Pepper mild mottle virus (PMMoV), an RNA virus, is one of the most devastating pathogens in pepper crops and has a significant influence on global crop yields. PMMoV poses a major threat to the global shortage of pepper plants and other Solanaceae crops due to the lack of an effective antiviral agent. In this study, we have developed a plant immune inducer (vanisulfane), as a "plant vaccine" that boosts plant immunity against PMMoV, and studied its resistance mechanism. The protective activity of vanisulfane against PMMoV was 59.4%. Vanisulfane can enhance the activity of defense enzymes and improve the content of chlorophyll, flavonoids, and total phenols for removing harmful free radicals from plants. Furthermore, vanisulfane was found to enhance defense genes. Label-free quantitative proteomics would tackle disease resistance pathways of vanisulfane. According to Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, differentially abundant proteins (DAPs) are mainly involved in starch and sucrose metabolism, photosynthesis, MAPK signaling pathway, and oxidative phosphorylation pathway. These results are crucial for the discovery of new pesticides, understanding the improvement of plant immunity and the antiviral activity of plant immune inducers.

A series of novel chromone derivatives containing dithioacetals were prepared, and their antiviral activity against tomato spotted wilt virus (TSWV) was studied. The results showed that compounds A1−A31 had good inhibitory activity against TSWV. The 3D-QSAR model was built to analyze the structure−activity relationship of the compounds. We further found that compounds A32 and A33 had excellent anti-TSWV activities based on the results of 3D-QSAR, which were better than the control agents ningnanmycin and ribavirin. To study the mode of action of these compounds on TSWV, the nucleocapsid protein of TSWV (TSWV N) was cloned, expressed, and purified in the study. The results of the microscale thermophoresis (MST) experiments indicate that compound A33 can better bind with TSWV N. The molecular docking experiment further indicated that the mode of action of the compound A33 is to inhibit the virus by blocking the combination of TSWV N and viral RNA. Therefore, this study has found that chromone compound A33 is a potential anti-TSWV agent that targets TSWV N.

The development of effective antibacterial agents equipped with novel action modes and unique skeletons starting from natural compounds serves as an important strategy in the modern pesticide industry. Disclosed here are a series of novel indole derivatives containing pyridinium moieties and their antibacterial activity evaluation against two prevalent phytopathogenic bacteria, Xanthomonas oryzae pv. oryzicola (Xoc) and X. oryzae pv. oryzae (Xoo). A three-dimensional (3D)-QSAR model was adopted to discover higher activity like title compounds based on the Xoc antibacterial activity of the tested compounds. Compound 43 was consequently designed, and it displayed higher antibacterial activity as expected with the half-maximal effective concentration EC50 values of 1.0 and 1.9 μg/mL for Xoo and Xoc, respectively, which were better than those of the commercial drug thiodiazole copper (TC) (72.9 and 87.5 μg/mL). Under greenhouse conditions, the results of a rice in vivo pot experiment indicated that the protective and curative activities of compound 43 against rice bacterial leaf streak (BLS) and rice bacterial blight (BLB) were 45.0 and 44.0% and 42.0 and 39.3%, respectively, which were better than those of the commercial agent thiodiazole copper (38.0 and 37.9%, 38.6 and 37.0%) as well. Scanning electron microscopy images, defense enzyme activity tests, and proteomic techniques were utilized in a preliminary mechanism study, suggesting that compound 43 shall modulate and interfere with the physiological processes and functions of pathogenic bacteria.

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The specific conation of our research is to invent a series of indole derivatives containing a 4,5-dihydro-1H-pyrazoline motif with effective antiviral activity. The anti-potato virus Y (PVY) activities of target compounds were systematically investigated. Most target compounds exhibited good PVY activities. Compound D40, which exhibited outstanding anti-PVY activities, was sieved using a three-dimensional quantitative structure–activity relationship. Based on the anti-PVY activity assessments, the curative and protective activities of D40 were found to be 64.9 and 60.8%, respectively, which were superior to those of the commercial drug Ningnanmycin (50.2 and 50.7%, respectively). In addition, defensive enzyme activities and proteomics results indicate that D40 can increase the three crucial defense-related enzyme activities and regulate the carbon fixation pathway in photosynthetic organisms to intensify the resistance of plants to PVY. Therefore, our study suggests that compound D40 might be used as a suitable crop protection pesticide.