(a) Levels of induced resistance against H. arabidopsidis WACO9 in Arabidopsis (Col-0) after root treatment with L-Asp (150μM), R-BABA (150μM), or S-BABA (150μM). Insets show different classes of pathogen colonization; asterisk indicates a statistically significant difference in class distribution relative to water-treated plants (Fisher’s exact test, p<0.01, n=50-100). (b) Mass spectrometry analysis of BABA from immunoprecipitated IBI1:YFP of ibi1-1 35S:IBI1:YFP-1 or un-transformed Col-0 (negative control), using MALDI-qTOF ([M+H]; m/z=104,025). Left panels show standards (R-BABA and S-BABA; 1 μM). Immunoprecipitation (IP) was performed with protein extracts from leaves after two successive root treatments with water (control), R-BABA (1.2 mM), or S-BABA (1.2 mM). MALDI-qTOF analysis of IP extracts from ibi1-1 35S:IBI1:YFP-1 plants after R- or S-BABA applications was repeated twice from material of independent experiments, yielding similar results.