First report of leaf blight caused by Nigrospora hainanensis on Euonymus japonicus in China.

Euonymus japonicus Thunb., belonging to the family Celastreace and native to East Asia, is a widely cultivated evergreen ornamental woody plant with important ecological and economic values. In May 2023, serious leaf blight of E. japonicus occurred in the campus green space at Guiyang University, Guizhou Province, China (26°55'85"N, 106°78'04"E). Early symptom appeared as small, circular light brown spots on the edges or tips of the leaves. Then, the spot developed visible necrosis, initially light brown to dark brown halos with clear margins. Subsequently, severely infected leaves appear totally wilt, and significantly decrease their ornamental values. In a 0.07-ha field, the disease incidence reached to 40-55%. To identify the pathogen, ten typical symptomatic E. japonicus leaves were collected. They were initially immersed in 75% ethanol for 3 min, and by sodium hypochlorite (4% NaClO) solution for 45 s, and ultimately rinsed with sterile distilled water (dH2O) five times for not less than 1 min each time, then, placed the leaves on potato dextrose agar (PDA) medium and cultured for 5 days at 25°C in constant temperature incubator. Cultures were purified to yield eight isolates. Early colonies are white and regularly rounded, gradually turning dark brown to black with fluffy mycelium. Conidia were single celled, smooth, black, spherical or ellipsoidal. The conidia size of the representative strain, GY-2 and GY-3, was averagely 12.3-17.3 µm × 10.8-17 µm (n = 50). The conidiogenous cells were monoblastic, hyaline, globose or ampulliform. Morphology-based identification revealed the strain as Nigrospora spp. (Wang et al., 2017). For further confirmation, PCR of GY-2 and GY-3 DNA was performed with the primers ITS1/ITS4 (White et al., 1990), Bt2a-F/Bt2b-R (Glass and Don-aldson 1995), and TEF1-728F/TEF1-986R (Carbone and Kohn 1999). Sequences of the ITS region, TUB and TEF1 genes from the strain GY-2 and GY-3 were deposited in GenBank. (GY-2: OR999377, PP112221 and PP150467; GY-3: PP406871, PP421045 and PP421046, respectively). BLAST analysis showed GY-2 100%, 100%, and 98.36%; GY-3 99.43%, 98.21% and 100% (ITS region, TEF1, and TUB) identity to N. hainanensis sequences (accession numbers. NR_153480.1, KY019415.1, and KY019464.1; KX986094.1, OP611475.1, and KY019597.1). Additionally, tandem sequences of ITS, TUB and TEF1 constructed by MEGA 7.0 confimed the homology through the phylogenetic tree. Pathogenicity tests were conducted on healthy plants grown, each 5 mm diameter of active growing mycelium plug of isolate GY-2 was attached to 15 leaves from five healthy 2-year-old E. japonicu plants. The same number of leaves in the control group were treated with non-inoculated plugs only. All the plants were incubated at 25°C and 75% relative humidity with a 16-h/8-h photoperiod. After 10 days, no symptoms appeared on the leaves of the control group. In contrast, symptomatic blight appeared on all leaves inoculated with GY-2. Pathogenicity tests were performed five times. Pure strains were re-isolated from diseased leaves and, confirmed to be N. hainanensis based on the above methods. Recently, Nigrospora oryzae was reported as causal agent of leaf spots on Euonymus japonicus in China (Xu et al., 2023). To our knowledge, this study is the first report of N. hainanensis causing leaf blight on E. japonicu. Identification of the etiological agent may provide assistance for sustainable management in the future.

Large-scale interplant exchange of macromolecules between soybean and dodder under nutrient stresses.

