The Ct (the number of cycles to reach threshold) results from qPCR were then analyzed by calculating the fold-change using the ∆∆Ct method: ∆Ct (treated1) = 3.245, ∆Ct (treated2) = 5.54, ∆Ct (treated3) = 1.21, ∆Ct (control1) = -0.21, ∆Ct (control2) = -5.715, ∆Ct (control3) = -1.75. The control ∆Ct’s had a mean of -2.558333 and standard deviation of 2.840125 while the treatment ∆Ct’s had a mean of 3.331667 and standard deviation of 2.166301. A box plot of these ∆Ct was created on R (Figure 8).
The ∆Ct values allowed us to calculate the ∆∆Ct to be 5.89, so the fold-change between the control and treated samples was 0.016863, indicating a sharp decrease in expression of the Bradi1g72430 gene in treated samples. A T-test performed on R revealed the p-value to be 0.04993, meaning there is a significant statistical difference in the fold-change between control and treated samples. The expression of Bradi1g72430 in roots decreases in response to IAA treatment and subsequent increased growth.