Controls photoperiodic flowering response. Component of the circadian clock. Controls the degradation of APRR1/TOC1 by the SCF(ZTL) complex. Expression of several members of the ARR-like family is controlled by circadian rhythm. 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. Interacts with APRR1/TOC1 (via N-terminus). A number of isoforms are produced. According to EST sequences. Expressed with a circadian rhythm showing a peak in the evening. Phosphorylated by WNK1; during the night. Phosphorylation is required for optimal interaction with APRR1/TOC1. Shorter clock period but no effect on clock phase. Belongs to the ARR-like family. Lacks the phospho-accepting Asp (here Glu-116), present in the receiver domain, which is one of the conserved features of two-component response regulators (ARRs) family.