Plants have evolved several mechanisms for sensing increased irradiance, involving signal perception by photoreceptors, and subsequent biochemical and metabolic clues to transmit the signals. This retrograde signaling controls nuclear gene expression. We used microarrays to detail the gene expression response to increased irradiance in three photosynthetically diverse accesssions of Arabidopsis thaliana. Overall design: Complete Arabidopsis rosettes of three accessions (Col-0, Ts-1, and Ga-0) were harvest after an irradiance increase from 100 to 550 μmol m-2 s-1 on day 25 after sowing. For all three genotypes, rosettes of nine plants per genotype were harvested on the day of the irradiance increase, 1 hour (1h) after the start of the photoperiod and flash-frozen in liquid nitrogen. For the Col-0 accession, nine rosettes were additionally harvested on the day of the irradiance increase 3.5 hours (3.5h) after the start of the photoperiod, and again one day later, at 1 hour after the start of the photoperiod, so 25 hours (25h) after the irradiance increase.