Abstract

The early morning is an important time period in which light and temperature signals entrain the circadian clock.  Through a high-resolution RNA-seq time series experiment, we demonstrate that there are multiple coordinated bursts of gene expression within the first two hours of light exposure, and these bursts are light and temperature dependent.  The ABA-sensitive transcription factors GBF3 and ABF3 are expressed within 16 minutes of dawn and are light sensitive even at night, suggesting that they may be involved in the fast light response in the morning.  They also show strong binding to CCA1, LHY, LNK1, and LNK3 promoters, suggesting that they may have a regulatory role in the circadian clock.   
These genes are light and temperature sensitive, and their expression dynamics are perturbed in mutants of genes involved in red and blue light sensing (phyAphyBcry1cry2 ) and the circadian clock (prr5prr7prr9 ).  We develop a gene regulatory network to explain how these bursts of expression are regulated in the early morning and find predicted regulatory interactions that are consistent with transcription factor binding data.  We find that prr5prr7prr9 and phyAphyBcry1cry2  both show a delay in the expression of morning genes and an elevated expression of genes that are usually expressed at high temperatures.   However, these mutants have opposite effects on small subnetworks involved in temperature and ABA signalling.  This suggests that these mutants produce the same transcriptional output, but operate through different pathways, a potential mechanism for encoding robust responses to light in the morning.
The abstract should be fewer than 150 words and should not contain subheadings. It should provide a clear, measured, and concise summary of the work. If the biological system (species names or broader taxonomic groups if appropriate) is not mentioned in the title, it must be included in the abstract. (Note: 150 is very short!  The abstract below is already 107!)