Parasitic plants and their hosts communicate through haustorial connections. Nutrient deficiency is a common stress for plants, yet little is known about whether and how host plants and parasites communicate during adaptation to such nutrient stresses. In this study, we used transcriptomics and proteomics to analyze how soybean (Glycine max) and its parasitizing dodder (Cuscuta australis) respond to nitrate and phosphate deficiency (-N and -P). After -N and -P treatment, the soybean and dodder plants exhibited substantial changes of transcriptome and proteome, although soybean plants showed very few transcriptional responses to -P and dodder did not show any transcriptional changes to either -N or -P. Importantly, large-scale interplant transport of mRNAs and proteins was detected. Although the mobile mRNAs only comprised at most 0.2% of the transcriptomes, the foreign mobile proteins could reach 6.8% of the total proteins, suggesting that proteins may be the major forms of interplant communications. Furthermore, the interplant mobility of macromolecules was specifically affected by the nutrient regimes and the transport of these macromolecules was very likely independently regulated. This study provides new insight into the communication between host plants and parasites under stress conditions.

The overexpression of cytochrome P450 genes confers buprofezin resistance in the brown planthopper, Nilaparvata lugens (Stål).

BACKGROUND: Buprofezin, an insect growth regulator, has been widely used to control brown planthopper (BPH), Nilaparvata lugens, one of the most destructive pests of rice crops in Asia. The intensive use of this compound has resulted in very high levels of resistance to buprofezin in the field, however, the underpinning mechanisms of resistance have not been fully resolved. RESULTS: Insecticide bioassays using the P450 inhibitor piperonyl butoxide significantly synergized the toxicity of buprofezin in two resistant strains of BPH (BPR and YC2017) compared to a susceptible strain (Sus), suggesting P450s play a role in resistance to this compound. Whole transcriptome profiling identified 1110 genes that were upregulated in the BPR strain compared to the Sus strain, including 13 cytochrome P450 genes, eight esterases and one glutathione S-transferase. Subsequently, qPCR validation revealed that four of the P450 genes, CYP6ER1vA, CYP6CW1, CYP4C77, and CYP439A1 were significantly overexpressed in both the BRP and YC2017 strains compared with the Sus strain. Further functional analyses showed that only suppression of CYP6ER1vA, CYP6CW1, and CYP439A1 gene expression by RNA interference significantly increased the toxicity of buprofezin against BPH. However, only transgenic Drosophila melanogaster expressing CYP6ER1vA and CYP439A1 exhibited significant resistance to buprofezin. Finally, the BPR strain was found to exhibit modest but significant levels of resistance to acetamiprid, dinotefuran and pymetrozine. CONCLUSIONS: Our findings provide strong evidence that the overexpression of CYP6ER1vA and CYP439A1 contribute to buprofezin resistance in BPH, and that resistance to this compound is associated with low-level resistance to acetamiprid, dinotefuran and pymetrozine. These results advance understanding of the molecular basis of BPH resistance to buprofezin and will inform the development of management strategies for the control of this highly damaging pest. © 2022 Society of Chemical Industry.

Inheritance and fitness cost of buprofezin resistance in a near-isogenic, field-derived strain and insecticide resistance monitoring of Laodelphax striatellus in China.

BACKGROUND: Laodelphax striatellus is one of the most destructive pests of rice and other cereal crops. Chemical control is still the most efficient way to control this pest, but insecticide resistance always threatens this approach. RESULTS: Monitoring data (2003-2020) showed that Chinese field populations of L. striatellus developed high-level buprofezin resistance within the first four years. This high-level resistance to buprofezin was stable for about ten years and persisted even when buprofezin selection pressure was absent. An established near-isogenic strain (YN-NIS) with 90.8-fold resistance to buprofezin had resistance inheritance of autosomal and incomplete dominance, and the resistance was controlled by multiple genes with no obvious fitness costs (relative fitness of 0.8707). Furthermore, the susceptibility of 29 field populations to another seven insecticides (2014-2020) showed that: (i) low-level resistance to pymetrozine, dinotefuran, sulfoxaflor and thiamethoxam was first detected in 2014 (eight years after introduction), 2016 (three years after), 2017 (four years after) and 2019 (19 years after), respectively, (ii) moderate resistance levels to chlorpyrifos were found for all populations across multiple years, and (iii) no resistance was detected for nitenpyram and triflumezopyrim. CONCLUSION: The fast buprofezin resistance development in L. striatellus would be caused by incomplete dominant resistance with almost no fitness cost in the resistant strain. Nitenpyram and triflumezopyrim showed no resistance and can be used as the main insecticide for the control of L. striatellus. These findings provide key fundamental information for controlling L. striatellus.

