Gibberellin (GA) regulates strigolactone (SL) biosynthesis S. Ito , M. Umehara, A. Hanada, S. Yoshida, J. Kyozuka, M. Ueguchi-Tanaka, M. Matsuoka, K. Shirasu, S. Yamaguchi, T. Asami Structure of SL (2’-epi -5-deoxystrigol: epi -5DS) Mock SL treatment Mock SL treatment Root parasitic weed germination Hyphal branching in arbuscular Cook et al., Science Wild-type SL deficient mycorrhizal fungi mutant Akiyama et al., Nature Shoot branching Umehara et al., Nature Many chemicals control SL biosynthesis Carotenoid Auxin Abscisic acid Ferguson et al., 2007 López-Ráez et al., 2010 Cytokinin PhosphateP Yoneyama et al., 2007 SLs One of the strigolactone biosynthesis inhibitors (TIS102) 0 µM 1 µM TIS102 concentration GA 3 reduces the epi -5DS level in rice root exudates N.D. GA 3 N.D. : Not detected ・ seed germination ・ stem elongation ・ flowering ・ fruit ripening ・ GA 3 branching GA 3 reduces the SL levels in rice Epi -5DS 2’-epi -orobanchol Roots control 0 0.1 1 10 100 5000 GA 3 concentration (nM) BL GR24 Root exudates GA 3 0 0.1 1 10 100 5000 GA 3 concentration (nM) BL GR24 Active GAs reduce the SL levels Roots GA 1 GA 8 GA 3 GA 1 GA 4 GA 8 Root exudate GA 3 GA 4 Structure of gibberellins GA 3 GA 1 GA 4 GA 8 GA 34 GA 3 also reduces the SL levels in GA biosynthesis mutant Roots osga3ox2 GA 3 concentration (nM) Root exudate WT GA defficient mutant WT osga3ox2 GA 3 doesn’t reduce the SL levels in GA signaling mutant Roots 5 cm WT gid2-2 GA 3 concentration (nM) Root exudate WT gid2-2 WT gid2-2 GA 3 concentration (nM) SL is not detceted in constitutive GA response mutant Root exudate 5 cm WT slr1 GA 3 concentration (nM) WT slr1 GA reduce the SL levels depending on GA signaling. GA 3 also reduces the SL levels in SL signaling mutant Roots Root exudate 0 0 50 WT WT d3 d3 mutant GA 3 concentration (nM) GA reduce the SL levels independent of SL signaling. GA reduces the transcript levels of SL biosynthesis genes carotenoid D17 (CCD7) D10 D17 (CCD8) D27 Strigolactones GA 3 concentration (nM) GA reduces the Striga germination stimulants in rice root exudates DW GR24 control GA 3 GA 3 +GR24 Root exudate GR24 1 µM, GA 3 10 nM GA-treated rice reduces the Striga infection ＊ ＊ ＊ ＊: P<0.05 Conclusion GA reduces the SL levels. the transcript levels of SL biosynthesis genes. the Striga infection. Controlling the GA biosynthesis or signaling pathway in plants might become one of the way to contol the root parasitic weed infection..