Transcriptional repressor of CCA1 and LHY, thereby controlling photoperiodic flowering response. Involved in the positive and negative feedback loops of the circadian clock. With RVE8, forms a negative feedback loop of the circadian clock (PubMed:21483796). Expression of several members of the ARR-like family is controlled by circadian rhythm. Proteolytic substrate of the E3 ubiquitin ligase SCF(ADO1) complex. 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. Negative regulator of shade avoidance response. Involved in the inhibition of leaf expansion in shade avoidance response. Interacts with ADO1 and ADO2 (PubMed:15310821, PubMed:18562312). Interacts with SPY (via N-terminus) (PubMed:31899321). Phosphorylation varies throughout the diurnal cycle and enhances ADO1 binding. O-fucosylated by SPY (PubMed:31899321). O-fucosylation promotes APRR5 proteolysis (PubMed:31899321). 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. Belongs to the ARR-like family. Lacks the phospho-accepting Asp (here Glu-102), present in the receiver domain, which is one of the conserved features of two-component response regulators (ARRs) family. Extended N-terminus.