naden T, krogan@botany.utoronto.ca
Authors	Krogan, Naden T (A)   Ckurshumova, Wenzi  (A)   Berleth, Thomas  (A)
Affiliations:	(A): University of Toronto

The Arabidopsis MONOPTEROS (MP) gene plays a central role in embryo axis and vascular strand formation. MP encodes a transcription factor of the 'Auxin Response Factor' (ARF) family, whose members regulate the expression of auxin-induced genes by binding to conserved promoter 'Auxin Response Elements' (AuxREs). Several lines of evidence have implicated auxin in cell pattern formation. MP could therefore relay auxin signals in embryo axis patterning and vascular differentiation. Its target genes, however, are unknown. We have determined the expression profiles of numerous genes involved in vascular development and auxin signaling in backgrounds of varying MP activity. This has revealed many candidate MP transcriptional targets. To establish which of these MP-dependent genes are direct downstream targets, a mp mutant line has been generated containing a posttranslationally inducible MP transgene (employing the hormone binding domain of the glucocorticoid receptor). This MP:GR transgene successfully and reversibly rescues the mp mutant, providing a suitable tool for elucidating direct targets. A promising target revealed from this inducible system, the HD-ZIP III gene ATHB-8, has clear putative AuxREs in noncoding regulatory regions, further suggesting dependence on MP for its expression. This MP:GR line is currently being studied by microarray analysis to reveal potential downstream MP targets on a genome-wide scale.