Baseline determination, susceptibility monitoring and risk assessment to triflumezopyrim in Nilaparvata lugens (Stål).

Triflumezopyrim, a novel mesoionic chemical insecticide, is promoted as a powerful tool for control of susceptible and resistant hopper species in rice throughout Asia. For a newly commercialized insecticide it is important to establish susceptibility baseline, conduct susceptibility monitoring, and assess the risk of resistance via artificial selection to provide foundational information on designing resistance management strategy. The susceptibility baseline of triflumezopyrim was established for three rice planthopper species, Nilarpavata lugens (Stål), Sogatella furcifera (Horváth) and Laodelphax striatellus (Fallén). The LD50 of triflumezopyrim was 0.026, 0.032 and 0.094 ng/individual for the adults of the susceptible strains of S. furcifera, L. striatellus and N. lugens, respectively, determined by a topical application method. Using a rice stem (seedling) dipping method, the LC50 was determined as 0.042, 0.024 and 0.150 mg/L for the nymphs (3rd instar) of the three hopper species, respectively. In the meanwhile, the LC50 of Pyraxalt™ (triflumezopyrim 10% SC) was 0.064 mg/L for the N. lugens susceptible strain. Furthermore, the susceptibility of triflumezopyrim and other five neonicotinoid insecticides were monitored for N. lugens field populations collected from major rice production areas in China in 2015-2019. All monitored populations were susceptible to triflumezopyrim (0.5 to 3.9-fold resistance ratio), and showed no cross-resistance to the other five neonicotinoids. These results suggested that triflumezopyrim is a good option to control resistant N. lugens. In addition, a field-collected population of N. lugens was artificially selected with triflumezopyrim for 20 generations and resulted in 3.5-fold increase in LC50 from F0 and 6.0-fold increase from that of the susceptible strain. The realized heritability (h2) of resistance was estimated as 0.0451 by using threshold trait analysis. With this h2 value, the projected triflumezopyrim resistance development (a 10-fold increase in LC50) would be expected after 30.3 or 24.0 generations if 80% or 90% of the population was killed at each generation.

Interleukin-32 promotes lipid accumulation through inhibition of cholesterol efflux.

Interleukin-32 (IL-32) is a pro-inflammatory cytokine and its effects in various inflammatory diseases have been investigated. However, the role of IL-32 on atherosclerosis, an inflammatory disease, remains unknown. The present study examined the use of IL-32α, the most abundant transcript of IL-32, in the treatment of oxidized low-density lipoprotein (ox-LDL)-stimulated THP-1 macrophages for 24 h, which simulates a foam cell formation model. The effect of IL-32α (20, 50 and 100 ng/ml) on lipid deposition in the macrophages was analyzed using Oil Red O staining, while the cholesterol efflux on apolipoprotein A-I was also measured. The mRNA and protein expression levels of peroxisome proliferator-activated receptor γ (PPARγ), liver X receptor α (LXRα), ATP-binding cassette transporter A1 (ABCA1) and ABCG1 were quantified by reverse transcription-quantitative polymerase chain reaction and western blot analysis, respectively. The results indicated that IL-32α exposure enhanced the lipid deposition and attenuated the cholesterol efflux from ox-LDL-stimulated THP-1 macrophages in a dose-dependent manner. Furthermore, the expression levels of ABCA1, LXRα and PPARγ were dose-dependently decreased by IL-32α at the mRNA and protein levels. Addition of the PPARγ agonist 15d-PGJ2 or overexpression of PPARγ in THP-1 macrophages abrogated the IL-32α-mediated inhibition of cholesterol efflux and reversed the IL-32α-mediated downregulation of ABCA1 and LXRα. In conclusion, IL-32α enhances lipid accumulation and inhibits cholesterol efflux from ox-LDL-exposed THP-1 macrophages by regulating the PPARγ-LXRα-ABCA1 pathway.