Effects of application of (Z)-3-Hexenol on Solanum lycopersicum

The economic losses caused by plant stresses and the greater awareness of the environment sustainability make evident the need to develop new agricultural strategies. The identification of natural compounds participating in the plant defence signalling that can be used as inducers of the defensive response constitutes one of these strategies. To this purpose, I2Tom.Com aims to study the Tomato signalling defence response against bacteria which is activated both within the plant upon infection, through the production of mobile signals (Intra-plant Communication), and in the neighbouring plants, through the perception by the receiving plants (r-plants) of volatile signals released by infected emitting plants (e-plants; Inter-plant Communication). Particularly, we will explore the involvement in these signalling mechanisms of three groups of molecules participating in the tomato response against bacteria, including the benzenoids salicylic acid (SA) and its methyl-ester (MeSA), hydroxylated monoterpenoids, and esters of green leaf volatiles (GLVs). Our proposal is based on our results on the identification of volatile organic compounds (VOCs) differentially emitted by tomato plants that effectively resist the bacterial infection, including esters of GLVs and hydroxylated monoterpenoids. We have also demonstrated the defensive role for a Z-3-hexenyl butyrate (HB), a GLV ester that has been patented and licenced because of its extraordinary capacity to induce the stomata closure, displaying multiple uses in agriculture (Lison et al., 2017; Lopez-Gresa et al, 2018; Paya et al., 2020). Besides, some preliminary results on the defensive role of hydroxylated monoterpenoids are included in the state of the art support our proposal. Related to the defensive phytohormone SA, our aim also arises from some unpublished results in our group on the role of a putative salicylate 5-hydroxylase (Sl S5H) that hydroxylates SA (2-hydroxybenzoic acid) into gentisic acid (GA, 2,5-dihydroxybenzoic acid). We have observed that silencing Sl_S5H noticeably enhances resistance to bacteria in tomato plants, pointing out the importance of SA catabolism in the plant signalling response. Since SA can be methylated into the volatile form MeSA, these transgenic plants constitute an excellent tool to study the role of this phenolic compound not only in the intra- but also in the inter-plant defensive communication against bacteria or other pathogens. On the other hand, our group has recently unravelled the ribosomal stress as a new dimension of the viroid pathogenesis (Cottilli et al, 2019; Prol et al., 2020). Therefore, this phenomenon will also be explored in these transgenic plants upon viroid infection. Mostly, I2Tom.Com aims to study the role of three families of compounds on the tomato defence response through the phenotypical, molecular and chemical characterization of: (i) transgenic e-plants with alterations in the production of any of these defensive signals, and (ii) r-plants grown in the presence or absence of these e-plants specifically emitting different aromas for resistance. Our proposal will help understand the plant signalling defence response that could lead to the development of new biotechnological alternatives to combat biotic stresses in agriculture, through the identification of new natural inducers and the generation of transgenic plants over-emitting them.