Figure 6.

Effect of ABI3 on the Transcriptional Activation Mediated by the bZIP53/bZIP10 Heterodimers.

(A) GUS reporter activity under the control of the 2S2 or CRU3 promoter was measured in transiently transformed Arabidopsis protoplasts after cotransfection of the effector constructs indicated. bZIP10, bZIP53, and ABI3 are expressed under the control of Pro35S. For immunodetection, 3xHA-epitope-tagged derivatives were used (see Supplemental Figure 3 online). The importance of bZIP heterodimerization was demonstrated by including bZIP10pp, which is impaired in zipper-mediated dimerization (Weltmeier et al., 2006). Given are mean values and standard deviation of four independent transfections.

(B) Immunoblot analysis of transiently transformed protoplasts confirms that expression of HA-bZIP10 is comparable to HA-bZIP10pp-untransformed control protoplasts. HA epitope-tagged proteins were detected using an α-HA antiserum. The arrow indicates HA-bZIP10 and bZIP10pp proteins, and the asterisk shows degradation products.

(C) Transient expression using a GUS reporter gene under the control of the 2S2 promoter. Combinations of bZIP53 and bZIP10 at different ratios (indicated are ratios of input DNA) in the presence (black bars) or absence (white bars) of ABI3 were used as effectors. The x axis values are expressed as GUS activity relative to NAN as described by Ehlert et al. (2006). Average values and standard errors from four transfections are shown.