GSE158898
The impact of the genes BBX32 and HY5 on the high light - responsive transcriptome of Arabidopsis thaliana
Exposure of mature fully expanded leaves of Arabidopsis to a 7.5 fold increased light intensity  above  growth light conditions (high light; HL) tirggers stress defensive responses  but also initiates cellular processes, that if such conditions persist, can lead to increased photosynthetic capacity. This process is called dynamic acclimation. By using variational Bayesian state space modelling on eariler GEO deposited time series HL data (see GSE78251) a gene regulatory network of (co) transcription factor genes was inferred. The most connected gene in this network is BBX32, which was subequently shown  to be a negative regulator of dynamic acclimation. Also present in the inferred network is HY5, which is known from studies on seedling photomorphogenesis to be antagonistic in its action to BBX32. Subsequently, it was demonstrated that HY5 is indeed a positive regulator of dynamic acclimation.  This RNAseq-based study seeks  to provide gene expression data that will help to link the immediate impact of these genes on the HL transcriptome to the longer term (several days) physiological manifestation of dynamic acclimation. Overall design: Arabidopsis thaliana (genotype Col-0) that over-express BBX32 (BBX32-10; Holtan et al. (2011) Plant Physiology 156: 2109-2123) and are null for HY5 (hy5-2; Ruckle et al. (2007) Plant Cell 19: 3944-3960) produce the same degree of inhibition of the quantum efficiency of photosynthetic elecron transport upon sustained expsure to HL, both genotypes failing to undergo dynamic acclimation.  Therefore, similar cohorts of genes may be affected in short term HL exposure. Therefore, plants were exposed to HL for 3.5h and then sampled for RNA from their fully expanded leaves. low light control samples were to be run in parallel. The duration of the HL exposure was chosen because based on time sereis daat most inductio of differential expression of genes was completed after this time. These data allow for the initial validation of the gene regulatory network centred on BBX32 (as well as future iterations and variations of this network), but will also, with further analysis yet to be done,  allow the identification of key genes downstream from BBX32 and HY5 that control both initial responses to HL and the establishment of dynamic acclimation.