Identification of Auxin Response Factor-Encoding Genes Expressed in Distinct Phases of Leaf Vein Development and with Overlapping Functions in Leaf Formation.

Based on mutant phenotypes the gene acts in several developmental processes including leaf vein development. Since overlapping functions among genes are common, we assessed the related and genes for potential overlap in expression during vein development using in-situ hybridization. Like was expressed in preprocambial and procambial cells. was also expressed in procambial cells, close to and during vein differentiation. was expressed in differentiating vessel elements. To assess if genes with vein expression have overlapping functions, double mutants were generated. While and mutants formed leaves normally, double mutant combinations of with or resulted in a breakdown of leaf formation. Instead, novel structures not present in any of the single mutants formed. The results implicate and in rosette leaf formation and suggest that their functions overlap and act in parallel with in this process. The observed vascular expression patterns suggest unique functions ( and ) and potentially overlapping functions ( and ) in vein development. Since double mutants do not form leaves, assessment of their potential combined action in vein development will require the use of conditional mutants.