Comparison of expL3 transcript levels in Ax2 and STATa null strains. Ax2 and STATa null cells were allowed to develop until the desired developmental stages. Total RNA was extracted from Ax2 cells (shown as blue bars) at the first finger/early slug (indicated as ES), late slug (LS), and Mexican hat/early culminant (M/EC) stages, and from STATa null mutant cells (shown as pale blue bars) at the first finger/early slug (ES), migrating slug after 20 h of development (S1), and slug at 24-h development (S2) stages, and used to amplify the specific expL3 DNA fragment. The expression of expL3 in Ax2 and STATa null cells was investigated by quantitative real-time PCR. The IG7 transcript was used as a normalization control. The bar heights represent the average relative transcript level based on triplicate measurements, with the error bars. The expression of expL3 in the STATa null early slug stage was set at 1.00. Statistically differences of expression level were analyzed by Student’s t-test, which showed all p-values were less than 0.01 between Ax2 and STATa null strain at comparable stages. To amplify the specific DNA fragment, we used 0.1 μg of total RNA and the primers: expL3-Fq and expL3-Rq (see Supplementary Figure 3a for their locations). The developmental stage is shown at the bottom of each column and the name of the strain is shown below each horizontal bar.