Figure 9.

Summary of the evolutionary history of root hair gene families. The tree indicates the distribution and putative origin of root hair gene expression in the 10,311 gene families (blue numbers) possessing one or more root hair-expressed genes identified in this study. Positive numbers refer to putative lineage-specific gain of families containing root hair-expressed genes, and negative numbers refer to putative lineage-specific loss of families containing root hair-expressed genes. The numbers in red specifically indicate the evolutionary history of the 404 key Arabidopsis root hair gene families (397 AtRHM + seven patterning gene families). Genes related to 6,179 of these families also are present in the root hair-less plant P. patens, indicated at the base of the tree (in brackets). For discussion, see text.