Arabidopsis
Inoculation of Arabidopsis roots with each of the three rhizobacteria
resulted in significant changes in the shoot metabolome. From the 725
detected metabolites, 465 (64%) were significantly different between at
least two treatments. In the PCA, the first three principal components
explained 89% of the total variance (Figure 2a1 ). The first
principal component (PC1), representing 56% of the total variance, was
associated with metabolites that were highly induced (Figure
2a2 clusters 5 ; 291 metabolites and 6 ; 10
metabolites) or reduced in the ineffective partnership betweenPbg and Arabidopsis (clusters 3 ; 82 metabolites and4 ; 33 metabolites). Pbg -induced metabolites in cluster5 primarily encompassed flavonoids including anthocyanins
(cyanidin rutinoside, delphinidin rutinoside), tryptophan and its
derivatives such as IAA, defense or stress-associated metabolites such
as salicylic acid, dihydroxybenzoic acid glucosides, copoline and
camalexin. The second principal component (PC2) explained 21% of the
total variance and corresponded to metabolites that were increased
(Figures 2a1 and a2 clusters 2 ; 18 metabolites and6 ; 9 metabolites) or decreased (cluster 7 ; 10
metabolites) in the effective partnership of Arabidopsis with PfSS101 and MB. Among the identified metabolites, the long-chain aliphatic
glucosinolate glucohirsutin
(8-(methylsulfinyl)octyl
glucosinolate) was significantly increased in Arabidopsis shoot after
inoculation with Pf SS101 or MB. From the same group of
glucosinolates, 8-(methylthio) octyl glucosinolate was significantly
increased after inoculation with Pf SS101 (Supplementary
Material, Table S4 ). The third principal component (PC3)
explained 12% of the total variation and was represented by metabolites
that accumulated only after inoculation with either Pf SS101 or
MB (Figures 2a1 and 2a2 cluster 1 ; 8
metabolites and cluster 9 ; 7 metabolites, respectively). A
fatty acyl glycoside demonstrated Pf SS101-specific accumulation
while fumaric acid displayed MB-specific increases.