Figure 1: Generation of a lateral root transcriptomic data set.

(a) Overview of lateral root primordium stages, as described in ref. 10. Image adapted from ref. 14. (b) Gravitropic stimulation was used to induce the synchronized initiation of lateral root primordia at the site of root bending in a population of 3-day-old seedlings. Lateral root primordium stages (from I to VIII according to previous descriptions from ref. 10) were determined every 3 h from 6 to 54 h post gravity induction and are represented here as a percentage of the total number of observed lateral root primordia at each time point¹⁴. (c) Root bends were microdissected for each of those 18 time points and used for RNA extraction and subsequent microarray analysis (N=450 per time point, 4 independent biological replicates). All seedlings were grown in constant light conditions, without previous entrainment. Image is adapted from ref. 14. (d) Principal component analysis of the lateral root data set revealed an oscillating component in the third principal component (PC3). (e) When differentially expressed genes were clustered, 17 clusters showed an oscillatory pattern. The estimate of the period length (h) and the number of genes in each cluster (N=x) is indicated above each cluster. Clusters with blue lines comprise core circadian clock genes. Expression intensities are on a log2 scale. The mean of the clusters is given by the solid line and the dotted lines show the mean±2s.d.