CYP76C1 (Cytochrome P450)-Mediated Linalool Metabolism and the Formation of Volatile and Soluble Linalool Oxides in Arabidopsis Flowers: A Strategy for Defense against Floral Antagonists

Abstract

The acyclic monoterpene alcohol linalool is one of the most frequently encountered volatile compounds in floral scents. Various linalool oxides are usually emitted along with linalool, some of which are cyclic, such as the furanoid lilac compounds. Recent work has revealed the coexistence of two flower-expressed linalool synthases that produce the (S)-or (R)-linalool enantiomers and the involvement of two P450 enzymes in the linalool oxidation in the flowers of Arabidopsis thaliana. Partially redundant enzymes may also contribute to floral linalool metabolism. Here, we provide evidence that CYP76C1 is a multifunctional enzyme that catalyzes a cascade of oxidation reactions and is the major linalool metabolizing oxygenase in Arabidopsis flowers. Based on the activity of the recombinant enzyme and mutant analyses, we demonstrate its prominent role in the formation of most of the linalool oxides identified in vivo, both as volatiles and soluble conjugated compounds, including 8-hydroxy, 8-oxo, and 8-COOH-linalool, as well as lilac aldehydes and alcohols. Analysis of insect behavior on CYP76C1 mutants and in response to linalool and its oxygenated derivatives demonstrates that CYP76C1-dependent modulation of linalool emission and production of linalool oxides contribute to reduced floral attraction and favor protection against visitors and pests.

Green tea flavour determinants and their changes over manufacturing processes

“…Reduced levels of the two monoterpenols may be a consequence of substantial inhibition of enzymatic glycoside hydrolysis, due to heat inactivation of the corresponding enzymes during manufacture. Additionally, reduced levels in product tea infusions may also result from its conversion to stress-induced linalool oxides, which may be catalysed by CYP76C1 as shown in Arabidopsis (Boachon et al, 2015). Linalool and its derivatives (Matich, Bunn, & Hunt, 2010) with strong floral scents are key contributors for tea floral scent based on OAV analysis, and changes in their abundances most likely altered the tea aromas, as found by Takeo (1981).…”

More lessons from linalool: insights gained from a ubiquitous floral volatile

“…Both enantiomers of linalool (synthesized in plastids) are oxidized by two cytochrome P450 enzymes (CYP71B31 and CYP76C3, located in the endoplasmic reticulum) into several isomers of hydroxy-and epoxylinalool, some of which are converted to non-volatile conjugates [10]. Subsequent experiments revealed another p450 (CYP76C1) with high expression in floral tissues and the capacity to progressively oxidize the C-8 position of linalool to alcohol, aldehyde and acid forms, and (presumably through a furanoid intermediate) to lilac alcohols and aldehydes [17 ]. Why would an autogamous plant invest in such complex metabolism of a common floral VOC?…”

“…Blue arrows represent biosynthetic transformation, green arrows indicate attraction and red piston-ended lines indicate repellence. (a) Attraction of specialized pollinators (noctuid moths, long tongued fungus gnats -and repellence of short tongued gnats) by lilac compounds [14,16 ], (b) attraction of generalized pollinators (bees, butterflies) by linalool [42], (c) (hypothesized) exclusion of ants [42] and yeasts [40] by linalool solved in nectar, (d, e) repellence of facultative visitors to Arabidopsis thaliana flowers by lilac compounds and attraction of same by linalool [17 ]. (f) Decreasing dependence upon pollinators to effect reproductive success, from a nectarbearing allogamous flower on the left (e.g.…”

Metabolic Products of Linalool and Modulation of GABAA Receptors

“…After administration of lavender oil, the main constituent linalool is exposed to enzymatic activity of cytochrome P-450 (CYP76C1) in lung and liver (Chadha and Madyastha, 1984; Boachon et al, 2015). Linalool derivatives such as 8-oxolinalool, 8-hydroxylinalool, and 8-carboxylinalool are formed (Aprotosoaie et al, 2014).…”