Analysis of Circadian Transcriptional Networks in Brassica Rapa Elucidates Temporally Regulated Abiotic Stress Modules

One of the most startling examples of plant preparedness is the anticipation of tomorrow. This ability to anticipate the arrival of sunlight and subsequent warming is dependent on an internal biological clock. The widespread occurrence of an endogenous circadian oscillator across diverse taxa suggests that there is a fitness advantage in entraining internal processes to the external environment. A recent examination of the Brassica rapa genome revealed that following triplication and fractionation circadian clock genes have been preferentially retained, suggesting that retention of dose-sensitive circadian clock genes has provided the tools for the evolution of increasingly complex clock mechanisms. To begin to address this, we have performed an RNA-seq circadian time course experiment that provides the first comprehensive examination of the circadian transcriptome in B. rapa.  

The circadian regulation of abiotic stress response results in time of day dependent transcriptional and physiological responses. Single time point experiments following abiotic stress treatments neglect the temporal regulation of the response and can lead to an underestimate of the complete response. To examine the drought transcriptome in the important crop B. rapa, we have measured changes in gene expression and physiology over a two day drought time course experiment. A comparative network-based approach was used to identify temporally regulated abiotic stress responsive modules that are correlated with various physiological measurements. These trait-correlated modules will be compared to circadian regulated modules to identify hub genes that contribute to the circadian regulation of drought response and candidates for marker assisted breeding.