Role of THT and Twi on the volatilome profile of tomato plants upon wounding

In response to stress situations, such as wounding, plants trigger the release of a series of volatile organic compounds (VOCs), which play a fundamental role in their defense, including the plant communication. In addition, the accumulation of hydroxycinnamic acid amides (HCAAs) and flavonoids in response to stress was observed. The last stage of HCAA biosynthesis involves the activity of the enzyme tyramine hydroxycinnamoyl transferase (THT) (Zacarés et al., 2007). Moreover, most flavonoids can accumulate in the form of glycoconjugates, by the action of glycosyltransferases. In particular, Twi1 glycosyltransferase show in vitro activity toward the flavonoids quercetin and kaempferol. Both THT and Twi1 are involved in plant defensive mechanisms against pathogens, since tomato plants that overexpress THT (35S:THT) are more resistant to the bacterium Pseudomonas syringae (Campos et al., 2014), while tomato plants that silence Twi1 (RNAi_Twi1) are more susceptible to the Tomato spotted wilt virus (Campos et al., 2019). Both genes, THT and Twi1, are induced in tomato plants in response to wounding, although their role in this type of stress has not been studied in detail to date.

To study the possible role of THT and Twi in plant communication, a metabolomic study was carried out to determine the volatilome induced by the mechanical wounding of both transgenic tomato lines 35S:THT and RNAi_Twi1.

This research provides evidence that the mechanical wounding of 35S:THT or RNAi_Twi1 transgenic plants leads to differential effects on the metabolomic profiles of VOCs, suggesting that THT and Twi could play a role in plant communication. Specifically, we identified that some volatiles, such as (Z)-3-Hexenyl butyrate, (E)-2-hexenal, and (Z)-3-hexen-1-ol, show significant variations in their emission after being wounded in transgenic tomato plants.