A pathogenesis-related protein 1 of Cucurbita moschata responds to powdery mildew infection

Pathogenesis related-1 proteins in plant defense: regulation and functional diversity

Climate change-related environmental stresses can negatively impact crop productivity and pose a threat to sustainable agriculture. Plants have a remarkable innate ability to detect a broad array of environmental cues, including stresses that trigger stress-induced regulatory networks and signaling pathways. Transcriptional activation of plant pathogenesis related-1 (PR-1) proteins was first identified as an integral component of systemic acquired resistance in response to stress. Consistent with their central role in immune defense, overexpression of PR-1s in diverse plant species is frequently used as a marker for salicylic acid (SA)-mediated defense responses. Recent advances demonstrated how virulence effectors, SA signaling cascades, and epigenetic modifications modulate PR-1 expression in response to environmental stresses. We and others showed that transcriptional regulatory networks involving PR-1s could be used to improve plant resilience to stress. Together, the results of these studies have re-energized the field and provided long-awaited insights into a possible function of PR-1s under extreme environmental stress.

Indole alkaloids isolated from the Nicotiana tabacum-derived Aspergillus fumigatus 0338 as potential inhibitors for tobacco powdery mildew and their mode of actions

To explore active natural products against tobacco powdery mildew caused by Golovinomyces cichoracearum, an extract from the fermentation of endophytic Aspergillus fumigatus 0338 was investigated. The mechanisms of action for active compounds were also studied in detail. As a result, 14 indole alkaloid derivatives were isolated, with seven being newly discovered (1-7) and the remaining seven previously described (8-14). Notably, compounds 1-3 are rare linearly fused 6/6/5 tricyclic prenylated indole alkaloids, with asperversiamide J being the only known natural product of this kind. The isopentenyl substitutions at the 5-position in compounds 4 and 5 are also rare, with only compounds 1-(5-prenyl-1H-indol-3-yl)-propan-2-one (8) and 1-(6-methoxy-5-prenyl-1H-indol3-yl)-propan-2-one currently available. In addition, compounds 6 and 7 are new framework indole alkaloid derivatives bearing a 6-methyl-1,7-dihydro-2H-azepin-2-one ring. The purified compounds were evaluated for their activity against G. cichoracearum, and the results revealed that compounds 7 and 9 demonstrated obvious anti-G. cichoracearum activities with an inhibition rate of 82.6% and 85.2%, respectively, at a concentration of 250 μg/mL, these rates were better than that of the positive control agent, carbendazim (78.6%). The protective and curative effects of compounds 7 and 9 were also better than that of positive control, at the same concentration. Moreover, the mechanistic study showed that treatment with compound 9 significantly increased the structural tightness of tobacco leaves and directly affect the conidiospores of G. cichoracearum, thereby enhancing resistance. Compounds 7 and 9 could also induce systemic acquired resistance (SAR), directly regulating the expression of defense enzymes, defense genes, and plant semaphorins, which may further contribute to increased plant resistance. Based on the activity experiments and molecular dockings, the indole core structure may be the foundation of these compounds' anti-G. cichoracearum activity. Among them, the indole derivative parent structures of compounds 6, 7, and 9 exhibit strong effects. Moreover, the methoxy substitution in compound 7 can enhance their activity. By isolating and structurally identifying the above indole alkaloids, new candidates for anti-powdery mildew chemical screening were discovered, which could enhance the utilization of N. tabacum-derived fungi in pesticide development.