Molecular and transcriptional structure of the petal and leaf circadian clock in Petunia hybrida

The plant circadian clock coordinates environmental signals with internal processes. We characterized the genomic and transcriptomic structure of the W115 clock in leaves and petals. We found three levels of evolutionary differences. First, , and and , differed in gene structure including exon number and deletions including the CCT domain of the PRR family. Second, leaves showed preferential day expression while petals tended to display night expression. Under continuous dark, most genes were delayed in leaves and petals. Importantly, photoperiod sensitivity of gene expression was tissue specific as was affected in leaves but not in petals, and and the ortholog , were modified in petals but not leaves. Third, we identified a strong transcriptional noise at different times of the day, and high robustness at dawn in leaves and dusk in petals, coinciding with the coordination of photosynthesis and scent emission. Our results indicate multilayered evolution of the clock including gene structure, number of genes and transcription patterns. The major transcriptional reprogramming of the clock in petals, with night expression may be involved in controlling scent emission in the dark.