PRR9 (APRR9, At2g46790; UniProt Q8L500) curation notes

2026-10-06: initial review (module plant_circadian_clock_oscillator)

• Fetched with just fetch-gene ARATH Q8L500 --alias PRR9 (UniProt gene name APRR9; folder and
  gene_symbol use the standard symbol PRR9).
• Falcon deep research (just deep-research-falcon) failed (provider exit code 1); no
  deep-research file. The review is based on cached publications.

Key findings

• PRR family transcripts peak sequentially after dawn: PRR9 -> PRR7 -> PRR5 -> PRR3 -> TOC1
  PMID:11100772.
• PRR9 transcription is light-induced via phytochrome PMID:14634162; PIL1 is needed for maximal induction PMID:16891401.
• Repressor of CCA1/LHY PMID:20233950.
• TPL/TPR corepressor and HDA6 recruitment PMID:23267111.
• Also occupies PRR5 output targets PMID:23027938.
• Genetics: the prr9 prr7 prr5 triple mutant is arrhythmic in LL PMID:15767265.
• Flowering output: PRR9/7/5 activate CO by repressing CDF1 PMID:17504813.

Decisions

• Phosphorelay and cytokinin-signalling IEA: REMOVE. The pseudo-receiver lacks the phospho-Asp, and these are domain over-propagation.
• DNA-binding TF activity IBA: MODIFY to GO:0001227 (repressor), consistent with the TOC1 review.
• Protein binding (Y2H: TOC1, BBX18/19, NF-YC2/4): REMOVE as uninformative.
• Red/far-red light signalling: KEEP_AS_NON_CORE.