Physiological And Molecular Mechanisms Of Tomato-Botrytis Cinerea Interactions Under Exogenous N-decanoyl-homoserine Lactone Application

Horticultural crops plants are facing diverse diseases since domestication period. Along with development of horticultural facilities, occurrence of the bacterial, viral and fungal diseases become prevalent and thereby causing serious economical loss. For instance, outbreak of Tobacco mosaic virus disease results in shorter plant height and shrinked yellow leaves; the bacterial disease (PstDC3000) also causes leaf yellowing and affects the quality and yield. Fungal diseases such as downy mildew and late blight, are very common and cause more loss especially under high temperature and high humidity in horticultural structures. So far, many researches indicate that fungal diseases affect many crop species such as rice, tomatoes and potatoes, and cause huge loss either at pre-or post-harvest stages. Botrytis cinerea is one of the necrotrophic fungi, commonly affect under low temperature and high moisture, and causes gray mold disease. To prevent and cure the Botrytis cinerea disease many measures have been practiced like pesticide application, grafting and cultivar screening. The widely used practice is pesticide application; however, it may cause environmental pollution and thus posing threat to sustainable environment. For these reasons, it is meaningful to research the bioactive factor which is environment friendly and effective on Botrytis cinerea. In this study we used Lycopersicum esculentum and Arabidopsis thaliana as plant material and studied the role of N-Decanoyl-DL-homoserine lactone (DHL) in plant immunity induction, In addition, we used automatically controlled growth chamber to make elevated CO2 environment and investigated the mechanism of the disease-resistance change and DHL effects in Lycopersicum esculentum under elevated CO2. The following are the major results:1、N-Decanoyl-DL-homoserine lactone confers resistance to fungal necrotizing pathogen Botrytis cinereaUnder normal atmospheric conditions, fully developed branches were treated with 60μM N-Decanoyl-DL-homoserine lactone (DHL), to study the changes in tomato- Botrytis cinerea interactions. The data suggest that DHL treatment inhibited fungal growth on leaf surfaces and the Botrytis cinerea actin expression, compared to the control, and the expression of the genes which related with JA signals pathway are sharply up regulated, while the gene related with SA signals pathway showed the opposite results. It can be concluded that DHL treatment renders enhanced resistance to Botrytis cinerea in Tomato leaves.2. N-Decanoyl-DL-homoserine lactone confers resistance to fungal necrotizing pathogen Botrytis cinereas and the effect rely on JA signalingTo test whether JA and SA signaling is involved in the resistance to necrotrophic fungal infection in Tomato leaves, we evaluated the responses of Tomato by the application of exogenous JA, S A and virus induced gene silencing(VIGS). The results show that JA and SA affect disease development caused by Botrytis cinerea in tomato, JA inhibited susceptibility to Botrytis cinerea through PⅡ & PⅠ Ⅱ and SA antagonised JA signaling pathway and NPR1 suppress the expression of the JA-dependent genes PI Ⅰ and PⅠ Ⅱ indicating that PⅠ Ⅰ and PⅠ Ⅱ are important for tomato resistance against Botrytis cinerea.Depend on the study of JA signal which is most important for tomato suppress fungal disease, then we go to study the signal mechanism of DHL effects. we used VIGS to study the signal mechanisms of DHL activated defense to resist pathogen. The results suggest that PⅠⅠ and PⅠⅡ are important for DHL-induced resistance to necrotrophic fungal pathogen Botrytis cinereas in tomato, and this resistance to Botrytis cinereas is involved in NPR1 regulated expression of PⅠⅠ and PⅠ Ⅱ genes. In a word, DHL-induced resistance to necrotrophic fungal pathogen Botrytis cinereas is involved in the antagonism between SA and JA.3. The effect and mechanism of N-Decanoyl-DL-homoserine lactone relieve Botrytis cinerea in Arabidopsis thalianaEnvironment change have a great impact on horticultural crops, so in this chapter we test whether the DHL-induced similar resistance to necrotrophic fungal infection in Arabidopsis leaves, we evaluated the responses of Arabidopsis JA-related mutants coronatine insensitive1 (coil-1), and the SA-related mutant non-expressed Pathogen Related1(npr1). These data indicate that DHL can also induce resistance to Botrytis cinerea in Arabidopsis and the induction of defense programs are involved in JA signaling pathway.4. The changes of elevated CO2 on tomato- Botrytis cinerea interactions and the effects of DHL on the resistance.Tomato showed more susceptibility to Botrytis cinerea under elevated CO2, but the stress can be relieved by DHL treatment. Under Botrytis cinerea inoculation, the expression of NPR1, PR1, PⅠ Ⅰ and PⅠ Ⅱ were higher, however the expression of PⅠⅠ and PⅠⅡ were limited by CO2, that may explain why tomato shows more susceptibility to Botrytis cinerea under elevated CO2. We also noticed that the expression of PⅠⅠ and PⅠⅡ can be induced by DHL treatment and thus tomato showed enhanced resistance to Botrytis cinerea.