RAPID COMMUNICATION Strigolactones affect lateral root formation and root-hair elongation in Arabidopsis Yoram Kapulnik • Pierre-Marc Delaux • Natalie Resnick • Einav Mayzlish-Gati • Smadar Wininger • Chaitali Bhattacharya • Nathalie Se ´jalon-Delmas • Jean-Philippe Combier • Guillaume Be ´card • Eduard Belausov • Tom Beeckman • Evgenia Dor • Joseph Hershenhorn • Hinanit Koltai Received: 11 August 2010 / Accepted: 25 October 2010 Ó Springer-Verlag 2010 Abstract Strigolactones (SLs) have been proposed as a new group of plant hormones, inhibiting shoot branching, and as signaling molecules for plant interactions. Here, we present evidence for effects of SLs on root development. The analysis of mutants flawed in SLs synthesis or signaling suggested that the absence of SLs enhances lateral root formation. In accordance, roots grown in the presence of GR24, a synthetic bioactive SL, showed reduced number of lateral roots in WT and in max3-11 and max4-1 mutants, deficient in SL synthesis. The GR24-induced reduction in lateral roots was not apparent in the SL signaling mutant max2-1. Moreover, GR24 led to increased root-hair length in WT and in max3-11 and max4-1 mutants, but not in max2-1. SLs effect on lateral root formation and root-hair elongation may suggest a role for SLs in the regulation of root devel- opment; perhaps, as a response to growth conditions. Keywords GR24 Á Lateral root Á Root development Á Root hair Á Strigolactone Abbreviations CCD7 Carotenoid cleavage dioxygenase 7 CCD8 Carotenoid cleavage dioxygenase 8 SL Strigolactone WT Wild type Introduction Strigolactones (SLs) or closely related metabolites have recently been found to be a new group of plant hormones. Studies of Arabidopsis, pea and rice mutants flawed in SL production or signaling (e.g., Gomez-Roldan et al. 2008; Umehara et al. 2008; Vogel et al. 2009) have revealed SLs roles in plant biology: they are suggested to play a pivotal role in the regulation of aboveground plant architecture (e.g., Gomez-Roldan et al. 2008; Umehara et al. 2008; Vogel et al. 2009). Among the several mutants that were identified in Arabidopsis as involved in the SLs pathway are max2 plants, which are mutated in an F-box protein which is suggested to be involved in SL signaling (Bennett Y. Kapulnik and P.-M. Delaux have equal contribution. Electronic supplementary material The online version of this article (doi:10.1007/s00425-010-1310-y) contains supplementary material, which is available to authorized users. Y. Kapulnik Á N. Resnick Á E. Mayzlish-Gati Á S. Wininger Á C. Bhattacharya Á E. Belausov Á H. Koltai (&) Institute of Plant Sciences, Agricultural Research Organization (ARO), The Volcani Center, PO Box 6, Bet Dagan 50250, Israel e-mail: hkoltai@volcani.agri.gov.il P.-M. Delaux Á N. Se ´jalon-Delmas Á J.-P. Combier Á G. Be ´card Surfaces Cellulaires et Signalisation chez les Ve ´ge ´taux, Universite ´ de Toulouse, UPS, UMR 5546, BP 42617, 31326 Castanet-Tolosan, France P.-M. Delaux Á N. Se ´jalon-Delmas Á J.-P. Combier Á G. Be ´card UMR 5546, BP 42617, 31326 Castanet-Tolosan, France T. Beeckman Department of Plant Systems Biology, VIB, Technologiepark 927, 9052 Ghent, Belgium T. Beeckman Department of Plant Biotechnology and Genetics, Ghent University, Technologiepark 927, 9052 Ghent, Belgium E. Dor Á J. Hershenhorn Department of Phytopathology and Weed Research, Newe-Ya’ar Research Center, PO Box 1021, Ramat-Yishay, Israel 123 Planta DOI 10.1007/s00425-010-1310-y