DELLAs promote ARR1 activity.

(A) Expression in Arabidopsis roots of GFP under the control of the CK- and ARR1-responsive TCS element, after treatments with 0.5 μM trans-zeatin and 1 μM GA4. (B) Luciferase assays in N. benthamiana leaves agroinfiltrated with HA-ARR1, YFP-GAI, and myc-M5GAI, using the LUC gene under the control of the wild-type and mutant versions of the TCS element, and the constitutively expressed Renilla luciferase (REN) for normalization. The values represent the ratio between both luciferase activities and are the average of three biological replicates. Error bars are the standard deviation. One and two asterisks denote statistical significance (p<0.05 and p<0.005 respectively). The lower panel contains the western-blot analysis of the protein samples corresponding to equal mixtures from the three leaves used for the LUC assays with the wild-type TCS elements.