Plastid DNA of the moss Physcomitrella patens has been sequenced. An open reading frame (ORF 315) was identified downstream from rbcL, between trnR-CCG and psaI. This ORF shares homology with zfpA, a putative regulatory gene in Pisum sativum. The moss ORF is preceded by a Shine-Dalgarno sequence, two plastid promoter consensus sequences, and three TATA boxes. A specific probe detected three transcripts of low abundance in the wild-type moss and a cytokinin-sensitive chloroplast mutant. Steady state levels of zfpA transcripts were different in the two genotypes. In mutant protonemata treated with cytokinin, steady state levels of the largest transcript decreased significantly.