Pandya-Kumar, N., Institute of Plant Sciences, Agricultural Research Organization (ARO), Volcani Center, Bet Dagan, 50250, Israel
Shema, R., Institute of Plant Sciences, Agricultural Research Organization (ARO), Volcani Center, Bet Dagan, 50250, Israel, Robert H. Smith Faculty of Agriculture Food and Environment, Hebrew University of Jerusalem, Rehovot, 76100, Israel
Kumar, M., Institute of Plant Sciences, Agricultural Research Organization (ARO), Volcani Center, Bet Dagan, 50250, Israel
Mayzlish-Gati, E., Institute of Plant Sciences, Agricultural Research Organization (ARO), Volcani Center, Bet Dagan, 50250, Israel
Levy, D., Institute of Plant Sciences, Agricultural Research Organization (ARO), Volcani Center, Bet Dagan, 50250, Israel
Zemach, H., Institute of Plant Sciences, Agricultural Research Organization (ARO), Volcani Center, Bet Dagan, 50250, Israel
Belausov, E., Institute of Plant Sciences, Agricultural Research Organization (ARO), Volcani Center, Bet Dagan, 50250, Israel
Wininger, S., Institute of Plant Sciences, Agricultural Research Organization (ARO), Volcani Center, Bet Dagan, 50250, Israel
Abu-Abied, M., Institute of Plant Sciences, Agricultural Research Organization (ARO), Volcani Center, Bet Dagan, 50250, Israel
Kapulnik, Y., Institute of Plant Sciences, Agricultural Research Organization (ARO), Volcani Center, Bet Dagan, 50250, Israel
Koltai, H., Institute of Plant Sciences, Agricultural Research Organization (ARO), Volcani Center, Bet Dagan, 50250, Israel

Strigolactones (SLs) are plant hormones that regulate shoot and root development in a MAX2-dependent manner. The mechanism underlying SLs' effects on roots is unclear. We used root hair elongation to measure root response to SLs. We examined the effects of GR24 (a synthetic, biologically active SL analog) on localization of the auxin efflux transporter PIN2, endosomal trafficking, and F-actin architecture and dynamics in the plasma membrane (PM) of epidermal cells of the primary root elongation zone in wildtype (WT) Arabidopsis and the SL-insensitive mutant max2. We also recorded the response to GR24 of trafficking (tir3), actin (der1) and PIN2 (eir1) mutants. GR24 increased polar localization of PIN2 in the PM of epidermal cells and accumulation of PIN2-containing brefeldin A (BFA) bodies, increased ARA7-labeled endosomal trafficking, reduced F-actin bundling and enhanced actin dynamics, all in a MAX2-dependent manner. Most of the der1 and tir3 mutant lines also displayed reduced sensitivity to GR24 with respect to root hair elongation. We suggest that SLs increase PIN2 polar localization, PIN2 endocytosis, endosomal trafficking, actin debundling and actin dynamics in a MAX2-dependent fashion. This enhancement might underlie the WT root's response to SLs, and suggests noncell autonomous activity of SLs in roots. © 2014 New Phytologist Trust.