(A) Representative chromatograms from a targeted tandem MS-based analysis of Compound 6 in leaves of N. attenuata (bottom panel) and as comparison, a blumenol A-9-O-glucoside (roseoside) standard (top panel). The precursor-to-product ion transitions are indicated. (B) Time lapse accumulations of Compound 6 in roots of EV plants with (EV+, green line) or without (EV-, black line) AMF-inoculation. Data represent means ±SE (n ≥ 3). (C) Time lapse accumulations of Compound 6 in leaves of EV plants with (EV+, red line) or without (EV-, black line) AMF-inoculation and of irCCaMK plants with AMF-inoculation (irCCaMK+, orange line). Data represent means ±SE (n ≥ 5). (D) Comparison of the abundances of Compound 6 in leaves of plants inoculated with different inoculum concentrations, samples were harvested at 5 weeks-post-inoculation (wpi). Data are means +SE (n ≥ 4). Different letters indicate significant differences (p<0.05, one-way ANOVA followed by Fisher’s LSD). (E) Field experiment (Great Basin Desert, Utah, USA): leaf samples of EV (n = 20) and irCCaMK (n = 19) plants were sampled 8 weeks after planting and amounts of Compound 6 were analyzed. For statistical analysis, Student’s t test was applied. (F) Abundance of Compound 6 relative to the transcript abundance of the R. irregularis specific housekeeping gene, Ri-tub (GenBank: EXX64097.1), as well as to the plant derived marker genes RAM1, Vapyrin, STR1 and PT4.The transcript abundance was quantified by q-PCR, relative to NaIF-5a (NCBI Reference Sequence: XP_019246749.1). The correlation between Compound 6 and transcript abundance of marker genes was analyzed by linear regression (lm) models. (G) Distribution of Compound 6 in different plant tissues, as indicated, of plants with (+AMF, n = 3, red bars) or without (-AMF, n = 1, black bars) AMF-inoculation. Samples were harvested at six wpi.