First report of Alternaria alternata causing leaf blight on Actaea dahurica in China.

In July 2019, leaf blight on Actaea dahurica, a plant with high value in Chinese traditional medicine, was discovered in a 2 ha planting area in Heilongjiang Province (129.6°E, 44.6°N), China. Disease incidence was 90% in the field. Symptoms consisted of irregular black spots with gray margins on both sides of the leaf, often at the leaf margin, mostly on the older leaves. To isolate the pathogen, ten diseased leaves were randomly collected, surface disinfested, and 5 x 5 mm segments were removed from the margin of the lesions. Leaf segments were placed onto potato dextrose agar (PDA) and incubated at 25 ℃ for 7 days. Ten pure cultures with the same morphological characteristics were obtained from three leaves showing typical symptoms. Cultures on PDA initially had a cottony mycelium, white-gray to gray. After two to three weeks of growth, mycelium color changed from gray to black. Conidiophores were clustered, dark at the base, tapering to the apex, born from simple sublates, unbranched, with 1 to 5 septa, and 70.4-530.3 × 5-7.5 µm in size. Conidia were 12.5-82.5 × 5.2-20.3 µm, usually in chains, had 2 to 8 transverse septa, 0 to 4 longitudinal or oblique septa, and a smooth brown surface. Simple, pale, vimineous or verrucous beaks developed from the apical cells with 0 to 4 septa. The morphological characteristics were consistent with Alternaria species (Simmons, 2007). To fulfill Koch's postulates, pathogenicity tests were carried out on three-month-old A. dahurica plants. A spore suspension was prepared from PDA cultures of isolates SM0101 and SM0102 and adjusted to 105 spores/mL using a hemocytometer. Each leaf was sprayed with 2 mL of the spore suspension, then incubated at 25 ℃ for 7 days. The same number of healthy A. dahurica plants were sprayed with sterile water as a control. After 7 days, small brown necrotic spots appeared on inoculated plants, but the control group showed no symptoms. A fungus with the same characteristics as that used for inoculation was re-isolated from the lesions. This experiment was replicated three times, and the results of each experiment were consistent. Genomic DNA was extracted from isolates SM0101 and SM0102 and used for PCR amplification of the rDNA internal transcribed spacer regions (ITS), RNA polymerase II gene (RPB2) and Alternaria allergen a 1 (Alt a 1) gene sequences using the primer pairs ITS1/ITS4 (White et al. 1990), RPB2-5F2/RPB2-7CR (Khodaei and Arzanlou, 2013) and Alt-for/Alt-rev (Hong et al. 2005), respectively. The ITS (OL703042, OL616086), RPB2 (OL703043, OL898416), and Alt a 1 sequences (OL616087, OL898415) were deposited in GenBank. The sequences obtained in this study had the highest match to corresponding sequences of Alternaria alternata CBS 916.96 (AF347031, KC584375, AY563301). For isolate SM0101 the matches were ITS (461/461 bp), RPB2 (897/985 bp), and Alt a 1 (488/488 bp). For isolate SM0202 the matches were ITS (457/457 bp), RPB2 (893/985 bp), and Alt a 1 (484/484 bp). A phylogenetic analysis was performed using MEGA7 software. The alignment included sequences from 16 ex-type Alternaria species and the two isolates causing leaf blight on A. dahurica. Branch supports were calculated with 1,000 bootstrap replicates, and phylogenetic inference was performed using the maximum likelihood estimation. The fungus isolated from A. dahurica clustered with A. alternata. This is the first report of A. alternata on A. dahurica in the world. This report will help to identify the disease symptoms in the field and provides a basis for research into the occurrence, distribution, and control of leaf blight on A. dahurica.

Iristectorigenin C suppresses LPS-induced macrophages activation by regulating mPGES-1 expression and p38/JNK pathway.

ETHNOPHARMACOLOGICAL RELEVANCE: Nonsteroidal anti-inflammatory drugs (NSAIDs) have been used clinically to treat inflammatory diseases clinically. However, the adverse effects of NSAIDs cannot be ignored. Therefore, it is critical for us to find alternative anti-inflammatory drugs that can reduce adverse reactions to herbal medicine, such as Iris tectorum Maxim., which has therapeutic effects and can treat inflammatory diseases and liver-related diseases. AIM OF THE STUDY: This study aimed to isolate active compounds from I. tectorum and investigate their anti-inflammatory effects and action mechanisms. MATERIALS AND METHODS: Fourteen compounds were isolated from I. tectorum using silica gel column chromatography, Sephadex LH-20, ODS and high performance liquid chromatography, and their structures were identified by examining physicochemical properties, ultraviolet spectroscopy, infrared spectroscopy, mass spectrometry, and nuclear magnetic resonance spectroscopy. Classical inflammatory cell models were established using lipopolysaccharide (LPS)-stimulated RAW264.7 cells and rat primary peritoneal macrophages to examine the effect of these compounds. To examine the action mechanisms, the nitric oxide (NO) levels were measured by Griess reagent and the levels of inflammatory cytokines in the supernatant were measured by ELISA; The expressions of major proteins in prostaglandin E2 (PGE2) synthesis and the nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways were examined by Western blotting, and the mRNA expression levels were measured by quantitative real-time polymerase chain reaction; and the nuclear translocation of p65 was examined by high content imaging. Molecular docking was used to predict the binding of active compound to target protein. RESULTS: Our findings revealed that Iristectorigenin C (IT24) significantly inhibited the levels of NO and PGE2 without affecting cyclooxygenase (COX)-1/COX-2 expression in LPS-induced RAW264.7 cells and rat peritoneal macrophages. Furthermore, IT24 was shown to decrease the expression of microsomal prostaglandin synthetase-1 (mPGES-1) in LPS-induced rat peritoneal macrophages. IT24 did not suppress the phosphorylation and nuclear translocation of proteins in the NF-κB pathway, but it inhibited the phosphorylation of p38/JNK in LPS-stimulated RAW264.7 cells. Additionally, molecular docking analysis indicated that IT24 may directly bind to the mPGES-1 protein. CONCLUSION: IT24 might inhibit mPGES-1 and the p38/JNK pathway to exert its anti-inflammatory effects and could be also developed as an inhibitor of mPGES-1 to prevent and treat mPGES-1-related diseases, such as inflammatory diseases, and holds promise for further research and drug development.