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-beta-carotene via the intermediate 9-cis-beta-apo-10'-carotenal into the SL precursor carlactone. However, a direct evidence for the formation of SLs from 9-cis-beta-apo-10'-carotenal is still missing. To provide this evidence, we supplied rice seedlings with C-13-labeled 9-cis-beta-apo-10'-carotenal and analyzed their SLs by LC-MS. Our results show that 9-cis-beta-apo-10'-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.