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Tobacco bacterial wilt has seriously affected tobacco production. Ethyl methanesulfonate (EMS) induced tobacco bacterial wilt resistant mutants are important for the control of tobacco bacterial wilt. High-throughput sequencing technology was used to study the rhizosphere bacterial community assemblages of bacterial wilt resistant mutant tobacco rhizosphere soil (namely KS), bacterial wilt susceptible tobacco rhizosphere soil (namely GS) and bulk soil (namely BS) in Xuancheng, Huanxi, Yibin and Luzhou. Alpha analysis showed that the bacterial community diversity and richness of KS and GS in the four regions were not significantly different. However, analysis of intergroup variation in the top 15 bacterial communities in terms of abundance showed that the bacterial communities of KS and GS were significantly different from BS, respectively. In addition, pH, alkali-hydrolysable nitrogen (AN) and soil organic carbon (SOC) were positively correlated with the bacterial community of KS and negatively correlated with GS in the other three regions except Huanxi. Network analysis showed that the three soils in the four regions did not show a consistent pattern of network complexity. PICRUSt functional prediction analysis showed that the COG functions were similar in all samples. All colonies were involved in RNA processing and modification, chromatin structure and dynamics, etc. In conclusion, our experiments showed that rhizosphere bacterial communities of tobacco in different regions have different compositional patterns, which are strongly related to soil factors. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cembranoids were systematically separated by an activity-oriented approach. • Enriched the antifungal, insecticidal, and cytotoxic activities of diverse cembranoids. • Cembranoid activities might be influenced by hydroxyl groups and unsaturation. • Cembranoid kill insects by restraining acetylcholinesterase activity. • Cembranoids are promising for developing bio-pesticides and bio-medicines. Cembranoids are a class of glandular trichome exudates with a variety of structural variations and biological activities, and are found in high quantities in tobacco (Nicotiana tabacum L.). However, few studies have conducted preparative separation and examined the activities of cembranoids other than (1 S ,2 E ,4 S ,6 R ,7 E ,11 E)-2,7,11-cembratriene-4,6-diol (α -CBT-diol, 1) and (1 S ,2 E ,4 R ,6 R ,7 E ,11 E)-2,7,11-cembratriene-4,6-diol (β -CBT-diol, 2); thus, the structure-activity relationship (SAR) of cembranoids remains unclear. Here, to deduce the SAR of cembranoids, raw cembranoid extract was systematically separated through an activity-oriented approach with preparative reversed-phase liquid chromatography. Each fraction was identified, and their antifungal, insecticidal, and cytotoxic bioactivities were evaluated. Composition analysis and activity detection of primary fractions (Fr.1–Fr.10) revealed that cembranoid activity might be influenced by the number of hydroxyl groups and degree of unsaturation (macrocycle and double bonds). Sub-fraction analysis showed that the antifungal activity of cembranoids was related to the number of hydroxyl groups and double bonds, and that their cytotoxic activity was affected by the type and position of substituents. Furthermore, all four factors could influence insecticidal activity. By conducting in-depth studies of single cembranoids, their SARs were summarized. The existence of Δ11,12/Δ7,8 and hydroxylation at C-6/C-4 contributed to the antifungal activity of cembranoids. Variation in the type and position of substituents also significantly affected antifungal activity, of which Δ11,12 was the most influential factor. Additionally, the change in substituent configuration at C-4 and C-12 had no significant effect on antifungal activity. The insecticidal activity of cembranoids benefited from the existence of 4-hydroxyl, which greatly enhanced their binding affinity; however, functional groups substituted at other positions decreased insecticidal activity. Cytotoxic activity was positively correlated with α -configuration at C-4 and hydroxylation at C-6 but inversely correlated with 4-methoxy substitution. Among them, 6-hydroxyl formed the core; the α -/ β -configuration at C-12 and 4-/12-substitution of cembranoids did not affect their insecticidal activity. Insecticidal activity might play a key role by restraining acetylcholinesterase activity through hydrophobic interactions between the cembranoid carbon skeleton and residues located at the acetylcholinesterase binding pocket. These findings may provide a foundation for the development of novel cembranoid-based pesticides and medicines. [ABSTRACT FROM AUTHOR]