Figure 3.

Phytochrome A phosphorylates Aux/IAA proteins in vitro. Recombinant oat phyA (AsPhyA) in the Pr form or Pfr form was used in kinase assays with recombinant IAA proteins as described in “Materials and Methods.” To detect any autophosphorylation of IAA proteins, assays were also performed without AsPhyA. Shown are autoradiographs of the kinase reactions after SDS-PAGE and protein transfer to membranes (top), and Coomassie Blue staining of the transferred proteins (bottom). Amounts of phyA autophosphorylation and of Aux/IAA phosphorylation by phyA are expressed relative to the reactions containing the Pr form of phyA and are given below the phyA protein bands and below the top panels, respectively.