Transcriptional repressor of CCA1 and LHY, and positive regulator of LWD1 and LWD2 expression. Controls photoperiodic flowering response and temperature compensation. Involved in the positive and negative feedback loops of the circadian clock. Expression of several members of the ARR-like family is controlled by circadian rhythm. Regulated at the transcriptional level by a corepressor complex consisting of ELF4, ELF3, and LUX. APRR9, APRR7, and APRR5 coordinately act on the upstream region of the target genes to repress their expression from noon until midnight. The particular coordinated sequential expression of APRR9, APRR7, APRR5, APRR3 and APPR1 result to circadian waves that may be at the basis of the endogenous circadian clock. A number of isoforms are produced. According to EST sequences. Up-regulated by heat-shock. Phosphorylated. Phosphorylation varies throughout the diurnal cycle. Regulated at the level of mRNA maturation and alternative splicing by SKIP (PubMed:22942380) and PRMT5 (PubMed:20962777). The expression of APRR9, APRR7, and APRR5 requires the presence of LWD1 and/or LWD2, indicating the existence of a positive feedback loop within the circadian clock (PubMed:21357491). Belongs to the ARR-like family. Lacks the phospho-accepting Asp (here Glu-89), present in the receiver domain, which is one of the conserved features of two-component response regulators (ARRs) family.