Abstract
The plant hormone, auxin, regulates various aspects of plant growth and development. However, the molecular mechanism of auxin action is still unclear. Therefore, bio-probes that modulate auxin action are useful tools for study on auxin signaling. In the screening program to search for auxin signaling inhibitors by mean of transgenic Arabidopsis plant harboring early auxin-responsive promoter and reporter gene, GUS (β-glucuronidase), we found terfestatin A (trfA) as a specific inhibitor of auxin signaling from culture bloth of Streptomyces sp. F-40. TrfA competitively inhibited the expression of early auxin-responsive Aux/IAA genes and also displayed competitive effects on auxin-induced cell division and elongation in Arabidopsis. In contrast to auxin action, trfA showed no effects on the gene expression induced by other plant hormone. From these results, trfA would be specific antagonist on auxin action that lead to early auxin-responsive gene expression, suggesting trfA might bind unknown auxin receptor in competitive manner.
