Transcription factor involved in controlling responses to starvation (PubMed:26263501). BZIP2-BZIP63-KIN10 complex binds to the ETFQO promoter to up-regulate its transcription (PubMed:29348240). Up-regulated by KIN10 under a phosphorylation-dependent manner. Homodimer. Forms a heterodimer with LSD1, BZIP1, BZIP2, BZIP9, BZIP10, BZIP11, BZIP25, BZIP44 and BZIP53. Interacts with KIN10 and SNF4 (PubMed:26263501). Component of a ternary complex composed of BZIP2-BZIP63 heterodimer and KIN10 (PubMed:29348240). Expressed in roots, shoots, young leaves, pollen, and flowers. Present in silique valves, vasculature and funiculi. Strongly repressed by glucose. Phosphorylated. The phosphorylation at Ser-29, Ser-294 and Ser-300 by KIN10 strongly enhances its ability to form homo- as well as heterodimers and are then essential for its transcriptional activity (PubMed:26263501). Starvation-related phenotype with reduced growth and accumulation of anthocyanins. Belongs to the bZIP family. Truncated N-terminus.