Methylation at the C-3′ in D-Ring of Strigolactone Analogs Reduces Biological Activity in Root Parasitic Plants and Rice

Muhammad Jamil,Boubacar A Kountche,Djibril Yonli,Faisal Aldossary,Imran Haider,Kun-Peng Jia,Stefan T Arold,Umar F Shahul Hameed,Tsuyoshi Ota,Ikuo Takahashi,Salim Al-Babili,Jian You Wang,Tadao Asami,Randa A Zarban

doi:10.3389/fpls.2019.00353

Abstract

Strigolactones (SLs) regulate plant development and induce seed germination in obligate root parasitic weeds, e.g. Striga spp. Because organic synthesis of natural SLs is laborious, there is a large need for easy-to-synthesize and efficient analogs. Here, we investigated the effect of a structural modification of the D-ring, a conserved structural element in SLs. We synthesized and investigated the activity of two analogs, MP13 and MP26, which differ from previously published AR8 and AR36 only in the absence of methylation at C-3′. The de-methylated MP13 and MP26 were much more efficient in regulating plant development and inducing Striga seed germination, compared with AR8. Hydrolysis assays performed with purified Striga SL receptor and docking of AR8 and MP13 to the corresponding active site confirmed and explained the higher activity. Field trials performed in a naturally Striga-infested African farmer’s field unraveled MP13 as a promising candidate for combating Striga by inducing germination in host’s absence. Our findings demonstrate that methylation of the C-3′ in D-ring in SL analogs has a negative impact on their activity and identify MP13 and, particularly, MP26 as potent SL analogs with simple structures, which can be employed to control Striga, a major threat to global food security.

Highlights

Strigolactones (SLs) are an intriguing class of plant hormones, which have attained immense importance during the past two decades because of their diverse biological roles in plant biology (Al-Babili and Bouwmeester, 2015; Waters et al, 2017)
We examined the potential of MP13 and MP26 in exerting SL growth-regulating activities
Application of GR24 and MP26 showed significant increase in plant height as compared to mock with dwarf rice plant while rice biomass remained unaffected by all SL analogs (Figure S1)

Summary

Introduction

Strigolactones (SLs) are an intriguing class of plant hormones, which have attained immense importance during the past two decades because of their diverse biological roles in plant biology (Al-Babili and Bouwmeester, 2015; Waters et al, 2017). Besides in-planta activities, SLs are released by plant roots into the rhizosphere as signaling molecules to establish beneficial symbiosis with arbuscular mycorrhizal (AM) fungi, by stimulating the branching of their hyphae (Akiyama et al, 2005; Akiyama and Hayashi, 2006; Besserer et al, 2006). This signal is perceived by seeds of root parasitic weeds of the Orobanchaceae family, which abuse SLs as germination signal, indicating the presence of a host that is needed for their survival as obligate parasites (Cook et al, 1966)

Methods

Results

Conclusion