A Taylor-Made Design of Phenoxyfuranone-Type Strigolactone Mimic

Abstract

Strigolactones are a class of plant hormones that inhibit axillary bud outgrowth and are released from plant roots to act as a rhizosphere communication signal. The Orobanchaceae parasitic plant Striga hermonthica perceives strigolactone as its germination signal, indicating host presence. After germination, the Striga plant parasitises the host plant and suppresses host growth by draining photosynthetic products, water and other essential nutrients. Because of this way of life, this parasite threatens crop production in sub-Saharan Africa with infestation in crop fields and crop devastation. Crop protection in such areas is among the most concerning problems to be dealt with as immediately as possible. With respect to crop protection from Striga, many strigolactone agonists have been developed and used in research to reveal Striga biology, and have contributed to development of crop protection methods. However, an effective method has yet to be found. In a previous study, we reported debranones as a group of strigolactone mimics that inhibit axillary buds outgrowth with moderate stimulation activity for Striga germination. Debranones would be accessible because they are simply synthesized from commercially available phenols and bromo butenolide. Taking this advantage of debranones for Striga research, we tried to find the debranones stimulating Striga seed germination. To modulate functional selectivity and to enhance germination inducing activity of debranones, we studied structure–activity relationships. We investigated effects of substituent position and functional group on debranone activity and selectivity as a strigolactone mimic. As a result, we improved stimulation activity of debranones for Striga seed germination by chemical modification, and demonstrated the pharmacophore of debranones for selective modulation of distinct strigolactone responses.

Regulation of biosynthesis, perception, and functions of strigolactones for promoting arbuscular mycorrhizal symbiosis and managing root parasitic weeds

“…33,34 Introduction of two electron-withdrawing groups, Br and CN, on the benzene ring resulted in the enhancement of germination stimulation activity and reduction of tillering inhibitory activity. 35,36 This result suggests that further structural modification may afford more active germination stimulants which can be used as suicidal germination inducers. 37 In addition to debranone derivatives, among other SL agonists containing the D ring moiety, methyl phenolates (e.g.…”

“…) was developed as a SL agonist and is a potent inhibitor of tillering in rice, but a relatively weak germination stimulant for S. hermonthica seeds . Introduction of two electron‐withdrawing groups, Br and CN, on the benzene ring resulted in the enhancement of germination stimulation activity and reduction of tillering inhibitory activity . This result suggests that further structural modification may afford more active germination stimulants which can be used as suicidal germination inducers …”

Strigolactone: Pflanzenhormone mit vielversprechenden Eigenschaften

“…Die exakte Rolle und die Liganden der HTLs in nicht parasitären Pflanzen bleiben jedoch weiterhin unbekannt. [51] Genau wie füra ndere Pflanzenhormone kçnnen Affinitätsmessungen mit unterschiedlichen Te chniken durchgeführt werden, wie der isothermen Titrationskalorimetrie (ITC) [52] oder der Messung der thermischen Destabilisierung des Rezeptors nach Strigolacton-Zugabe. Dies wurde 2018 von Uraguchi et al demonstriert, die HTL der parasitären Pflanze Striga hermonthica nutzten, um nach synthetischen, keimungsstimulierenden Substanzen zu suchen.…”

“…Diese Te chnik wurde genutzt, um synthetische Debranon-Derivate zu entwickeln, die eine stark verbesserte keimungsfçrdernde Aktivitätf ür S.-hermonthica-Samen aufweisen. [51,[58][59][60] [53] Fluorogene Moleküle wie Yoshimulactone Green (YLG), [54] die nach ihrer Hydrolyse fluoreszieren, kçnnen Aufschluss über die chemische Struktur von synthetischen Molekülen geben, die um die Bindung konkurrieren, wie für S. hermonthica HTL7 beschrieben.…”

“…[57] Untersuchungen der Struktur-Aktivitäts-Beziehungen kçnnen auch in planta durchgeführt werden (indem Strigolacton-induzierte Phänotypen wie Blattseneszenz und Hemmung der Verzweigung verfolgt werden), um die Potenz von Strigolacton-Analoga zu analysieren (Abbildung 1). [51,[58][59][60]…”