Authors:

Justin Ray Walder

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Terpenoids are a large class of secondary metabolites with important roles in plant defense, growth, and development. These compounds are responsible for pigment formation, flavor development, aroma, and nutritional value in crops. Most tomato varieties have been traditionally bred for traits improving size, pest resistance, and storage, yet have decreased terpenoid levels. Terpenoids are synthesized from the mevalonic acid (MVA) and methylerythritol phosphate (MEP) pathways. Exchanges of pathway intermediates occur to control flux toward different terpenoids such as lycopene, carotenoids, sterols, ubiquinone, phylloquinone, etc. We hypothesized that targeted over-expression of rate-limiting pathway enzymes could increase levels of terpenoids by increasing the pool size of pathway intermediates. We used transient Agro-infiltration in tomato fruits to over-express key enzymes (AtHMGR- 2A-PMK, AtIPK, and RcGFPPS1) of the MVA pathway. We tested our strategy of over-expressing these genes individually and in combination to observe potential additive effects on terpenoid biosynthesis. Since there is crosstalk between the pathways, we measured metabolites, which are predominantly derived from one pathway or the other, such as lycopene, ?-carotene, and phytoene from the MEP pathway, and sterols and ubiquinone from the MVA pathway. Upon analysis, we observed a significant increase in the levels of lycopene, sterols, and ubiquinone in tomato fruits at Br+10 stages. These observations suggest that over- expression of the above genes is responsible for increased levels of MVA intermediate pools and their effective shuttling across the MEP pathway. Based on our transient transformation results in tomato fruit, we expect to see increased terpenoid production in transformed stable lines. Keywords: Terpenoids; MVA Pathway; Agro-Infiltration; Tomato; Over-Expression † Presenting Undergrad Author; ‡ Contributing Undergrad Author; * Undergrad Acknowledgment

Source:

Purdue University / 2025

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Co-authors:

Justin Ray Walder