PMC

NOD, nonenzymatic oxidative decarboxylation; ALS, α-acetolactate synthase, encoded by budB; ALDC, α-acetolactate decarboxylase, encoded by budA; DR-I, diacetyl reductase-I (glycerol dehydrogenase), encoded by gdh; DR-II, diacetyl reductase-II (meso-2,3-butanediol dehydrogenase), encoded by budC; DR-III, an undiscovered diacetyl reductase. Crosses represent the enzyme inactivation performed in this study.

HPLC chromatograms of the diacetyl. (A) standard (0.5 mg/L), (B) standard (5 mg/L), (C) general distilled spirits, (D) fruit wine, (E) microbrewery beer (diacetyl 3.655 mg/L), and (F) microbrewery beer (diacetyl 0.024 mg/L). Peak 1, diacetyl; Peak 2, 2,3-hexanedione (IS)

a A simplified wiring diagram for diacetyl chemotaxis. b Diacetyl caused inward current in VD5 and depolarization of VD5. Compared with Pre-diacetyl, p = 0.024 charge transfer, and 0.000 V_m. c Diacetyl caused outward current in AVA and hyperpolarization of AVA in wild-type (wt) but not AVA-targeted unc-49 RNAi strain. Compared with wt, p = 0.000 charge transfer, and 0.003 hyperpolarization. d AVA-targeted unc-49 RNAi reduced diacetyl chemotaxis response. Left: diagram showing the chemotaxis assay. At the beginning of each assay, a drop of diacetyl and NaN₃ mixture and a drop of diacetyl solvent and NaN₃ mixture were spotted on opposite sides of a nematode culture plate (6-cm diameter), and 10–15 worms were placed in the middle of the plate. Chemotaxis index was calculated as shown. Right: diacetyl concentration and chemotaxis index curves of wt and AVA-targeted unc-49 RNAi. Compared with wt, p = 0.043, 0.000, 0.023, and 0.839 at the four increasing glycerol concentrations, respectively. In b and c, the horizontal gray lines indicate the times of diacetyl application. Diacetyl (1:1000 dilution) was applied to the vicinity of the nose through a puffing pipette. Statistically significant differences from pre-diacetyl (b), wt (c), and wt at identical diacetyl concentrations (d) are indicated by asterisks indicate statistically significant difference (*p < 0.05, **p < 0.01, ***p < 0.001) compared with pre-diacetyl or wt based on either paired two-sided t-test (b) or unpaired two-sided t-test (c, d). The numbers inside brackets indicate sample size (n). n = numbers of independently recorded cells in b and c, but numbers of individual worms in d. Data are presented as mean values ± SEM. Source data are provided as a Source data file.

The green nodes are the proteins acetylated in group treated with Diacetyl but lack acetylation on treated groups. The red nodes are the proteins presents only in group treated with Diacetyl; the blue nodes are the proteins presents only in control group and the purple nodes are proteins present in both groups.