Figure 3.

Auxin production by Frankia. A, Auxin content measured by LC-MS in the supernatant of in vitro Frankia CcI3 cultures. Bacteria were grown in BAP medium with (+N) or without (−N) nitrogen sources. Data are means ± sd. Significance was tested by an ANOVA test. * P < 0.01 compared with noninoculated. B to C, Putative IAA (B) and PAA (C) biosynthetic pathways identified in Frankia CcI3 using genome data mining. Frankia CcI3 orthologs were identified for the three key enzymes in the indole-3-pyruvate and the phenyl pyruvate pathways (see Supplemental Table S1). Expression of the corresponding genes in Frankia CcI3 bacteria grown in BAP medium with or without a nitrogen source was analyzed by qRT-PCR. Fold changes values represent the mean ratios of expression changes in BAP−N relative to BAP+N medium in two independent biological replicates.