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 Related to the defensive phytohormone SA, our aim also arises from some unpublished results in our group on the role of a putative salicylate 5-hydroxylase (Sl S5H) that hydroxylates SA (2-hydroxybenzoic acid) into gentisic acid (GA,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.植物胁迫造成的经济损失，以及公众对环境可持续性的关注度日益提升，凸显出开发新型农业策略的必要性。筛选可作为防御反应诱导剂、参与植物防御信号通路的天然化合物，正是此类策略之一。 为此，I2Tom.Com项目旨在研究番茄抵御细菌的防御信号通路：该通路既会在植株受感染后通过产生移动信号激活（即植株内通讯（Intra-plant Communication）），也会通过受感染的发射植株（emitting plants, e-plants）释放的挥发性信号，由邻近的接收植株（receiving plants, r-plants）感知而激活（即植株间通讯（Inter-plant Communication））。 具体而言，本项目将探究三类参与番茄抗细菌防御反应的分子在上述信号通路中的作用，包括苯系物类的水杨酸（salicylic acid, SA）及其甲酯（methyl ester, MeSA）、羟基化单萜类物质，以及绿叶挥发物（green leaf volatiles, GLVs）酯类。 本项目的研究基础为：我们已鉴定出可有效抵御细菌感染的番茄植株所差异化释放的挥发性有机化合物（volatile organic compounds, VOCs），其中包括GLVs酯类与羟基化单萜类物质。此外，我们还证实了Z-3-己烯基丁酸酯（Z-3-hexenyl butyrate, HB）的防御功能：作为一种GLVs酯类，它因具备诱导气孔关闭的卓越能力而获得专利并完成授权，可在农业领域实现多种应用（Lison等，2017；Lopez-Gresa等，2018；Paya等，2020）。 此外，羟基化单萜类物质防御功能的部分预实验结果已被纳入支撑本项目的前沿研究成果中，进一步佐证了本项目的合理性。针对防御性植物激素SA，我们的研究目标还源于团队尚未发表的相关成果：一种推定的水杨酸5-羟化酶（salicylate 5-hydroxylase, SlS5H）可将SA（即2-羟基苯甲酸）羟化为龙胆酸（GA，2,5-二羟基苯甲酸）。我们已观察到，沉默SlS5H基因可显著提升番茄植株的抗细菌能力，这凸显了SA分解代谢在植物防御信号通路中的重要性。由于SA可被甲基化为挥发性形式MeSA，此类转基因植株将成为极佳的研究工具，用于探究该酚类化合物在植株内及植株间抵御细菌或其他病原体的防御通讯中所发挥的作用。 另一方面，我们团队近期揭示了核糖体应激作为类病毒致病机理的新维度（Cottilli等，2019；Prol等，2020）。因此，本项目还将探究此类转基因植株在感染类病毒时的核糖体应激现象。 总体而言，I2Tom.Com项目旨在通过以下两类材料的表型、分子与化学特征分析，探究三类化合物在番茄防御反应中的作用：(i) 上述防御信号合成发生改变的转基因发射植株（e-plants）；(ii) 分别与/不与特异性释放抗病挥发性信号的发射植株共培养的接收植株（r-plants）。 本项目将助力解析植物防御信号通路，通过筛选新型天然诱导剂并培育过量释放此类信号的转基因植株，为农业领域抵御生物胁迫开发新的生物技术解决方案。