Quantitative evaluation of the biological activity of various brassinosteroids using spiral root induction in rice seeds

Bunta Nishikawa; Kotaro Mori; Seisuke Takimoto; Bunta Watanabe; Midori Matsuo; Takeshi Nakano; Yoshiaki Nakagawa; Hisashi Miyagawa

doi:10.1584/jpestics.D23-044

Quantitative evaluation of the biological activity of various brassinosteroids using spiral root induction in rice seeds

J Pestic Sci. 2023 Nov 20;48(4):218-224. doi: 10.1584/jpestics.D23-044.

Authors

Bunta Nishikawa¹, Kotaro Mori¹, Seisuke Takimoto^{1

2}, Bunta Watanabe³, Midori Matsuo¹, Takeshi Nakano⁴, Yoshiaki Nakagawa¹, Hisashi Miyagawa¹

Affiliations

¹ Graduate School of Agriculture, Kyoto University.
² Central Pharmaceutical Research Institute, Japan Tobacco Inc.
³ Chemistry Laboratory, The Jikei University School of Medicine.
⁴ Graduate School of Biostudies, Kyoto University.

Abstract

Spiral roots are induced in germinated rice seeds through treatment with nanomolar brassinosteroids (BRs) but not with other plant hormones. Here, we determined the minimum effective concentration (MEC) of various BRs to induce spiral roots in germinated rice seeds. The reciprocal logarithm of MEC, pMEC, was used as the BL-like activity index, which was linearly correlated with the reciprocal logarithm of a 50% effective dose (pED₅₀) as evaluated in the rice lamina inclination assay. Furthermore, a ligand-receptor docking simulation was performed against the BL receptor complex, Arabidopsis thaliana BRI1/SERK1, and the binding free energy (ΔG_bind) was calculated for the tested BRs. The ΔG_bind calculation was performed using the molecular mechanics/generalized Born surface area method on an ensemble of uncorrelated snapshots collected via molecular dynamics to predict biological activity.

Keywords: MM/GBSA; MM/PBSA; brassinosteroids; docking simulation; spiral root induction.