Figure 4.

Immunoblot of cellular extracts showing that the abundance of RD28 is differentially regulated by the two promoters (actin15 and cotB). Proteins (50 μg) were analyzed as in Fig. 1. (A) Crude extract of act15::rd28 cells developed on filter and collected at the times indicated. (B) Crude extracts of cotB::rd28 cells developed on filter and collected at the times indicated. With the actin15 promoter, the abundance of RD28 is greatest at the beginning of the developmental cycle. With the cotB promoter, the picture is reversed.