CYTOKININ AFFECTS STABILITY OF COMPLEX PLASTID TRANSCRIPTS IN CYTOKININ-SENSITIVE MOSS MUTANTS

The plastid DNA region covering trnR-CCG,yef 1, and psaI was cloned an d sequenced from a moss (Physcomitrella patens). It is identical in a wild-type strain and in a cytokinin-sensitive differentiation mutant, derived from it. Nevertheless, stabilities of immature transcripts fro m the ycf11-petA transcription unit differed between the two genotypes . The respective transcript patterns were influenced by cytokinin, by light, as well as by the experimental daytime. Immature transcripts of four plastid genes (ycf11, atpA, psbA, psbB) accumulated in two cytok inin-sensitive differentiation mutants when compared to the wild-type. Upon cytokinin-treatment, stabilities of these transcripts were reduc ed to wild-type levels in both mutants. As both mutants are defective in cellular differentiation but only one is defective in chloropiast d ivision, we propose that altered mRNA stabilities of these four plasti d genes may be a consequence of the mutation in budding (bud), rather than a consequence of the mutation in plastid division (pdi).