Agrobacterium T‐DNA gene 1 codes for tryptophan 2‐monooxygenase activity in tobacco crown gall cells

Abstract

Cloned tobacco crown gall tissue induced by the Agrobacterium tumefaciens C58 T‐DNA mutant pGV3132, defective for the T‐DNA‐encoded amihydrolase (iaaH), accumulates about 1000‐times more indole‐3‐acet‐amide (IAM) when compared to untransformed tobacco callus and crown gall tissue induced by a T‐DNA mutant defective for gene 1. In vitro experiments demonstrated that this IAM accumulation is correlated with the active conversion of Trp into IAM. The results presented in this report provide biochemical evidence that the T‐DNA gene 1 encodes a tryptophan 2‐monooxygenase (iaaM) activity in transformed plant cells. This gene cooperates with the gene 2‐encoded amidohydrolase (iaaH) in the T‐DNA‐controlled indole‐3‐acetic acid (IAA) biosynthesis pathway in crown gall cells.

Translation Start Sequences Affect the Efficiency of Silencing ofAgrobacterium tumefaciensT-DNA Oncogenes

“…These abnormally high phytohormone levels result from expression of three genes transferred stably into the plant genome from the A. tumefaciens tumor-inducing (Ti) plasmid: iaaM (Trp mono-oxygenase), iaaH (indole-3-acetamide hydrolase), and ipt (AMP isopentenyl transferase; Garfinkel et al, 1981;Ream et al, 1983). IaaM converts Trp into indole-3-acetamide, which IaaH converts into indole-3-acetic acid (auxin;Inzé et al, 1984;Schroeder et al, 1984;Thomashow et al, 1985Thomashow et al, , 1986Van Onckelen et al, 1986). Loss of either enzyme prevents auxin production.…”

Altered Growth and Wood Characteristics in Transgenic Hybrid Aspen Expressing Agrobacterium tumefaciens T-DNA Indoleacetic Acid-Biosynthetic Genes

“…The endogenous concentration of IAA can be altered by transforming plants with the Agrobacterium tumefaciens T-DNA IAA-biosynthetic genes iaaM and iaaH, encoding Trp-2-mono-oxygenase (Thomashow et al, 19 86;Van Onckelen et al, 1986) and indole-3-acetamide hydrolase (Schroder et al, 1984;Thomashow et al, 1984), respectively. These two enzymes catalyze a two-step biosynthesis of IAA from Trp via indole-3-acetamide.…”

Transgenic Tobacco Plants Coexpressing the Agrobacterium tumefaciens iaaM and iaaH Genes Display Altered Growth and Indoleacetic Acid Metabolism

“…The iaaM gene encodes an enzyme converting tryptophan to IAM2 (29,31), which is subsequently hydrolyzed to IAA by the action of the iaaH gene product (23,28). Plants expressing these IAA biosynthetic genes from promoters of different strength and tissue specificity could serve as a model system to manipulate endogenous IAA levels in vivo.…”