Functional Relationship of GBF1 with HY5 and HYH in Genome-Wide Gene Expression in Arabidopsis

Transcriptional networks play important roles in the regulation of biological processes through coordinated activation or repression of downstream target genes. Arabidopsis bZIP transcription factors, GBF1, HY5, and HYH, interact and heterodimerize with each other to form the regulatory network in photomorphogenesis. The genome-wide direct target genes of GBF1 and the roles of HY5 and HYH in controlling GBF1’s genome-wide DNA binding ability have been shown earlier. However, the GBF1 regulated genes at global scale, and how HY5 and HYH modulate GBF1-mediated genome-wide gene expression remain unknown. Here, we report the genome-wide gene expression profile in gbf1, gbf1 hy5, and gbf1 hyh mutants. Our results suggest that HY5 and HYH antagonistically regulate GBF1-mediated global gene expression. We validated the microarray analysis with independent qPCR analyses. Functional analysis of GBF1-regulated genes validates previously known roles of GBF1 in important biological processes. Furthermore, the data also highlight possible novel role of GBF1 in several other biological processes. The previous ChIP-chip results and this transcriptome data together demonstrate the complex transcriptional regulatory mechanism of these transcription factors, GBF1, HY5, and HYH, in photomorphogenesis.