Recruitment of distinct UDP‐glycosyltransferase families demonstrates dynamic evolution of chemical defense within Eucalyptus L'Hér

Abstract

Summary The economic and ecologically important genus Eucalyptus is rich in structurally diverse specialized metabolites. While some specialized metabolite classes are highly prevalent across the genus, the cyanogenic glucoside prunasin is only produced by c. 3% of species. To investigate the evolutionary mechanisms behind prunasin biosynthesis in Eucalyptus, we compared de novo assembled transcriptomes, together with online resources between cyanogenic and acyanogenic species. Identified genes were characterized in vivo and in vitro. Pathway characterization of cyanogenic Eucalyptus camphora and Eucalyptus yarraensis showed for the first time that the final glucosylation step from mandelonitrile to prunasin is catalyzed by a novel UDP‐glucosyltransferase UGT87. This step is typically catalyzed by a member of the UGT85 family, including in Eucalyptus cladocalyx. The upstream conversion of phenylalanine to mandelonitrile is catalyzed by three cytochrome P450 (CYP) enzymes from the CYP79, CYP706, and CYP71 families, as previously shown. Analysis of acyanogenic Eucalyptus species revealed the loss of different ortholog prunasin biosynthetic genes. The recruitment of UGTs from different families for prunasin biosynthesis in Eucalyptus demonstrates important pathway heterogeneities and unprecedented dynamic pathway evolution of chemical defense within a single genus. Overall, this study provides relevant insights into the tremendous adaptability of these long‐lived trees.

Identification of a Unique Genomic Region in Sweet Chestnut (Castanea sativa Mill.) That Controls Resistance to Asian Chestnut Gall Wasp Dryocosmus kuriphilus Yasumatsu

“…Interestingly, cyanogenic glucoside biosynthesis requires two cytochrome P450 enzymes and a UDP-glucosyltransferase, which are the genes identified in the MGC of our genomic region of interest. Indeed, MGCs for cyanogenic glucoside biosynthesis found in Lotus japonicus, Sorgum bicolor, and Manihot esculenta contain CYP genes belonging to the clan CYP71 and UDP-glucosyltransferase UGT85 genes [53], while in Eucalyptus, a cyanogenic glucoside MGC contains a novel UDP-glucosyltransferase of class UGT87, similar to the C. sativa UGT identified in our study [54]. We hypothesize that the putative MGC of our study is involved in the production of a metabolite needing glycosylation, maybe in the biosynthesis of a cyanogenic glucoside.…”

Comparative Functional Characterization of LuUGT74S1 from Linum usitatissimum L. and Its Closed Homologues from Fragaria vesca Subsp. vesca and Camellia sinensis

“…Since SECO-glucosides have been detected in both the tea plant and strawberries, other proteins less closely related to LuUGT74S1 must be responsible for the formation of the lignan glucosides in these plants. Consequently, this indicates a convergent evolution of the lignan UGTs similar to the UGTs involved in the formation of cyanogenic glucosides . The uniqueness and specificity of the catalytic activity of LuUGT74S1 are further supported by the fact that homozygous flax lines LuUGT74S1-nonsense mutants were unable to produce SDG .…”

“…Consequently, this indicates a convergent evolution of the lignan UGTs similar to the UGTs involved in the formation of cyanogenic glucosides. 46 The uniqueness and specificity of the catalytic activity of LuUGT74S1 are further supported by the fact that homozygous flax lines LuUGT74S1-nonsense mutants were unable to produce SDG. 34 This proves that LuUGT74S1 is the only enzyme in flax that catalyzes the formation of SDG from SECO.…”

Exploring the Evolvability of Plant Specialized Metabolism: Uniqueness Out Of Uniformity and Uniqueness Behind Uniformity

“…The exceptional reactions specifically catalyzed by CYP736 in Lotus and CYP706 and UGT87 in Eucalyptus , respectively, which are apparently lineage-specific recruited enzymes ( Takos et al. 2011 , Hansen et al. 2022 ), support the parallel evolution of common metabolisms.…”