| Tomato（Solanum lycopersicum）is an important economic crop globally.It is also a classic model for the study of plant immunity.More than 200 kinds of pathogens attack tomatoes and cause serious disease.Tomato gray leaf spot is caused by fungal pathogen Stemphylium spp.,which can infect a variety of crops.Tomato gray leaf spot emerges as a severe disease and causes great economic loss recently,because no stable resistance gene is available,and the plant immunity is unknown.Therefore,to reveal the disease-resistant mechanism is not only a high priority task for tomato production but also an important scientific issue.Toward understand the mechanism of plant resistance to gray leaf spot,we screened for resistant tomato lines.The results showed that the ABA-deficient mutant,sitiens,is highly resistant to gray leaf spot.In this study,we found that ABA could inhibit plant immunity and ABA biosynthesis inhibitor NDGA could be an efficient drug to prevent disease.First,compared to the susceptible background plant RR,sitiens showed increased resistance to gray leaf spot.Then,by measuring the reactive oxygen species（ROS）content,we found that,in sitiens,the content of superoxide anion（O2-）was higher than RR.It was also found that the hydrogen peroxide（H2O2）in sitiens was induced early compared to RR.The result indicates that the lack of ABA in sitiens increased content of reactive oxygen species in the early stage of infection.Using real-time quantitative PCR（q PCR）reaction,we detected the expression of genes related to salicylic acid（SA）and jasmonic acid（JA）signaling pathway in sitiens and RR after gray leaf spot infection.It was found that the induced expression of these genes in sitiens was significantly higher than that in RR.This proves that the resistance of sitiens is related to the high-level expression of related resistance genes mediated by SA and JA,and the presence of ABA inhibits the expression of genes mediated by SA and JA.Further we used ABA biosynthesis inhibitor NDGA that can increase tomato immunity to gray leaf spot and didn’t cause developmental defect.In summary,this study suggests that the defect of ABA in the sitiens mutant increased the accumulation of ROS in plants in the early stage of infection and transcription of SA and JA-mediated resistance genes.And application exogenous of ABA inhibitors can effectively enhance tomato resistance to gray leaf spot,which has great value for the prevention and control of gray leaf spot disease.In this study,we dissected the mechanism of disease resistance to gray leaf spot in sitiens and found a new method to enhance tomato disease resistance by ABA biosynthesis inhibitor NDGA. |
