Effects of triazole derivatives on strigolactone levels and growth retardation in rice

Abstract

We previously discovered a lead compound for strigolactone (SL) biosynthesis inhibitors, TIS13 (2,2-dimethyl-7-phenoxy-4-(1H-1,2,4-triazol-1-yl)heptan-3-ol). Here, we carried out a structure-activity relationship study of TIS13 to discover more potent and specific SL biosynthesis inhibitor because TIS13 has a severe side effect at high concentrations, including retardation of the growth of rice seedlings. TIS108, a new TIS13 derivative, was found to be a more specific SL biosynthesis inhibitor than TIS13. Treatment of rice seedlings with TIS108 reduced SL levels in both roots and root exudates in a concentration-dependent manner and did not reduce plant height. In addition, root exudates of TIS108-treated rice seedlings stimulated Striga germination less than those of control plants. These results suggest that TIS108 has a potential to be applied in the control of root parasitic weeds germination.

Figure 1. Syntheses of designed chemicals.

(A) Br₂, AlCl₃, ether; (B) 1,2,4-triazole, K₂CO₃, acetone; (C) R₂X, 60% NaH, DMF, reflux; (D) NaBH₄, MeOH.

Figure 2. Effect of chemicals on 2-week-old rice seedlings.

(A) epi-5DS levels in root exudates of 1 µM chemical-treated rice seedlings determined by LC-MS/MS. The data are means ± SD of three samples. (B) The length of 2nd leaf sheath in 10 µM chemical-treated rice. The data are means ± SD of six samples.

Figure 3. A comparison of the effects caused by TIS13 and TIS108 treatment.

(A) Chemical structures of strigolactone biosynthesis inhibitors. (B) epi-5DS levels in root exudates of chemical-treated rice seedlings determined by LC-MS/MS. The data are means ± SD of three samples. (C) The length of 2nd leaf sheath in 10 µM chemical-treated rice. The data are means ± SD of six samples.

Figure 4. Effects of TIS108 on 2-week-old rice seedlings.

(A) epi-5DS levels in roots and root exudates of TIS108-treated rice seedlings determined by LC-MS/MS. (B) Germination stimulant levels in culture media of 1 µM TIS108-treated rice seedlings using Striga seeds. DW, distilled water; GR24, 1 µM GR24; control, non-treated rice culture media; TIS108, culture media of 1 µM TIS108-treated rice; TIS108+GR24, culture media coincubated with 1 µM GR24 and 1 µM TIS108. The data are means ± SD of three samples.