A type II topoisomerase that seems to play a critical role in chloroplast nucleoid partitioning by regulating DNA topology. DNA gyrase negatively supercoils closed circular double-stranded DNA in an ATP-dependent manner. ATP-dependent breakage, passage and rejoining of double-stranded DNA. Made up of two chains. The A chain is responsible for DNA breakage and rejoining; the B chain catalyzes ATP hydrolysis. Ubiquitous. Up-regulated during seed germination and leaf expansion. Belongs to the type II topoisomerase GyrA/ParC subunit family.