Fig. 7: LPWJL-emitted (2R,3R)-2,3-butanediol is responsible for the activation of the airway-gut-brain axis during animal growth.
a A biosynthetic pathway of 2,3-butanediol production from pyruvate. b GC-MS for quantitative analysis of different metabolites emitted by LPWJL, LPWJLΔALS, and LPWJLΔALS_ALS strains. n = 3 biologically independent experiments. Representative image of Btl and Bnl expression in trachea and enterocytes, respectively (c, left), relative tracheal coverage (c, right), representative merged image of oxidized red and unoxidized green Timer in enterocytes (d, left), ratio of oxidized red to unoxidized green Timer (d, right), representative image of AstA expression in EECs (e, left), quantitative analysis of AstA+ EEC number (e, right), quantitative analysis of circulating DILP2 level (f), and body length (g) were analyzed. n = 3 biologically independent experiments in (c–g). Relative values of GF control animals without inhalation of LPWJL volatiles were taken arbitrarily as 1 (c, f). In all cases, GF embryos were treated either without (+none) or with inhalation of volatiles from LPWJL (+LPWJL) bacteria, LPWJL ΔALS (+LPWJL ΔALS) bacteria, or LPWJLΔALS_ALS (+LPWJLΔALS_ALS) bacteria during entire larval stages. In the case of co-stimulation, GF embryos were treated with inhalation of volatiles from both LPWJL ΔALS bacteria and (2R,3R)-2,3-butanediol (0.3% v/v) (+LPWJL ΔALS+2,3-butanediol). Larvae at 144 h AEL were used. In each gut sample, an area (0.1 mm2) of a microscopic image from a similar gut region was randomly selected to count the number of AstA+ cells (e). The gut is arranged from anterior to posterior, moving from top to bottom in the photo (c–e). Data are mean ± s.e.m. P values (**p < 0.01, ***p < 0.001, ns not significant) are indicated; one-way ANOVA with Tukey’s post hoc test in (c–g). Nuclei were stained with DAPI in blue. Scale bar, 50 μm. Genotypes, sample sizes, and statistical analyses are shown in Supplementary Data 1. Source data are provided in the Source Data file.
