Figure 1.

5′ deletion analysis of the FTR1 promoter region. A series of 5′  deletions from −1179 to +58 of FTR1 promoter region were amplified by PCR and fused to the Ars reporter gene in pJD54, and transformed into the arginine requiring C. reinhardtii strain CC425 along with pArg7.8. Arginine independent colonies were transferred to +/− Fe TAP plates and sprayed with 10 mM XSO₄ to visualize arylsulfatase activity. FtrD5 was constructed by fusing the −1179/+58 fragment lacking the −291/−254 region to pJD54. The fraction of arylsulfatase expressing colonies among the arginine independent colonies is expressed as Ars⁺/Arg⁺; +Fe and −Fe indicate growth on +/− Fe TAP plates, and (+) and (−) indicate expression of the arylsulfatase gene. The cotransformation frequency was tested by PCR from 16 random selected Arg independent transformants.