On improving strigolactone mimics for induction of suicidal germination of the root parasitic plant Striga hermonthica

Abstract

Strigolactones (SLs) are plant hormones that regulate the branching of plants and seed germination stimulants of root parasitic plants. As root parasites are a great threat to agricultural production, the use of SL agonists could be anticipated to provide an efficient method for regulating root parasites as suicidal germination inducers. A series of phenoxyfuranone-type SL mimics, termed debranones, has been reported to show potent bioactivities, including reduction of the tiller number on rice, and stimulation of seed germination in the root parasite Striga hermonthica. To exert both activities, two substituents on the phenyl ring of the molecules were important but at least a substituent at the 2-position must be an electron-withdrawing group. However, little is known about the effect of the properties of the substituents at the 2-position on bioactivities. Here, we found that different substituents at the 2-position give different preferences for bioactivities. Halogenated debranones were more effective than the others and SL agonist GR24 for inhibiting rice tiller but far less effective in the induction of S. hermonthica germination. Meanwhile, nitrile and methyl derivatives clearly stimulated the germination of S. hermonthica seeds. Although their IC 50 values were 100 times higher than that of GR24 in the receptor competitive binding assay, their physiological activities were approximately 1/10 of GR24. These differences could be due to their uptake in plants and/or their physicochemical stability under our experimental conditions. These findings could support the design of more potent and selective SL agonists that could contribute to solving big agricultural issues.

Strigolactone mimic 2‐nitrodebranone is highly active in Arabidopsis growth and development

“…When compared with the optimized configurations, 2NOD displayed stronger selectivity against ShHTL7 when compared with GR24 (Figure S11b), which is in accordance with our experimental observations. Consistent with our results from the docking simulation analysis of 2NOD or GR24 with ShHTL7 (Figure S11), Takahashi et al reported that 2NOD was far less effective than GR24 in the induction of S. hermonthica germination (Takahashi et al, 2020). However, in contrast to the results in Arabidopsis, they showed that the activity of 2NOD is slightly weaker than GR24 in inhibiting rice tillering.…”

“…Consistent with our results from the docking simulation analysis of 2NOD or GR24 with ShHTL7 (Figure S11), Takahashi et al. reported that 2NOD was far less effective than GR24 in the induction of S. hermonthica germination (Takahashi et al ., 2020). However, in contrast to the results in Arabidopsis, they showed that the activity of 2NOD is slightly weaker than GR24 in inhibiting rice tillering.…”

Counteractive Effects of Sugar and Strigolactone on Leaf Senescence of Rice in Darkness

“…The germinated seeds were then transferred to a hydroponic culture medium [10] solidified with 0.6% (v/v) agar and grown under fluorescent white light (100 µmol m −2 s −1 ) with a 16 h light/8 h dark cycle at 25 • C for 10 days. Leaf segments, 2 cm long, were cut from the middle of the third leaf and the subsequent assay was performed as described previously [34].…”

Harmony but Not Uniformity: Role of Strigolactone in Plants

“…Originally, SLs were recognized as the stimulus for germination of parasitic plants [ 93 ]. For hyphal branching in AMF, SLs were also known as stimulants [ 9 , 10 , 93 ].…”

“…Originally, SLs were recognized as the stimulus for germination of parasitic plants [ 93 ]. For hyphal branching in AMF, SLs were also known as stimulants [ 9 , 10 , 93 ]. Furthermore, SLs were identified to have a positive influence on nodule formation in the interaction process of legume–rhizobium [ 39 ].…”