Xanthomonas oryzae pv. oryzicola (Xoo) is a plant pathogen responsible for rice bacterial blight disease that remains challenging for prevention and cure. To discover innovative and extremely potent antibacterial agents, vanillin moiety was introduced to develop a series of novel mesoionic derivatives. Compound 15 demonstrated excellent in vitro antibacterial activity against Xoo, with a 50% effective concentration value (EC50) of 27.5 μg/mL, which was superior to that of the positive control agent thiodiazole copper (97.1 μg/mL) and comparable to that of compound “A11” (17.4 μg/mL). The greenhouse pot experiment also revealed that compound 15 had 38.5% curative and 36.8% protective efficacy against rice bacterial leaf blight in vivo at 100 μg/mL, which was higher than those of thiodiazole copper (31.2 and 32.6%, respectively) and compound “A11” (29.6 and 33.2%, respectively). Compound 15 enhanced the activities of related defense enzymes, increased chlorophyll content, and promoted the resistance of rice to bacterial infection by modulating the photosynthetic pathway. This study provides a basis for the subsequent structural modification and mechanism research of mesoionic derivatives.

Heterodera glycines is one of the most destructive pathogens of soybean. Soybean seeds coated with Bacillus simplex Sneb545 have shown resistance to H. glycines as a result of induced systemic resistance (ISR) in the plants. In this study, we aimed to identify the resistance-inducing determinants from this B. simplex strain. Combining the ISR bioassay, six ISR-active compounds were isolated from a culture of B. simplex Sneb545 using organic solvent gradient extraction, silica gel column chromatography, Sephadex LH-20 column chromatography, and semi-preparative high-performance liquid chromatography (HPLC), and all systems were based on activity tracking. The compounds were determined as cyclic(Pro-Tyr), cyclic(Val-Pro), cyclic(Leu-Pro), uracil, phenylalanine, and tryptophan using 1 H nMR and 13 C NMR. In plants from seeds coated with Bacillus simplex Sneb545, these six ISRactive compounds delayed the development of H. glycines in soybean roots. Moreover, cyclic(Pro-Tyr), cyclic(Val-Pro), and tryptophan reduced the number of nematodes in soybean roots. The expression levels of defense-related genes with cyclic(Val-Pro), tryptophan and uracil treatment soybean analysed using Quantitative real-time PCR (qRT-PCR). The results indicate cyclic(Val-Pro), tryptophan and uracil induced the expression of defense-related genes involved in the SA-and JA-pathways to against H. glycines. Our research results provide new agents for the control of H. glycines. Soybean is an important economic crop, which is widely used in oil and food production. The United States of America, Brazil, and Argentina are the top three producers of soybean, producing approximately 123.7, 117.0, and 55.0 million metric tons annually, respectively, China is ranked fourth globally, with a production of 15.9 million metric tons per year (https ://soyst ats.com/inter natio nal-world-soybe an-produ ction , 2019). Heterodera glycines (soybean cyst nematode, SCN) is one of the most destructive pathogens of soybean 1. This nematode is a considerable threat to soybean production and is responsible for annual losses of up to USD 1.5 billion globally 2. Chemical nematicides are widely used to control parasitic nematode disease in soybean 3. However, their application not only causes widespread environmental pollution but also threatens human health. In addition, drug tolerance of nematodes has been enhanced by the long-term use of chemical nematicides 4,5. It is necessary, therefore, to seek safe, effective, and environmentally friendly products to defend soybean plants against SCN 6. The life cycle of SCN consists of four juvenile stages (J1-J4). The embryo in the egg develops into the first stage (J1) of juvenile and then molts in the egg to form the infested second-stage juveniles (J2). The J2 penetrates the root of the host plant, once J2 reach the vascular cylinder, they will establish a feeding site at the root, and then begins to develop into the third (J3) and fourth (J4) juvenile stages in the root system. Finally, matures to an adult female or male an...

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Plant virus diseases, also known as “plant cancers”, cause serious harm to the agriculture of the world and huge economic losses every year. Antiviral agents are one of the most effective ways to control plant virus diseases. Ningnanmycin is currently the most successful anti-plant virus agent, but its field control effect is not ideal due to its instability. In recent years, great progress has been made in the research and development of antiviral agents, the mainstream research direction is to obtain antiviral agents or lead compounds based on structural modification of natural products. However, no antiviral agent has been able to completely inhibit plant viruses. Therefore, the development of highly effective antiviral agents still faces enormous challenges. Therefore, we reviewed the recent research progress of anti-plant virus agents based on natural products in the past decade, and discussed their structure-activity relationship (SAR) and mechanism of action. It is hoped that this review can provide new inspiration for the discovery and mechanism of action of novel antiviral agents.

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