A new lead chemical for strigolactone biosynthesis inhibitors

Abstract

Several triazole-containing chemicals have previously been shown to act as efficient inhibitors of cytochrome P450 monooxygenases. To discover a strigolactone biosynthesis inhibitor, we screened a chemical library of triazole derivatives to find chemicals that induce tiller bud outgrowth of rice seedlings. We discovered a triazole-type chemical, TIS13 [2,2-dimethyl-7-phenoxy-4-(1H-1,2,4-triazol-1-yl)heptan-3-ol], which induced outgrowth of second tiller buds of wild-type seedlings, as observed for non-treated strigolactone-deficient d10 mutant seedlings. TIS13 treatment reduced strigolactone levels in both roots and root exudates in a concentration-dependent manner. Co-application of GR24, a synthetic strigolactone, with TIS13 canceled the TIS13-induced tiller bud outgrowth. Taken together, these results indicate that TIS13 inhibits strigolactone biosynthesis in rice seedlings. We propose that TIS13 is a new lead compound for the development of specific strigolactone biosynthesis inhibitors.

Fig. 1

Screening of the chemicals that induce outgrowth of second tiller bud in 2-week-old rice seedlings. (A and B) Length of the second tiller in seedlings treated with 10 μM of the chemicals. (C and D) Plant height of seedlings treated with 10 μM of the chemicals. The data are means ± SD of three samples. (E) Structures of chemicals that induced tiller bud outgrowth in A and B. (F and G) Two-week-old rice seedling treated with or without chemicals (TIS13 or TIS29). Scale bars in F and G indicate 5 and 1 cm, respectively. White arrowheads indicate second tillers.

Fig. 2

epi-5DS levels in roots and root exudates of chemical-treated rice seedlings determined by LC-MS/MS. (A) Effect of 10 μM TIS13 and TIS29. (B) Effect of varying concentrations of TIS13. (C) Effect of 10 μM uniconazole and paclobutrazol. The data are means ± SD of three samples.

Fig. 3

Effect of GR24 on tillering of 2-week-old rice seedlings treated with TIS13. (A) The lengths of second tillers in 3 μM TIS13-treated rice with or without 1 μM GR24. (B) Plant height in 3 μM TIS13-treated rice with or without 1 μM GR24. The data presented are means ± SD of six samples. (C and D) Two-week-old rice seedlings. Scale bars in C and D indicate 5 and 1 cm, respectively. The white arrowhead in D indicates a second tiller.

Fig. 4

Estimation of germination stimulant levels in culture media of 2-week-old seedlings using Striga seeds. DW, distilled water; GR24, 1 μM GR24; control, non-treated rice culture media; TIS13, culture media of TIS13-treated plants; TIS13 + GR24, culture media co-incubated with 1 μM GR24 and TIS13. The data are means ± SD of three samples.