byYanxia Zhang, Aalt D J Van Dijk, Adrian Scaffidi, Gavin R Flematti, Manuel Hofmann, Tatsiana Charnikhova, Francel Verstappen, Jo Hepworth, Sander Van Der Krol, Ottoline Leyser, Steven M Smith, Binne Zwanenburg, Salim Al-Babili, Harro J Bouwmeester
Yanxia Zhang, Aalt D J van Dijk, Adrian Scaffidi, Gavin R Flematti, Manuel Hofmann, Tatsiana Charnikhova, Francel Verstappen, Jo Hepworth, Sander van der Krol, Ottoline Leyser, Steven M Smith, Binne Zwanenburg, Salim Al-Babili, Carolien Ruyter-Spira & Harro J Bouwmeester. Rice cytochrome P450 MAX1 homologs catalyze distinct steps in strigolactone biosynthesis. Nature Chemical Biology. doi:10.1038/nchembio.1660
Strigolactones (SLs) are a class of phytohormones and rhizosphere signaling compounds with high structural diversity. Three enzymes, carotenoid isomerase DWARF27 and carotenoid cleavage dioxygenases CCD7 and CCD8, were previously shown to convert all-trans-β-caroteneto carlactone (CL), the SL precursor. However, how CL is metabolized to SLs has remained elusive. Here, by reconstituting the SL biosynthetic pathway in Nicotiana benthamiana, we show that a rice homolog of Arabidopsis MORE AXILLARY GROWTH 1 (MAX1), encodes a cytochrome P450 CYP711 subfamily member that acts as a CL oxidase to stereoselectively convert CL into ent-2′-epi-5-deoxystrigol (B-C lactone ring formation), the presumed precursor of rice SLs. A protein encoded by a second rice MAX1 homolog then catalyzes the conversion ofent-2′-epi-5-deoxystrigol to orobanchol. We therefore report that two members of CYP711 enzymes can catalyze two distinct steps in SL biosynthesis, identifying the first enzymes involved in B-C ring closure and a subsequent structural diversification step of SLs.