Figure 8.

A Model for the Role of the miR390/tasiARF/ARF Module during Lateral Root Growth.

The diagram illustrates the spatial expression patterns of TAS3a, miR390, and ARF4 in a lateral root primordium. Hatched regions indicate the territories of overlapping gene expression. The cell layers of the primary root are indicated (x, xylem; p, pericycle; e, endodermis; cx, cortex; ep, epidermis). TAS3a accumulates in the vasculature, miR390 in the xylem, and the pericycle and the primordium in the base and flanks. The positive feedback of ARFs on miR390 supports a homeostatic model in which miR390 and ARF abundance are tightly regulated, whereas the mutual repression of miR390 and ARF4 helps to reinforce the miR390 expression pattern by removing it from the center of the primordium. Dashed arrows indicate indirect relationships.