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

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.

Citation
Iseki, M., Shida, K., Kuwabara, K., Wakabayashi, T., Mizutani, M., Takikawa, H., & Sugimoto, Y. (2017). Evidence for species-dependent biosynthetic pathways for converting carlactone to strigolactones in plants. Journal of Experimental Botany, 69(9), 2305–2318. doi:10.1093/jxb/erx428

Acknowledgements
This work was supported, in part, by grants from JICA/JST, the Science and Technology Research Partnership for Sustainable Development (SATREPS), and Grants-in-Aid for Scientific Research from the Ministry of Education, Science, Sports, and Culture of Japan (No. 25292065). The authors are grateful to Prof. Salim Al-Babili, King Abdullah University of Science and Technology, Kingdom of Saudi Arabia, for providing an authentic sample of CL. We also thank Prof. Abdel Gabar Babiker, National Center for Research, Sudan, for valuable discussions.

Publisher
Oxford University Press (OUP)

Journal
JOURNAL OF EXPERIMENTAL BOTANY

DOI
10.1093/jxb/erx428

PubMed ID
29294064

PubMed Central ID
PMC5913628

Additional Links
https://academic.oup.com/jxb/article/69/9/2305/4773904

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