Fig. 7. The AtRPS5A and AtRPS5B genes are differentially expressed during embryogenesis. Siliques of pAtRPS5A::GUS (A-E) and pAtRPS5B::GUS (G-K) plants were stained for GUS activity for 2 and 8 hours, respectively. (A) In pAtRPS5A::GUS lines, GUS activity is already observed at the 2-cell stage in both embryo and endosperm. GUS activity remains strong through the octant (B) and globular stage (C), and decreases after the transition (D) and late torpedo stage (E). Activity is strongest in the peripheral cell layer (C-E). Expression of pAtRPS5B::GUS in embryos is weak until the globular stage (G,H), but increases during the late globular (I), heart (J) and late torpedo (K) stages. Note that expression is strongest in the inner cell layers (I-K), and is visible in the provascular tissue (K). (F) Schematic representation of the differential expression pattern of AtRPS5A (yellow) and AtRPS5B (blue). Places where both genes are expressed are marked with green. (i) 2-cell, (ii) octant, (iii) globular, (iv) transition, (v) heart and (vi) torpedo stage.