2,3,5-Triiodo Benzoic Acid (TIBA)

Properties:

2,3,5-Triiodobenzoic acid (TIBA) is used to inhibit polar auxin transport. Stock solution 10 mM in dimethyl sulfoxide. Store at -20°C. Effective concentrations to inhibit are in the range of 20-40 µM

Molecular Target:

Acts through bundling of actin resulting in misplacement of auxin-efflux carriers. The bundling has been shown also for animal cells. Originally, TIBA was used in parallel with N-ethylmaleimide (NEM) as sulfhydryl blocker (Leopold 1962) and its inhibitory activity on auxin transport was found during studies on the influence of SH-rich proteins for auxin transport. NEM is a classical blocker of myosin function. Therefore, the actin bundling observed in response to TIBA might be caused by arrested myosin activity.

Specificity

Due to the mode of action (see above) it is expected that TIBA will also affect other SH-rich proteins, and thus is probably less specific than NPA.

Physiological Effects:

• Causes bundling of actin (Dhonukshe et al. 2008)
• Blocks root growth in a mode different from NPA (Rahman et al. 2007)

Further reading

Dhonukshe P, Grigoriev I, Fischer R, Tominaga M, Robinson DG, Hašek J, Paciorek T, Petrašek J, Seifertová D, Tejos R, Meisel LA, Zažímalová E, Gadella TWJ, Stierhof YD, Ueda T, Oiwa K, Akhmanova A, Brocke R, Spang A, Friml J (2008) Auxin transport inhibitors impair vesicle motility and actin cytoskeleton dynamics in diverse eukaryotes. Proc Natl Acad Sci USA 105: 4489-4494 This work shows that TIBA bundles actin in non-plant cells and suggests that this will impair the localization of efflux carriers