Fig. 3: MtCEP7 expression pattern in rhizobium-inoculated roots.

a–h Expression pattern of a pCEP7:GUS transcriptional fusion. The GUS activity was analyzed in roots uninoculated (a) or inoculated with rhizobia 4 h post inoculation (hpi; b, c), 24 hpi (d, e), 4 days post rhizobial inoculation (dpi; f, g), or in a nodule primordium (5 dpi; h). c is a detail of b, and g is a detail of f, as indicated by white squares. All images show longitudinal roots, except e that is a transversal section. All images show the GUS staining as a blue signal in bright field microscopy. The arrowhead in g indicates an infection thread. At least eight independent roots were analyzed for each condition from five independent experiments. Scale bars = 200 µm. i Expression analysis of GUS transcripts in pCEP7:GUS transgenic roots, assessed by qRT-PCR. Expression levels were normalized relative to uninoculated roots (0 hpi). To highlight fold changes, the dotted line corresponds to a ratio of 1. Center lines show the medians; box limits indicate the 25th and 75th percentiles as determined by the R software; whiskers extend 1.5 times the interquartile range from the 25th and 75th percentiles, outliers are represented by dots; crosses represent sample means; and data points from three biological replicates are plotted as open circles (n = 9). Mann–Whitney test was used to assess significant differences between each time point and the non-treated control, as indicated by asterisks (***α < 0.001). j, k Expression pattern of the pCEP7:GUS transcriptional fusion in WT (j) versus nin mutant roots 4 dpi (k). In a–h, j, k, a minimum of eight independent roots per experiment were analyzed for each time point, and five independent experiments were performed. Images show the GUS staining as a blue signal in bright field microscopy. Scale bars = 200 µm.