Proline Rich Protein 9 (PRR9)

The core mechanism of the circadian oscillators described to date rely on transcriptional negative feedback loops with a delay between the negative and the positive components. In plants, the first suggested regulatory loop involves the transcription factors CIRCADIAN CLOCK-ASSOCIATED 1 and LATE ELONGATED HYPOCOTYL and the pseudo-response regulator TIMING OF CAB EXPRESSION 1. TOC1 is a member of the Arabidopsis circadian-regulated PRR gene family . Analysis of single and double mutants in PRR7 and PRR9 indicates that these morning-expressed genes play a dual role in the circadian clock, being involved in the transmission of light signals to the clock and in the regulation of the central oscillator. Furthermore, CCA1 and LHY had a positive effect on PRR7 and PRR9 expression levels, indicating that they might form part of an additional regulatory feedback loop.