Direct conversion of carlactonoic acid to orobanchol by cytochrome P450 CYP722C in strigolactone biosynthesis

Abstract

Strigolactones (SLs) are carotenoid-derived phytohormones and rhizosphere signaling molecules for arbuscular mycorrhizal fungi and root parasitic weeds. Why and how plants produce diverse SLs are unknown. Here, cytochrome P450 CYP722C is identified as a key enzyme that catalyzes the reaction of BC-ring closure leading to orobanchol, the most prevalent canonical SL. The direct conversion of carlactonoic acid to orobanchol without passing through 4-deoxyorobanchol is catalyzed by the recombinant enzyme. By knocking out the gene in tomato plants, orobanchol was undetectable in the root exudates, whereas the architecture of the knockout and wild-type plants was comparable. These findings add to our understanding of the function of the diverse SLs in plants and suggest the potential of these compounds to generate crops with greater resistance to infection by noxious root parasitic weeds.

Hydroxyl carlactone derivatives are predominant strigolactones in Arabidopsis

“…We will continue to search for any candidate compounds that are likely to be derived from 1'-HO-MeCLA from atd14 mutants. LBO was uncovered from transcriptomics (Brewer et al, 2016), and similar methods recently led to the discovery that CYP722C from cowpea and tomato converts CLA directly to orobanchol (Wakabayashi et al, 2019) and that a 2-oxoglutarate-dependent dioxygenase (2-OGD) from a nearby clade to LBO is involved in SL biosynthesis in Lotus japonicus (Mori, Nomura, & Akiyama, 2020). We will continue reverse genetic and mass spectrometric approaches to find related SL biosynthetic genes and shoot branching inhibitors.…”

Recent progress in the chemistry and biochemistry of strigolactones

“…46) Recently, another clade of cytochrome P450 CYP722C functioning downstream of MAX1 was shown to directly convert CLA to orobanchol, presumably via 18-HO-CLA, although formation of the B/C ring structure with the recombinant enzyme was not stereoselective. 47) In birdsfoot trefoil (Lotus japonicus), 18-HO-CLA has been detected as an endogenous compound 48) and also in other plant species (K. Yoneyama, unpublished data). These results clearly indicate that the biosynthesis from β-carotene to CLA is a common pathway for SLs but further steps after formation of CLA may differ with each plant species and thus with each SL.…”

“…The possibility that BIHs are not canonical SLs is further supported by the observation that targeted mutation in SICYP722C, a gene responsible for the conversion of CLA to orobanchol in tomato, resulted in a significant reduction in germination stimulation activity of root exudates due to blockage of orobanchol biosynthesis but did not show the apparent phenotypes of the SL-deficient mutant Slccd8. 47) When the root parasitic plants evolved around 40-60 million years ago, 98,99) SLs already existed in the rhizosphere as the host signals for AM fungi 100) with which land plants established symbiotic relationships 460 million years ago. [100][101][102][103] It is likely that SLs evolved 750-1200 million years ago.…”

Hydroxyl carlactone derivatives are predominant strigolactones inArabidopsis

“…However, we cannot yet find any candidate compounds that are likely to be derived from 1’-HO-MeCLA from atd14 mutants (data not shown). LBO was uncovered from transcriptomics (Brewer et al 2016) and similar methods recently led to the discovery that CYP722C from cowpea and tomato converts CLA directly to orobanchol (Wakabayashi et al 2019), and that a 2-oxoglutarate dependent dioxygenase (2-OGD) from a nearby clade to LBO is involved in SL biosynthesis in Lotus japonicus (Mori et al 2020). We will continue reverse genetic and mass spectrometric approaches to find related SL biosynthetic genes and shoot branching inhibitors.…”