Plants can adjust their shape, size and number of organs, grow according to gravity and light, and regenerate damaged tissues, through the action of the plant hormone auxin. Another versatile signal comes from Ca2+, which is a crucial second messenger for many cellular processes during responses to a wide range of endogenous and environmental signals. Auxin is a good candidate for one of the Ca2+-activating pathways but little is known about its role. De Vriese et al. screened a biologically annotated chemical library for inhibitors of an auxin (2,4-D)-induced Ca2+ response in order to better understand the molecular mechanism of auxin-induced Ca2+ signaling and to explore the role of Ca2+ in cellular auxin responses. They defined 67 confirmed inhibitors:
- Four are related fenamate-type chemicals (FFA, NFA, TFA and flunixin meglumine);
- Thirteen have reported protonophore activities;
- Bepridil, a known calcium-channel blocker that alters vacuolar morphology.
Further exploration of these inhibitors will lead to a better understanding of auxin-induced Ca2+ entry and its relevance for auxin responses. (Summary by Francesca Resentini) Plant Physiol. 10.1104/pp.18.01393