Fig. 6. AtRPS5A and AtRPS5B are differentially expressed in seedlings. Four-day-old seedlings from pAtRPS5A::GUS (A-C) and pAtRPS5B::GUS (D-F) plants were stained for GUS activity during 10 minutes and 2 hours, respectively. The AtRPS5A promoter is strongly active in the division zone of the primary root tip (A) and the SAM and leaf primordia (C), and is weaker in the pericycle of the root (B). pAtRPS5B is active in the epidermal cells of the primary root tip (D), in a zone more distal from the tip than pAtRPS5A. Activity is almost absent in the root pericycle (E), but present in lateral root primordia (not shown). GUS activity is also found in the distal, differentiating cells of the shoot primordium, but absent from the SAM (F). AtRPS5B (H), but not AtRPS5A (G) is expressed in root hairs.