# Genomic Identification and Biochemical Characterization of Methyl Jasmonate (MJ)-Inducible Terpene Synthase Genes in Lettuce (Lactuca sativa L. cv. Salinas)

## TL;DR

This study identifies and characterizes genes in lettuce responsible for producing terpenes when triggered by methyl jasmonate, revealing key insights into their regulation and function.

## Contribution

The first comprehensive framework for MJ-induced terpene biosynthesis in lettuce, including functional characterization of multiple terpene synthase genes.

## Key findings

- MJ elicitation triggered the production of a terpene blend dominated by (E)-β-ocimene, (E)-β-caryophyllene, and caryophyllene oxide.
- 17 MJ-responsive LsTPS genes were identified, with some showing over 20,000-fold induction.
- Six recombinant LsTPS enzymes were functionally characterized, revealing diverse terpene synthase activities.

## Abstract

Terpenes are diverse plant metabolites with essential ecological and physiological functions, yet their biosynthetic regulation in lettuce (Lactuca sativa L.) remains poorly understood. By integrating volatile profiling, genome-wide identification, and biochemical characterization of terpene synthase (TPS) genes, we elucidated how methyl jasmonate (MJ) induces terpene formation in lettuce seedlings. Headspace analysis of 10-day-old seedlings revealed that while mock-treated tissues emitted no detectable volatiles, MJ elicitation triggered the de novo production of a terpene blend dominated by (E)-β-ocimene (9.3–14.6%), (E)-β-caryophyllene (37.2–46.9%), and caryophyllene oxide (26.2–41.4%). A genome-wide search identified 54 putative LsTPS genes, often clustered with prenyl transferases or cytochrome P450 genes. Gene expression assays revealed 17 MJ-responsive LsTPS genes; among them, LsTPS21, LsTPS23, LsTPS28, LsTPS51, and LsTPS52 showed strong (>200-fold) induction, with LsTPS52 exceeding a 20,000-fold increase. Functional characterization of six recombinant enzymes demonstrated diverse substrate specificities: LsTPS8 as an α-copaene synthase, LsTPS16 as a linalool synthase, LsTPS24 as an (E)-nerolidol synthase, LsTPS21 and LsTPS23 as (E)-β-ocimene synthases, and LsTPS10 as an (E)-β-caryophyllene synthase. Phylogenetic analyses confirmed conserved domains characteristic of the TPS-a and TPS-b subfamilies. This study presents the first comprehensive framework for MJ-induced terpene biosynthesis in lettuce, offering new insights into Asteraceae terpenoid metabolism.