Regulation of IAA—Amino Acid Conjugate Formation in Carrot Tissues11Agrobacterium tumefaciens

Abstract

Regulation of IAA-amino acid conjugate formation was examined in cultured carrot tissues transformed with Agrobacterium tumefaciens harbouring aux− Ti plasmids. IAA-conjugate formation in carrot tissues transformed with aux− Ti plasmids was induced by exogenously-applied IAA. When these tissues were treated with an inhibitor of protein synthesis (cycloheximide) before IAA treatment, the induction of IAA-conjugate formation was completely inhibited. By contrast, pre-treatment with an inhibitor of RNA synthesis (actinomycin D) before IAA treatment reduced induction of IAA-conjugate formation. These results suggest that IAA-inducible IAA-conjugate is catabolized by enzyme(s) and the formation of conjugated IAA is regulated at the transcriptional level in carrot. Presumably, in carrot tissues transformed with wild-type or cyt− Ti plasmids, the same mechanism(s) exists and the free IAA content in the carrot tissues is maintained at a low level.