Figure 4.

Truncation assay of Pptca2 to screen the critical regulatory region for CO₂ and light responses. A, A series of upstream truncation was carried out on Pptca2 (−1312 to +47) and each truncated sequence was fused with uidA (left half) and the GUS reporter assay was done with each transformant (right half). Cells were grown in 5% CO₂ or air in the absence or presence of light. Vertical bar indicates the dataset for each construct. Two independent clones of transformants carrying each manipulated promoter-reporter construct were selected for a set of reporter assays. Value is mean ± sd of three replicates. Statistical significance was determined by t test (**, P < 0.01; ***, P < 0.001). B, The primary structure of the newly found core-regulatory region of Pptca2, which contains one CCRE1 and two CCRE2 sequences.