Inactivation of auxin in tobacco transformed with the indoleacetic acid-lysine synthetase gene of Pseudomonas savastanoi.

The iaaL gene of Pseudomonas syringae, subspecies savastanoi, encodes an indoleacetic acid (IAA)-lysine synthetase. To determine the effects of converting IAA to IAA-lysine in whole plants, the iaaL gene was fused to a constitutive plant promoter and introduced into tobacco plants. Biochemical analyses show that endogenous IAA is reduced by up to 19-fold in iaaL plants. Tobacco plants expressing the iaaL gene display reduced apical dominance, reduced rooting, and inhibition of vascular differentiation. The phenotypic effects of iaaL gene expression are reverted by crossing iaaL plants with plants that overproduce IAA. These data indicate that iaaL can act as an anti-auxin gene in vivo and confirm the role of auxin in the control of apical dominance, root growth, and vascular differentiation in whole plants.