In vivo characterization of key iridoid biosynthesis pathway genes in catnip (Nepeta cataria)

Abstract

Main conclusion Using virus-induced gene silencing, we demonstrated that the enzymes GES, ISY, and MLPL are responsible for nepetalactone biosynthesis in Nepeta cataria. Abstract Nepetalactone is the main iridoid that is found in the Nepeta genus and is well-known for its psychoactive effect on house cats. Moreover, there is a burgeoning interest into the effect of nepetalactone on insects. Although the enzymes for nepetalactone biosynthesis have been biochemically assayed in vitro, validation of the role that these enzymes have in planta has not been demonstrated. Virus-induced gene silencing (VIGS) is a silencing method that relies on transient transformation and is an approach that has been particularly successful when applied to a variety of non-model plants. Here, we use a recently designed visual-marker dependent VIGS system to demonstrate that the nepetalactone biosynthetic enzymes GES, ISY, and MLPL impact nepetalactone biosynthesis in Nepeta cataria.

Functional iridoid synthases from iridoid producing and non-producing Nepeta species (subfam. Nepetoidae, fam. Lamiaceae)

“…The reaction catalyzed by GES is considered a key gatekeeping step in iridoid biosynthesis, since this enzyme is responsible for diverting metabolic flux away from canonical monoterpenes by converting GPP to geraniol, the precursor of iridoids ( Boachon et al., 2018 ). Silencing of GES in N. cataria leaves resulted in significant decrease of the content of all nepetalactoneL isomers and 1,5,9- epi deoxyloganic acid ( Palmer et al., 2022 ), while in C. roseus the content of iridoid-derived alkaloids was decreased ( Kumar et al., 2015 ). As NEPS and MLPL work in combination with ISY to control the stereochemical mode of 8-oxogeranial cyclization ( Lichman et al., 2020 ), it might be speculated that besides GES, functional ISY and some of the NEPSs are important missing parts to complete the iridoid biosynthesis puzzle in this species.…”

Chemical Composition and Anti-Candida Activity of Mentha suaveolens Ehrh. Essential Oils Obtained by Different Distillation Processes

“…Along with glycosylated iridoids, nepetalactones are found in many Lamiaceae species, the most common source being Nepeta cataria L. (catnip), which is known for its felineattracting properties [36]. These lactones are produced via a monoterpenoid pathway involving several oxidation processes on geraniol and a two-step enzyme-controlled cyclization leading to the formation of specific stereoisomers [36][37][38][39]. Mentha species are not considered to be an important source of nepetalactones; they are usually present in traces or low amounts in their EOs [40].…”