9-cis-β-Apo-10ʹ-carotenal is the precursor of strigolactones in planta

Abstract

Main conclusion: 13C-isotope feeding experiments demonstrate that the apocarotenoid 9-cis-β-apo-10ʹ-carotenal is the precursor of several strigolactones in rice, providing a direct, in planta evidence for its role in strigolactone biosynthesis. Abstract: Strigolactones (SLs) are plant hormone that regulates plant architecture and mediates rhizospheric communications. Previous in vitro studies using heterogously produced enzymes unraveled the conversion of all-trans-β-carotene via the intermediate 9-cis-β-apo-10ʹ-carotenal into the SL precursor carlactone. However, a direct evidence for the formation of SLs from 9-cis-β-apo-10ʹ-carotenal is still missing. To provide this evidence, we supplied rice seedlings with 13C-labeled 9-cis-β-apo-10ʹ-carotenal and analyzed their SLs by LC–MS. Our results show that 9-cis-β-apo-10ʹ-carotenal is the SL precursor in planta and reveal, for the first time, the application of labeled long-chain apocarotenoids as a promising approach to investigate apocarotenoid metabolism and the genesis of carotenoid-derived growth regulators and signaling molecules.