Single-stranded DNA-binding protein that functions in both chloroplasts and nucleus. In chloroplasts, maintains plastid genome stability by preventing break-induced and short homology-dependent illegitimate recombinations. In the nucleus, is recruited to a distal element upstream of the kinesin KP1 to mediate the transcriptional repression of KP1. Can bind double-stranded DNA in vivo. Homotetramer. Can localize to both chloroplast and nucleus. By salicylic acid (SA). No visible phenotype under normal growth conditions. May be due to a competing acceptor splice site. Belongs to the Whirly family.