The T‐region of Ti plasmids codes for an enzyme synthesizing indole‐3‐acetic acid

Abstract

Gene 2 from the T region of Ti plasmids appears to be expressed both in eucaryotic and in procaryotic systems. In transformed plant cells it participates in auxin‐controlled growth and differentiation, and in bacteria it is expressed into a defined protein of M_r 49000. We investigated the possibility that it codes for an enzyme involved in auxin biosynthesis. Only extracts from Escherichia coli cells expressing gene 2 hydrolyzed indole‐3‐acetamide into a substance which was unambiguously identified as indole‐3‐acetic acid. The same reaction was found in Agrobacteria containing gene 2, but not in strains lacking the gene. Extracts from tobacco crown gall cells, but not from non‐transformed cells, showed the same enzyme activity, and the reaction product was also identified as indole‐3‐acetic acid. The results indicate that gene 2 of the T region, which participates in tumorous growth of plant cells, codes both in bacteria and in plants for an amidohydrolase involved in the biosynthesis of the plant hormone indole‐3‐acetic acid.