Spatial and temporal expression patterns of GUS reporter gene driven by P-miR164a in transgenic Arabidopsis plants. (A) Leafs from 4 week old plants of the different lines used for this study. A1: Control 35S::GUS transgenic Arabidopsis line. A2, A3 and A4: three independent P-miR164a::GUS transgenic Arabidopsis lines with showing low, intermediate or strong GUS activity (lines L35, L50 and L56 respectively). A5: Control EV::GUS transgenic Arabidopsis line where no GUS staining was detected. (B) GUS staining of plants, organs or sections of the control 35S::GUS transgenic Arabidopsis line (B1, B3 and B5) and P-miR164a::GUS L56 transgenic plants (B2, B4, B6 to B9). (B2) Staining leafs of one week-old plants. (B4) Mature and immature flowers. (B6) Detail of dehiscence zone of the siliques. (B7) Flower transverse section showing the reporter gene activity in the septum that divides both locus from each theca. (B8 and B9) Stem transverse sections with GUS staining found in developing xylem vessels. (C) Time course of P-miR164a transcription activity during the development of P-miR164a::GUS L56 transgenic plants. The plants were stained from stages 1.04 to stage 8. The most intense GUS staining was observed in stages 1.13 to 5.1. Bar = 0.5 cm.