Coordination of the maize transcriptome by a conserved circadian clock

Since transcriptional regulation is a fundamental aspect of circadian systems, genes exhibiting circadian expression were identified in the sequenced maize inbred B73. Of the over 13,000 transcripts examined, approximately 10 percent displayed circadian expression patterns. The majority of cycling genes had peak expression at subjective dawn and dusk, similar to other plant circadian systems. The maize circadian clock organized co-regulation of genes participating in fundamental physiological processes, including photosynthesis, carbohydrate metabolism, cell wall biogenesis, and phytohormone biosynthesis pathways.Circadian regulation of the maize genome was widespread and key genes in several major metabolic pathways had circadian expression waveforms. The maize circadian clock coordinated transcription to be coincident with oncoming day or night, which was consistent with the circadian oscillator acting to prepare the plant for these major recurring environmental changes. These findings highlighted the multiple processes in maize plants under circadian regulation and, as a result, provided insight into the important contribution this regulatory system makes to agronomic traits in maize and potentially other C4 plant species.Plants match their physiology to daily and seasonal environmental changes through the circadian clock, an internal timekeeping mechanism that regulates a wide range of plant behavior. Overt circadian rhythms in plants include rhythmic leaf movements, stomatal conductance, and growth [1]. Rhythms are maintained with a period of approximately 24 hours in the absence of environmental cues and over the normal range of ambient temperatures. The circadian system enables plants to anticipate and synchronize their physiology to the recurring environmental changes brought on by day and night. The consequence of proper clock and environment synchronization is optimized fitness [2,3]. Beyond the daily control of plant biology, circadian rhythms also allow