Expression map of Arabidopsis thaliana PIN genes compiled from both promoter activity data and protein localization. Each PIN gene-expression domain is marked out by a colored line (see key in upper right corner. The organs depicted are (a) flower; (b) embryo (late globular stage); (c) stem; (d) rosette leaf; (e) mature part of the primary root; (f) lateral root primordium (stage 5); (g) root tip. The figure is based on the data from [11, 12, 14, 22, 23, 65, 66]. Note that PIN5 expression is not depicted, as it is expressed weakly throughout the aerial part of the plant with maxima in the hypocotyl, the guard cells of stomata, and cauline leaves [13, 65].