Oximes: Unrecognized Chameleons in General and Specialized Plant Metabolism

Abstract

Oximes (RRC=NOH) are nitrogen-containing chemical constituents that are formed in species representing all kingdoms of life. In plants, oximes are positioned at important metabolic bifurcation points between general and specialized metabolism. The majority of plant oximes are amino acid-derived metabolites formed by the action of a cytochrome P450 from the CYP79 family. Auxin, cyanogenic glucosides, glucosinolates, and a number of other bioactive specialized metabolites including volatiles are produced from oximes. Oximes with the E configuration have high biological activity compared with Z-oximes. Oximes or their derivatives have been demonstrated or proposed to play roles in growth regulation, plant defense, pollinator attraction, and plant communication with the surrounding environment. In addition, oxime-derived products may serve as quenchers of reactive oxygen species and storage compounds for reduced nitrogen that may be released on demand by the activation of endogenous turnover pathways. As highly bioactive molecules, chemically synthesized oximes have found versatile uses in many sectors of society, especially in the agro- and medical sectors. This review provides an update on the structural diversity, occurrence, and biosynthesis of oximes in plants and discusses their role as key players in plant general and specialized metabolism.

Glucosinolate and phenylpropanoid biosynthesis are linked by proteasome-dependent degradation of PAL

“…It appears that the accumulation of aldoximes or their derivatives limits phenylpropanoid production (Hemm et al, 2003;Kim et al, 2015). Because aldoximes are precursors of many other biomolecules besides glucosinolates, including cyanogenic glucosides and nitriles, and can be found in diverse plant species such as maize, poplar, yew and coca (Irmisch et al, 2013(Irmisch et al, , 2015Luck et al, 2017;Sørensen et al, 2018;Bhalla et al, 2018;Dhandapani et al, 2019), aldoxime-mediated suppression of phenylpropanoid metabolism may be relevant to other species and metabolic pathways beyond Arabidopsis.…”

Unrivalled diversity: the many roles and reactions of bacterial cytochromes P450 in secondary metabolism

“…281 Heteroatom oxidation by P450 enzymes has been widely reported, 12 and although such reactions are oen found in xenobiotic metabolism, NocL serves as an important reminder that the role of P450s in heteroatom oxidation during secondary metabolism cannot be discounted.…”

Glucosinolate and phenylpropanoid biosynthesis are linked by proteasome‐dependent degradation of PAL

“…Because aldoximes are precursors of many other biomolecules besides glucosinolates, including cyanogenic glucosides and nitriles, and can be found in diverse plant species such as maize, poplar, yew and coca (Irmisch et al, 2013(Irmisch et al, , 2015Luck et al, 2017;Bhalla et al, 2018;Sørensen et al, 2018;Dhandapani et al, 2019), aldoxime-mediated suppression of phenylpropanoid metabolism may be relevant to other species and metabolic pathways beyond Arabidopsis. Previous work showed that glucosinolate/phenylpropanoid crosstalk requires MED5 (Kim et al, 2015), but its underlying mechanism was not identified.…”

“…In summary, our transcriptome analyses and genetic study with a set of glucosinolate-deficient mutants reveal that the accumulation of aldoximes or their derivatives affects expression of a specific group of F-box genes, thereby altering the stability of PAL, as well as acting to negatively affect at least one other step of phenylpropanoid metabolism. Considering that aldoximes are precursors of important biomolecules and that the oxime-producing CYP79s are widespread in higher plants (Sørensen et al, 2018), this crosstalk may be relevant not only to glucosinolates but also to other metabolic pathways.…”