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Elucidation of ustilaginoidin biosynthesis reveals a previously unrecognised class of ene-reductases† † Electronic supplementary information (ESI) available: including all experimental and spectroscopic details. See DOI: 10.1039/d1sc02666f

ABSTRACT: Ustilaginoidins are a type of mycotoxin featuring a dimeric naphtho-γ-pyrone skeleton, produced by the rice false smut pathogen Ustilaginoidea virens. Here we used gene disruption, heterologous expression in Aspergillus oryzae, feeding experiments, and in vitro experiments to fully elucidate the biosynthesis of ustilaginoidins. A new route to dimeric 2,3-unsaturated naphtho-γ-pyrones via dimerization of YWA1 (and 3-methyl YWA1) followed by dehydration was discovered. Intriguingly, the reduction of the 2,3-double bond of the pyrenone ring was catalyzed by a phospholipid methyltransferase-like enzyme (UsgR). The reductase was specific for reduction of monomeric, linear naphtho-γ-pyrenones, but not for the dimers. Atroposelective coupling of various monomers by the laccase (UsgL) led to diverse ustilaginoidins. Moreover, 3-epimerism of the 3-methyl-2,3-dihydro-naphtho-γ-pyrones adds additional complexity to the biosynthesis. The 2,3-double bond reduction of the pyrenone ring in linear naphtho-γ-pyrenones was catalyzed by a phospholipid methyltransferase-like enzyme, namely UsgR, which is a previously unrecognised class of ene-reductases.

SUBMITTER: Xu D

PROVIDER: S-EPMC8597850 | biostudies-literature |

REPOSITORIES: biostudies-literature

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