Figure 1.

Schematic drawings of the chimeric constructs and Ars expression of their corresponding transgenic lines. A, The 3′-nested deletions of a Cah1 upstream region were fused to the Ars reporter gene (Ars) driven by the β₂-tubulin minimal promoter (Pr). Asterisks represent positions of consensus sequences in the enhancer element (EEC, see text). The 63-bp enhancer region (E-region) between –293 and –231 essential for the transcriptional activation of Cah1 under low-CO₂ conditions in light is highlighted. These chimeric constructs were transformed into C. reinhardtii cells, and the Ars enzyme activity in each transformant was measured under high-CO₂ (H) and low-CO₂ (L) conditions in light. Black and white circles represent the Ars activities in independent transformants under high- and low-CO₂ conditions, respectively. Bars indicate the median values. The number of transformants used for the Ars activity measurements is represented by n. The Ars activities in transformants carrying pCT362 and pCT37 under low-CO₂ conditions were compared with those in transformants carrying pCT34 by the Mann-Whitney U test, and the resulting P values are indicated. B, Northern-blot analyses of representative strains harboring the indicated chimeric constructs using ³²P-labeled Ars- or Cah1-specific probes.