Figure 4.

XCT Protein Levels Undergo Complex Regulation.

Levels of XCT-YFP-HA fusion protein expressed under the control of the 35S (A) or native promoter (B) were determined with an anti-HA antibody and normalized to Ponceau staining. Plants were maintained in 12:12 LD cycles or constant light (LL). Data in the top panels are the mean ± se of three to four independent experiments; white and black bars below traces represent light and dark periods, respectively. Representative immunoblots are shown in the bottom panels. Rubisco expression was determined using a specific antibody and is shown in the bottom panels. Rubisco levels are impaired in xct-2 mutants (right panel, first lane) and rescued by expression of XCT-YFP-HA; however, overexpression of XCT does not cause an increase in Rubisco (left panel).