Gene Coexpression Analysis Reveals Complex Metabolism of the Monoterpene Alcohol Linalool inArabidopsisFlowers  

Abstract

The cytochrome P450 family encompasses the largest family of enzymes in plant metabolism, and the functions of many of its members in Arabidopsis thaliana are still unknown. Gene coexpression analysis pointed to two P450s that were coexpressed with two monoterpene synthases in flowers and were thus predicted to be involved in monoterpenoid metabolism. We show that all four selected genes, the two terpene synthases (TPS10 and TPS14) and the two cytochrome P450s (CYP71B31 and CYP76C3), are simultaneously expressed at anthesis, mainly in upper anther filaments and in petals. Upon transient expression in Nicotiana benthamiana, the TPS enzymes colocalize in vesicular structures associated with the plastid surface, whereas the P450 proteins were detected in the endoplasmic reticulum. Whether they were expressed in Saccharomyces cerevisiae or in N. benthamiana, the TPS enzymes formed two different enantiomers of linalool: (2)-(R)-linalool for TPS10 and (+)-(S)-linalool for TPS14. Both P450 enzymes metabolize the two linalool enantiomers to form different but overlapping sets of hydroxylated or epoxidized products. These oxygenated products are not emitted into the floral headspace, but accumulate in floral tissues as further converted or conjugated metabolites. This work reveals complex linalool metabolism in Arabidopsis flowers, the ecological role of which remains to be determined.

Dual Function of the Cytochrome P450 CYP76 Family from Arabidopsis thaliana in the Metabolism of Monoterpenols and Phenylurea Herbicides

“…Conversely, CYP76C1 and CYP76B6 very actively catalyzed the oxidation of several tested compounds. CYP76C1 was the most active with linalool, the only monoterpenol for which oxidation products were thus far reported to be emitted by A. thaliana (Rohloff and Bones, 2005) and detected as soluble conjugates (Aharoni et al, 2003;Ginglinger et al, 2013). Moreover, linalool synthases were previously shown to be essentially expressed in A. thaliana flowers, the main site of expression of CYP76C1 .…”

“…Although extensive monoterpenol (especially linalool) oxidative metabolism has been described in many plant species, leading to fragrant and bioactive compounds as diverse as alcohols, aldehydes, acids, and epoxides (Williams et al, 1982;Matich et al, 2003Matich et al, , 2011Luan et al, 2005Luan et al, , 2006Ginglinger et al, 2013), pyranoid or furanoid linalool derivatives (Pichersky et al, 1994;Raguso and Pichersky, 1999), and geraniol-derived iridoids and secoiridoids (Dinda et al, 2007a(Dinda et al, , 2007b(Dinda et al, , 2011Tundis et al, 2008), limited information is available on the enzymes generating these oxygenated compounds. Involvement of a cytochrome P450 (P450) enzyme extracted from Vinca rosea (now renamed Catharanthus roseus) in the hydroxylation of geraniol and nerol was suggested as early as 1976 (Madyastha et al, 1976).…”

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

“…Linalool and its oxides have been reported to accumulate as free or conjugated compounds in flower tissues from various plant species including Arabidopsis (Aharoni et al, 2003;Ginglinger et al, 2013;Yang et al, 2013). Soluble linalool derivatives were thus quantified by targeted UPLC-MS/MS in the inflorescence of wild-type, cyp76c1, and complemented/35S:CYP76C1 lines ( Figure 6; Supplemental Figure 10).…”

Illuminating a plant’s tissue-specific metabolic diversity using computational metabolomics and information theory

“…Tissue-level PCC coexpression analysis among genes and metabolites has traditionally been shown to be an efficient way forward for gene function analysis in secondary metabolism (6,44,46,47). However, one important message of the present study is that because PCC-based coexpression analysis relies on trends inferred from gene/metabolite expression levels, certain tissue-level genemetabolite associations are difficult to capture via this approach because they take place only in a few of the analyzed tissues, thereby resulting in a poor coexpression output.…”