Evidence for species-dependent biosynthetic pathways for converting carlactone to strigolactones in plants.

Moe Iseki,Kasumi Shida,Masaharu Mizutani,Takatoshi Wakabayashi,Hirosato Takikawa,Yukihiro Sugimoto,Kazuma Kuwabara

doi:10.1093/jxb/erx428

Abstract

Strigolactones (SLs), comprising compounds with diverse but related chemical structures, are determinant signals in elicitation of germination in root parasitic Orobanchaceae and in mycorrhization in plants. Further, SLs are a novel class of plant hormones that regulate root and shoot architecture. Dissecting common and divergent biosynthetic pathways of SLs may provide avenues for modulating their production in planta. Biosynthesis of SLs in various SL-producing plant species was inhibited by fluridone, a phytoene desaturase inhibitor. The plausible biosynthetic precursors of SLs were exogenously applied to plants, and their conversion to canonical and non-canonical SLs was analysed using liquid chromatography-tandem mass spectrometry. The conversion of carlactone (CL) to carlactonoic acid (CLA) was a common reaction in all investigated plants. Sorghum converted CLA to 5-deoxystrigol (5-DS) and sorgomol, and 5-DS to sorgomol. One sorgomol-producing cotton cultivar had the same SL profile as sorghum in the feeding experiments. Another cotton cultivar converted CLA to 5-DS, strigol, and strigyl acetate. Further, 5-DS was converted to strigol and strigyl acetate. Moonseed converted CLA to strigol, but not to 5-DS. The plant did not convert 5-DS to strigol, suggesting that 5-DS is not a precursor of strigol in moonseed. Similarly, 4-deoxyorobanchol was not a precursor of orobanchol in cowpea. Further, sunflower converted CLA to methyl carlactonoate and heliolactone. These results indicated that the biosynthetic pathways of hydroxy SLs do not necessarily involve their respective deoxy SL precursors.

Highlights

Strigolactones (SLs) were first isolated from cotton root exudates and identified as germination stimulants of witchweed seeds (Cook et al, 1966)
These results indicated that the biosynthetic pathways of hydroxy SLs do not necessarily involve their respective deoxy SL precursors
Since the beginning of this century, significant physiological functions of SLs have been revealed, including the induction of the symbiotic association between plant roots and mycorrhizal fungi (Akiyama et al, 2005), inhibition of bud outgrowth to decrease shoot branching (Gomez-Roldan et al, 2008; Umehara et al, 2008), and regulation of root architecture (Brewer et al, 2013). These findings provided a rational explanation for the long unresolved question of why host plants produce and secrete SLs that trigger the germination of root parasitic weeds in their rhizosphere

Summary

Introduction

Strigolactones (SLs) were first isolated from cotton root exudates and identified as germination stimulants of witchweed seeds (Cook et al, 1966). Since the beginning of this century, significant physiological functions of SLs have been revealed, including the induction of the symbiotic association between plant roots and mycorrhizal fungi (Akiyama et al, 2005), inhibition of bud outgrowth to decrease shoot branching (Gomez-Roldan et al, 2008; Umehara et al, 2008), and regulation of root architecture (Brewer et al, 2013). These findings provided a rational explanation for the long unresolved question of why host plants produce and secrete SLs that trigger the germination of root parasitic weeds in their rhizosphere. D27, a cis–trans isomerase, catalyses the conversion of β-carotene

Methods

Results

Conclusion