Validation of circadian microarray data by RT-PCR. Expression data from two independent time courses (blue = microarray; red = RT-PCR) for randomly chosen (a-c) high amplitude (At1g06460, At1g69830, and At5g12110) and (e-f) low amplitude (At3g22970, At1g45688, and At3g04760) circadian-regulated genes. Amplitude classification is based on microarray analysis . For panel f, RT-PCR and microarray data are plotted on the left and right y-axes, respectively. White and gray shading represent subjective day and night, respectively.