Spodoptera frugiperda is a highly destructive migratory pest that threatens various crops globally. Autographa californica multiple nucleopolyhedrovirus (AcMNPV) is an effective biocontrol agent against lepidopteran pests. Here, we explored the molecular mechanisms underlying the immune response to AcMNPV infection in S. frugiperda. RNA-seq and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analyses identified the Toll, IMD, and apoptosis pathways as primary immune responses. Investigation into AcMNPV-induced apoptosis in the S. frugiperda cell line (Sf9) revealed that the Toll pathway activated the JNK via the TRAF6 (TNF receptor-associated factor 6) adapter. In addition, AcMNPV-induced the differential expression of several host-encoded microRNAs (miRNAs), with significant negative regulatory effects, on S. frugiperda antiviral immune genes. RNAi and miRNA-mimic mediated silencing of these genes resulted in increased AcMNPV proliferation. Our findings reinforce the potential of AcMNPV as a potent biocontrol agent and further our understanding of developing biotechnology-based targeted pest control agents.

Furanocoumarins, the secondary metabolites of plants, are considered to be natural insecticides and fungicides because they prevent the invasion of plant pathogenic microorganisms and the predation of herbivorous insects. In this study, novel 2-arylfuranocoumarin derivatives were designed to synthesize by condensation, esterification, bromination, and Wittig reaction. The results showed an excellent photosensitive activity of 2-thiophenylfuranocoumarin (I34). Cell Counting Kit-8 detected that I34 could inhibit the proliferation of Spodoptera frugiperda (Sf9) cells in a time- and concentration-dependent manner under ultraviolet A (UV-A) light for 3 min. The inverted microscope revealed that cells treated with I34 swelled, the membrane was ruptured, and apoptotic bodies appeared. The flow cytometry detected that I34 could induce apoptosis of Sf9 cells, increase the level of intracellular reactive oxygen species (ROS), decrease the mitochondrial membrane potential, and block cell cycle arrest in the G2/M phase. Transmission electron microscopy detected cell mitochondrial cristae damage, matrix degradation, and mitochondrial vacuolation. Further enzyme activity detection revealed that the enzyme activities of apoptosis-related proteins caspase-3 and caspase-9 increased significantly (p < 0.05). Finally, Western blotting analysis detected that the phosphorylation level of Akt and Bad and the expression of the apoptosis inhibitor protein Bcl-XL were inhibited, cleaved-PARP and P53 were increased, and cytochrome C was released from the mitochondria into the cytoplasm. Moreover, under UV-A irradiation, I34 promoted the increase in ROS in Sf9 cells, activated the mitochondrial apoptotic signal transduction pathway, and finally, inhibited cell proliferation. Thus, novel furanocoumarins exhibit a potential application prospect as a biochemical pesticide.

Chinese olive (Canarium album Raeusch.) is a traditional Chinese medicinal plant, mainly cultivated in Guangdong and Fujian provinces in China (Lai et al. 2022). In October 2023, Chinese olive fruit spots were observed in all the Chinese olive orchards surveyed in Chaozhou city (23.75°N, 116.67°E) of Guangdong, with an incidence up to 15%. Early disease symptoms on fruits appeared as circular or irregular, dark brown to black spots with yellowish lesions, and later the spots slowly coalesced to form large necrotic areas, which seriously affected the fruit marketability. To isolate the causal agent, small pieces (~0.3 mm2) of fruit tissue were excised from the lesion margins, and surface-disinfested with 75% (v/v) ethanol for 1 min, followed by 1% NaClO for 3 min, and rinsed three times with sterile water. The pieces were then placed on potato-dextrose-agar (PDA) and incubated at 27°C. Ultimately, four fungal isolates were obtained with similar morphology phenotypes, colonies initially appeared white with irregular margins and after 4-6 days turned dark gray gradually with dense aerial myceliu. Microscopy revealed conidia were single-celled, hyaline, aseptate, fusiform to subclavate, and measured 18.1-22.5 μm × 6.4-9.3 μm (19.8 × 7.4 m on average, n = 30), which were consistent with those descriptions of Botryosphaeria dothidea (Vasić et al. 2013; Zhang et al. 2023). To further identity the isolates, partial sequences of ribosomal transcribed spacer (ITS), translation elongation factor 1-α (TEF1-α), and β-tubulin (TUB2) genes were amplified using primers ITS1/ITS5, TEF-F/R, TUB2-F/R, respectively (Xu et al., 2023; Hong et al. 2006). The sequences of four isolates were identical, and those of representative strain GDCZ-1 were deposited in GenBank (ITS, OR584295; TEF1-α, OR685157; TUB2, OR685158). Using Neighbor-Joining algorithm, phylogenetic tree based on concatenated sequences of ITS, TEF1-α, and TUB2 showed that GDCZ-1 clustered with B. dothidea. To fulfill Koch's postulates, pathogenicity tests were performed on healthy Chinese olive fruits using the needle-prick inoculation method. The fruits were wounded with a sterile needle at the equatorial area (depth of 3-4 mm), and inoculated with 10 µL of spore suspension (106 /mL). The control fruits were inoculated with sterile water. Inoculated fruits were placed in sterile plastic containers to maintain high relative humidity (almost 100%) and incubated at 27°C. After 4 days, the inoculated fruits showed similar symptoms with those observed in the field infected fruits, while the control remained asymptomatic. Pathogen re-isolated from the inoculated fruits showed identical morphological characteristics to the original isolate GDCZ-1. As far as we know, fruit rot caused by Alternaria alternata has been recently reported on C. album in China (Shao et al. 2024). To our knowledge, this is the first report of B. dothidea causing fruit rot disease on C. album in Guangdong. Our report will provide crucial information for studying the epidemiology and management of this disease.

Xinjiang is an autonomous province in northwest China