FIG. 3.

Hierarchical gene tree of expression from 13 experiments over the course of bacteroid development on peas (7, 15, and 21 days p.i. of 7 day-old plants and 28 days p.i. of seeds). The hierarchical tree was generated with the gene tree clustering algorithm in GeneSpring 7.2. using Pearson correlation and average linkage of the 386 genes that were ≥3-fold upregulated in nodule bacteria. Red indicates highly expressed genes, yellow intermediate, and blue low. Nine clusters can be distinguished and are indicated.